Guide to wood flooring underlay

When considering a wood based floor covering you may require an underlay. Let’s look at the different types and explain a little about each..

The only situations that underlays are needed is when a floating floor is being installed. A floating floor means that the floor covering isn’t permanently fixed down to the ground underneath it. Underlays are generally not recommended or needed for solid wood floors.

All laminate and a lot of engineered floors are what’s known as ‘floating floors’. Some engineered wood flooring can be installed both floating and glued or nailed down to the sub-floor. In these cases, the final decision rests with yourself and installer as to the best installation method to use that suites the property i.e. If you have a sub-floor that is part solid and part wood floorboards, you may decide to opt for the floating method as this can be far easier to do. If you are installing the floor by fixing it to the sub-floor, an underlay must not be used.

If you will be floating your new floor there are several types of underlay available, all with great properties that will suite particular requirements.

Roll underlay

Wood floor underlay on a roll is often around 3 mm thick. The thin thickness is sometimes seen as a negative. However, in the world of wood flooring, less movement is better. Roll type underlays tend to compress, giving slight absorbent properties, but if they were any thicker, this could create excessive movement resulting in problems with any wood based floor covering further down the line. These underlays can have exceptional acoustic properties but do not be mistaken that they will prevent noise altogether. They do also give some insulating benefits. All of the points mentioned are very much dependent on the quality of underlay you purchase. You should compare the specification of the underlays before you buy i.e. Decibel ratings and insulation ratings.

There are four basic types of roll underlay..

Silver Underlay with built in vapour barrierThe first being produced with a built in vapour barrier or DPM (glossary). A vapour barrier or damp proof membrane, which can be a slightly misleading term, will only be effective if the relative moisture content of any sub-floor does not exceed 75% (That’s relative moisture, not direct moisture!). A vapour barrier should not be considered a method of water proofing! If the moisture content of the floor exceeds the % mentioned, you can expect to have a damp musty smell before long and eventually the trapped moisture will make it’s way through the vapour barrier and start to work it’s way into your new floor, resulting in all sorts of problems.

These vapour barriers are produced to prevent moisture from a sub-floor effecting your new floor covering (within specific parameters as mentioned above) . These types of underlays are designed to be used on all ground floors. More and more flooring manufacturers are now requiring an underlay with a vapour barrier be used on suspended timber floors (floorboards, chipboard, ply board) if they are on the ground floor. You should check the installation literature of your chosen wood flooring.

The second type of underlay is produced without a vapour barrier but is essentially made from the same quality material as above. Although, it must be noted that most manufacturers are now phasing out this type of underlay and favouring the blanket production of underlays with a built in vapour barrier. They will look very much like the underlay in the picture above but without the silver, gold or transparent membrane. These are ideal for first floor and upward installations. It’s worth mentioning that these thinner underlays, although marketed as helping to even out sub-floors, do not have brilliant levelling properties. As much work as possible to make any sub-floor even is recommended. It’s easy to be sold an underlay that will not perform, so heed this advice. There is very little difference in an underlays insulating properties and decibel ratings between one with a vapour barrier and one without, although this again is used as a marketing tool. Please note, there is nothing wrong with using an underlay with a built in vapour barrier on upper floors of a property. However, be aware that there is next to no gain from doing so.

White Underlay without a vapour barrier

The third type of underlay commonly referred to as White Foam Underlay (pictured on the left). This is generally around 2 to 3 mm thick and is essentially a very thin lightweight foam. Generally the cheapest of all the wood floor underlays. It has very little insulating properties or sound reduction properties but is suitable as a budget underlay.

Foam cantilever underlayThe forth wood underlay is essentially the same as the roll underlays described above but this is boxed and not on a roll. It is still around 3 mm thick but comes in a folded fashion. This underlay is commonly known as a ‘combi’. Due to the fact they also incorporates a built in vapour barrier. This type offers very similar insulation properties to the first example.

All of the underlays above are perfect for laminate and engineered floors. They’re easy to fit and can be cut simply with a utility knife. They can be used on top of solid floors, floorboards (caution regards cupping/crowning ~ please refer to our glossary or sub-floor prep), ply board, chipboard and pre-finished floors such as tiles or vinyl. Again, an even sub-floor is absolutely key to any flooring installation.

The insulation and sound reduction properties have not been shown here as this is a broad guide to the different types of underlays and not specific manufacturers. This should be confirmed with your supplier. All ground floor underlays should be taped at the seams to prevent residual moisture from getting through. Many will come with they’re own integrated tape but some don’t. Make sure your supplier has taken this into account and provided the tape with your purchase!

Block board underlay

Picture of block board fibre underlayBlock board underlay can be made with different materials like fibres, mixed wood composite i.e. cork/chipboard particles) and light weight polystyrene material. They typically range from 5 mm to 7 mm thick.

The main advantage of these types of underlays is they’re levelling properties. Do not misunderstand. Due to clever marketing language, it is easy to fall into the trap that this underlay will solve all your sub-floor problems. If your sub-floor is extremely uneven, this will not be solely resolved by purchasing block board underlay. As much sub-floor preparation work should be carried out as possible. However, if you have slight imperfections, this type of underlay is very good at absorbing these. You may find that time and usage of your room is required for this underlay to bed in. Initially, the floor may feel slightly spongy to the feel.

This is a picture displaying a separate vapour barrier Block board underlay does not come with a vapour barrier. If you are planning on using this type of underlay on a ground floor, a separate vapour barrier should be purchased and installed underneath the block board. Care should always be taken to ensure there is no sharp objects that will puncture a separate vapour barrier once installed. For example protruding nails should be sunk below the surface and grit should be thoroughly removed. A vapour barrier should always be lapped up all perimeter walls by several inches when installed.

 

© Copyright 2013 Wes, All rights Reserved. Written For: Fitmywoodfloor
About

I am a Pergo trained professional installer of 20 years. I've been up close and personal with lots of floors and have the knobbly knees to show for it...Should you have any questions or comments please feel free to add them below. Thanks for taking the time to call by and I hope the information you've found has given you some insight!........................................................................................................................................................................“When you click on links to various merchants on this site and make a purchase, this can result in the site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network, amazon.com, amazon.co.uk, amazon.fr, amazon.de, amazon.it, amazon.ca, affiliate window network.” This statement is to comply with current internet regulations regarding transparency to consumers.

Posted in Engineered floor fitting, Engineered wood flooring, Flooring accessories, Laminate floor fitting, Laminate flooring, Underlays Tagged with: , , , , ,
  • Linda Bullimore

    Hi Wes
    We shall be installing a solid wood floor by secret screwing into the tongues. Should we always install the bitumen paper beforehand or is it only needed if you have doubts about damp? Also around the edges of the floor there was parquet stuck down with bitumen which , after removing the parquet squares, has left some small sticky areas on the floor. Will this be OK to leave under the new floor or might it do damage? It is not a large amount.
    I have found your replies to other readers really useful so thank you.
    Linda

  • Hi Linda,

    I’m glad you’ve found my replies of some help 🙂

    It would be my advice to put down bitumen paper regardless. Can you tell me what the sub-floor is please?

    You should carry out moisture checks on the substrate to avoid any expensive issues. Bitumen paper is not a DPM.

    The bitumen residue won’t be an issue. Scrape off any lumpy areas so the surface is flat, place the bitumen paper over the residue, and crack on. But please do answer my question above.

    Kind regards,

    Wes.

  • Linda Bullimore

    Hi Wes
    Thanks for the info. We are laying the floor over wooden floorboards which are on joists. It is a standard suspended floor construction with a void below and air bricks in the walls. The void has a concrete base and it seems very dry down there. So would we still need to do a moisture check?
    Linda

  • Hi Andrea,

    I assume they are doing you a deal on the comfort http://www.luxuryflooringandfurnishings.co.uk/accessories/underlay/engineered-flooring-underlay/comfort-silver-laminate-and-wood-flooring-underlay-3mm-thick.html (It’s listed at £16.99 but there’s no others that are similar in price and description. I’ve used this type of underlay many times over the years and never had a problem. Typically, you’ll loose a little in acoustic properties compared to better more expensive underlays. Would you notice, probably not.

    I do question their use of the term DPM and the wording in the product description “this underlay has a built in DPM (Damp Proof Membrane) for added protection against any damp.” ‘Damp’ is a very generalized term in itself. To be more concise, these type of underlays only protect against moisture vapour or residual building moisture of 75% relative humidity of less (this refers to concrete floors). Strictly, anything above that may be too much for that underlay to handle.

    I will also add, with a 3 mm roll underlay, the sub-floor really does have to be very flat. A 3 mm underlay will not help out much at all against unevenness.

    The foam component will not disintegrate, it will – over time – compress, but it won’t turn to dust in the way carpet underlay does.

    You are not over worrying. A good amount of research and thought at this point of the project is absolutely key to a successful outcome. Just slapping any underlay down is foolhardy.

    Can I ask what the sub-floor is please? I.e. Concrete, Ashpalt, wood floorboards, chipboard etc..

    Regards,

    Wes.

  • Andrea Standivan

    Dear Wes,

    Thanks so much for the info. We are thinking now of getting the gold backed 5mil roll which is 29.99 (hopefully will do a deal on that too as a thicker one might be slightly more forgiving and longer lasting).

    The floor is concrete, with self leveling compound on top (which my husband did). It has a few minor imperfections and he asks what is the best way of getting rid of a few high points..should or could we grind down the levelling compound or is it better to take off a bit off the underside of the engineered wood as you go along…it’s not major but could be improved. We have done the best job possible with a wonky floor and don’t want to put more levelling compound down as will raise the levels too much.

    Thanks so much for taking the time to look into our queries. You are a star!

    Regards Andrea

  • Hi Andrea,

    Don’t take any wood off the underside of the flooring. Your husband will need to grind down the high spots, and bring up the low spots. Unfortunately, It’s a little trickier to work with self levelling than the name suggests.

    He could use a basic 4 inch grinder, install a diamond cup disc (Link below), and a grinder extraction hood. Then attach a vacuum to the hood. Without extraction, you wouldn’t believe the dust generated from this process! I also can’t guarantee how long the grinder will last, especially if you need to take a lot off. We use commercial grinders, diy range aren’t really up to the task, but well worth a try.

    Cup disc link – http://www.screwfix.com/p/erbauer-double-grinding-cup-105-x-22-23mm/58310?kpid=58310&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&cm_mmc=Google-_-Shopping%20-%20Tools-_-Shopping%20-%20Tools&gclid=Cj0KEQjw2_23BRDb_qbvzK3X8M8BEiQAg87AF6Y1N3F1-JGC5iQ1ZdljrYXLF6bx69c8Qdhwlx7oQFwaAvO08P8HAQ

    An example of a grinder hood (but needs to suite your particular grinder – http://www.amazon.co.uk/Makita-195239-9-Collecting-115mm-Grinders/dp/B00G4RBGRY/ref=sr_1_fkmr0_2?ie=UTF8&qid=1459613667&sr=8-2-fkmr0&keywords=grinder+extraction+hood

    Kind regards,

    Wes.

  • Alex

    Hi Wes … my turn to ask for some assistance please.

    I am constrained by a budget, although not so constrained as to seriously hamper the project from the start – I have re-carpeted before & found that you’re better off buying a cheaper carpet & thicker, better quality underlay, than spending more on the carpet & trying to save on the underlay … I was applying the same principal to this project!

    I have bought some 7mm or 8mm thick engineered flooring & it is going down over my old floorboards. It’s all being fitted downstairs & my house is a 1930’s semi, made of engineering brick – so in Summer it is generally too warm & in Winter it can hold the cold. The crawl space is about 1.5ft to 2 ft deep & is earth underneath, not solid concrete (I assume the house is built on foundations, as there’s never been any subsidence or damp issues). My floorboards are about 25
    mm thick & laid over wooden joists. Some of the articles I’ve read tell you to use a vapour barrier / DPM, some say not to – as it can result in damp forming underneath & affecting the floorboards, or even worse, the joists – so obviously I’m keen to get this right, not to have to take it all up in a year or 2 & carry out some major remedial works!! Also, the floor will be floating, not fixed down.

    After scouting around, I was thinking of using either the Vitrex fan-fold underlay board (http://www.screwfix.com/p/vitrex-fan-fold-underlay-board-9-6m/9035h),
    Techni boards (I think they’re a thicker foam than the vitrex), the solid wood fiber type underlay boards (http://www.screwfix.com/p/vitrex-premier-wood-laminate-underlay-boards-5mm-9-76m-green/68038), or an XPS foam underlay. (sorry about the Screwfix links, I don’t work for them, they were just the links google gave me).

    I’m not entirely sure which would be best, so your advice would be welcome – the floors themselves are knocking on a bit & are definitely not as even as they once were. There’s no serious issues, but I definitely need something that will help level them out. I’ve also seen elsewhere, you’ve mentioned visqueen & bitumen paper (http://www.birbek.com/products/builders-floor-lining-kraft-paper.html) … would it be a good idea for me to get some bitumen paper to lay 1st, instead of a vapour barrier, or will this potentially have the same impact I mentioned above?

    Thanks in advance.
    Alex.

  • Hi Alex,

    And assistance will be given 🙂

    I’m also of the same opinion as a lot of flooring tradesmen in relation to not feeling fully comfortable using a vapour barrier over floorboards. However, I’ve never actually seen floorboards and/or joists that have rotted as a direct result of using a vapour barrier.

    Certainly, my preference in such circumstances would be to use bitumen paper (this will act as a good vapour barrier while not fully restricting moisture like a full DPM sheet), then an XPS type underlay like ‘Vitrex premier board’. This type of underlay is absolutely excellent (do trust me there) and will absorb a lot. Although, and particularly if you are running your new floor covering in the same direction as the floorboards, if the floorboards are very out of shape, you should run an electric plane over the high spots with a view to helping the underlay. Baring in mind, after you put a vapour barrier over the top, there is the ‘potential’ for them to change shape (cup/crown) further down the line. Hence, you’d want to give the underlay the best chance to absorb any future changes.

    If you go for the XPS type underlay, do expect it to feel spongy initially when you walk on the floor. This will subside the more you use it and the underlay beds in.

    I hope that’s been of some use Alex and all the best with your up coming project.

    Regards,

    Wes.

  • Alex

    Wes,

    Thank you very much for your advice & quick response – If only all my DIY projects could get done so quickly!!

    I have ordered the bitumen paper. As it turns out, that company are local to me, so I will pick it up from them, making it even cheaper – bonus! Thank you for the article regarding the vapour
    barrier / DPM difference – the existing floorboards are perfectly dry & no damp issues at all & they’ve been perfectly ok for the last 85 years, so I think – as you say; the bitumen paper will act as a perfectly good vapour barrier without the full restrictions of a full DPM.
    If they’ve lasted that long without my “assistance”, now is probably not the best time for me to think I know best & “help” them!

    I will go over the floorboards with a hammer & get rid of any protruding nail heads, then give it a sweep & a vacuum to make sure it’s all ready for the bitumen paper to go down.
    I will be laying the laminate at 90 degrees to the existing flooring,
    not in the same direction.

    The premier boards you have suggested are the “solid” ones. Are they better than the XPS foam ones like techni board, even though they are both 5mm thick? I understand that the foam will feel a little spongy at first, but I made an assumption that spongy was better on an older floor like mine, as it will let the underlay settle & even out any imperfections. Is that a poor assumption
    to make & should I stick to the solid type premier boards?

    Also, as far as expansion gaps go, I have read that it should be 10mm either side. Is that the correct figure, or should it be 10mm in total? I had thought about running the oscillating saw along the bottom of the existing skirting boards, to give a suitable expansion gap, but before I go starting that I thought it’d be best to ask someone that knows what they’re doing, not rely on me hoping that I was right!

    Thanks again.

    Alex.

  • Hi Alex,

    The XPS underlay ‘type’ and Vitrex premier boards are one and the same. They are essentially highly compressed polystyrene. It ‘may’ only initially feel spongy as it won’t bed in instantly. The sponginess, if any, will subside and the floor will feel firmer over time. Providing, any undulations don’t exceed around the 4 mm mark.

    To confirm, an XPS underlay is not really foam, in this context. Foam refers to a polystyrene type underlay that has many air pockets and is springy i.e. white foam underlay – roll. XPS, to draw comparison, is foam (so to speak) with few air pockets. In other words it is more densely packed with polystyrene pellets. This type of underlay is very light weight, and extremely absorbent in relation to undulations. However, the top side, where the bottom of your planks come into contact with it, will stay flat. Stick with Vitrex premier board/XPS type. To confirm, they are the same thing.

    10 mm gap on all sides. NOT 5 mm on all sides.

    In my opinion, using an oscillating saw for such a task will take a very long time, and chew through a lot of blades (Not cheap). It would be far easier and less time consuming to remove the skirting boards. Of course, that is unless we’re talking massive skirting boards here. We use a Jamb saw to cut skirting boards in-situ, and an oscillating saw to finish off corners, get behind pipes, and generally awkward places. A word of caution, please do be very careful of hidden pipes and electrical wiring. I’m sure you know about that, but that statement may well be important for other readers.

    The obvious other option, as I’m sure you’ve considered, being beading/moulding etc.

    Regards,

    Wes.

  • Alex

    Morning Wes & thanks again for your help – it really is
    appreciated.

    Thanks for clarifying & it’s good that you recommend the
    XPS / Vitrex, as the compressed polystyrene were the ones I felt were most suitable. I’m not sure if I’d got the
    wrong end of the stick somewhere or if fiber type boards do exist, but I felt more confident with a non-moisture absorbing material, as I could see more of a potential for an issue with fiber boards, if moisture did occur in the future.

    I was fully expecting the sponginess to be like new carpet
    underlay – within a couple of months it’ll bed down & compress where it needs to, as the floor is used & finds it’s ‘level’, so I won’t worry too much if it does feel that way for a while.
    I assume it’s ok to use the floor “normally” straight away – I.e. to put furniture back etc.?

    As far as the underlay goes, I have looked at 5mm & 6mm – the 6mm is a roll rather than uniform size boards, but it’s XPE. Do I need to tape the XPS boards along the seams like you do with carpet underlay? If so & if XPE is very similar, the roll may be the easiest way forward. I’ve also seen suggestion of fixing the underlay in place with spray adhesive, but I wasn’t sure why that would be necessary …

    Thanks for clarifying the gap as well – the XPS underlay
    packaging I saw said a 5mm gap around all edges for expansion & other info I’d seen said 10mm, so I’ll make sure I leave a 10mm gap. Actually, thinking about it, do they mean that the underlay should overlap the laminate?

    Yes – I fully agree with you that the oscillating saw option
    will be long winded, frustrating, time consuming, blade killing & dust generating! Unfortunately that’s still the easiest & most viable option … The skirting boards are
    old ones (original I think, as the ones I have managed to remove are held in with old flooring type iron nails; the ones with a 90 degree head, that taper to a point – but they are all nailed into wooden wedges driven in between the bricks). They are about 6.5” tall, the old lime plaster is not likely to stand up to too much drilling if I start moving them to re-locate them & I have no wish to start rendering & re-plastering everything just yet. Also, because of how old they are, the nails that hold them in were well & truly driven in, so you end up pulling them about 6” away from the wall at the nail point – which is about 2 foot at the far end of the board … that means draining the central heating system, removing a few radiators & also cutting into the central heating pipework to be able to remove
    the pipes to be able to pull them out that far … you see my predicament with that one!!
    I will be finishing it all off with beading, but not only do some of the radiator pipes limit the size of the beading I can use, but my hallway seems quite narrow because of it’s high ceiling & I think that 20mm / 25mm beading
    on each side will make it seem even more so, even though it won’t actually be altering anything.

    I fully agree with your caution – the more times you put
    things like that, the more people see & pay attention to it. Unfortunately people overlook safety points like that a lot of the time, as I think they get carried away with getting the job done & wanting to get it right & they’re so focussed on doing so, they forget safety & common sense.

    With the bitumen paper, should it be laid like a DPM – i.e. leaving an upturned edge all the way around it, or will trimming it to the exact area be ok?
    Thanks.
    Alex.

  • Hi Alex,

    Your comment indeed got through, it’s just taken me longer to moderate due to work commitments.

    Fibre board underlay does exist although it does seem to be getting phased out and replaced more and more with XPS types.

    Perfectly fine to use your type of floor straight away. Crack on.

    As you’ll be using bitumen paper, no need to tape. The thick roll XPE underlays in my experience are too springy. There may well be exceptions to this but I’ve not come across any as yet.

    I’m slightly confused regards the expansion around the underlay question. I doubt they require a 10 mm gap around each board as they are unaffected by moisture. Don’t worry too much about the underlay overlapping the laminate (from beneath of course). Close is fine. You simply won’t notice.

    If you are finishing off with beading, you don’t need to undercut the skirting?? Am I reading you right there? You should however, undercut the architrave and door frames for best cosmetic appearance. Your house sounds like a prime candidate for hidden wires behind the architrave/door frames, so again, proceed with caution – Any time you are undercutting.

    Trimming the bitumen paper to the exact area will be fine. No need to lap it up the walls. It’s merely a vapour barrier.

    Kind regards,

    Wes.

  • Alex

    Hi Wes, no worries – I’m just grateful for your help. I wasn’t thinking you’d be available 24/7 to reply, but for some reason my other posts showed as waiting approval, but that one disappeared – I thought maybe I’d deleted it or something.

    Something you’ve said has just clicked into place about the underlay. I was thinking that all the underlay boards should be fitted together & taped & should ‘underlap’ the laminate by 5mm … From what you’ve said, I’ve just realised that they’re saying that the underlay boards should have a 5mm expansion gap between each one – effectively the same as a grout line around tiles! Now it makes sense to me … although I agree, they wouldn’t be affected by moisture so shouldn’t need a large expansion gap.

    I did wonder if the 6mm XPE would be a little too thick, as
    the laminate itself is only 7mm or 8mm thick; so it’s not as heavy as say 12mm thick & doesn’t need as much cushioning, or have the immediate weight to dampen the thicker laminate down quickly. I’ll stick to the 5mm, thank you.

    Yes, you were reading my intentions correctly – as bizzare as they may sound! 🙂

    My idea was to cut the bottom off the skirting so the
    underlay & laminate had expansion room underneath it & ideally I’m looking to use a really small beading just to hide the small gap under the skirting as the underlay & floor compress & find their level over time & to help prevent any draughts from it.
    This is the part I’ve thought least about – so it may be a bit of an impracticality, but if it’s just time consuming & hard work, then that I don’t mind.

    Thank you – I’ll be careful with any drilling or cutting – I
    tend to cut all power at the consumer unit anyway, just to be on the safe side, but when I moved in I had the place re-wired. All the carpets & some of the floorboards came up (hence the laminate not the natural floorboards, as some were damaged) & it took them about 2 weeks & 6 drill bits due to the engineering brick … so I’m pretty
    confident there’s nothing contravening the IEE regs at the time & nothing I’ve seen since makes me believe otherwise … but I’ll still use the tester & caution!

    Thanks.

    Alex.

  • Hi Alex,

    In that case (In relation to the underlay), I’d simply advise you to carry on and follow the manufacturers instructions.

    Fair enough in relation to undercutting and then installing a small profile bead. That’s your prerogative.

    I wish you all the best with your up coming project.

    Kind regards,

    Wes.

  • Hi Alex,

    Just a word a caution. If your original floor boards are uneven i.e. cupping/crowning, different levels etc, 6 mm ply will do little to help solve this and may well leave voids beneath the ply if they aren’t fixed correctly and/or leave the ply hugging the floorboards leaving undulations.

    You be well advised to rectify any undulations by using an appropriate smoothing compound. This will help give a flat surface which is all important when using a product like elastilon. If you don’t carry out rectification work, you will be left with voids beneath your floor which my effect the longevity and/or leave your floor extremely creaky.

    Another option would be to increase the thickness of ply to perhaps 12 mm. The 6 mm may well be fine, if the new engineered flooring is running perpendicular to the original floorboards. Voids may well not have a technical impact on a 20 mm thick engineered floor, but may still leave the floor sounding clacky in places.

    I hope that’s of some help and I wish you all the best with your up coming installation.

    Regards,

    Wes.

  • Alex

    Thanks so much for feedback. I’m very nervous about it!!

    Sorry – I was not clear. The engineered board has a 6mm wear layer of oak. The ply board i’ve been quoted is 18mm thick. The original boards do not cup at all – they are quite flat really. But they are Victorian and so a bit old and not perfectly level like a cement floor. Plan to lay the new boards in same direction as old ones but am hoping ply thick enough to accommodate that?

    I want the floor to feel solid and not creak or sound hollow.

  • Hi Alex,

    Wow! 18 mm thick ply overlay. Well you’re certainly not going to have any issues from the floorboards. Level, however, is a different thing. It’s so hard for me to give proper advice with these things as I’ve obviously not seen the area.

    Do consider the height rise, 18 (ply) + 18 (eng floor) + 3 (elastilon) = 39 mm. I’m sure you have considered that, probably a silly statement.

    As you’re going for an 18 mm thick engineered floor, it will sound and feel somewhat firm. However, elastilon is an adhesive ‘underlay’. Therefore there will be some sound transference/vibration as the floor will essentially be floating.

    I’ve actually just wrote an article several days ago that is very much relevant to your circumstances. May be worth having a read Alex http://www.fitmywoodfloor.co.uk/lowering-the-impact-sound-of-a-wood-floor/ .

    Feel free to call back with any questions 🙂

    Regards,

    Wes.

  • Alex

    https://uploads.disquscdn.com/images/b01192f448326bb9e8802108d22c7d0119d2e5a5f53e8e606f03436e7c206c8b.jpg

    Thanks again for reply. Yes, it will certainly raise the floor level!! Do you think 18mm is overkill?

    I’ve attached a photo. Boards look level but – it’s a knock through lounge-dining room and there is a small drop maybe 5mm between them. I had assumed the plywood would be laid in a way that evens this out. I’m not sure about a self leveling compound onto of gappy floor boards , doesn’t seem like a good idea.

    I initially wanted to secret nail wood onto ply, but was told need to allow wood to move so better to float. The Elastilon came about as as idea to reduce movement and it has good acoustic properties. Would you suggest a different underlay?

    I’ve also heard that you can put roofing felt between ply and sub floor boards to reduce vibration? Not sure what you think about that.

  • Hi Alex,

    Thanks for the pic. Your floorboards don’t look like they’re in a bad state. I think 18 mm ply is unnecessary. Baring in mind, we’d use 18 mm thick ply as a replacement to floorboards. In other words, in that context, the ply would be spanning the joists unsupported. Therefore, in short, yes, 18 mm ply overlay is overkill. 12 mm would be better, but that is only my opinion.

    As for the drop between the rooms, you could feather in a smoothing compound (applied on top of the ply). Alternatively, if one room is consistently a 5 mm drop, perhaps you could use 18 mm ply in one room and 12 mm ply in the other?

    I wouldn’t suggest an underlay at all. If would be strongly steering you towards gluing the floor to the ply using an MS polymer adhesive. This type of adhesive could also help with the transitional drop of the two room.

    Elastilon won’t reduce movement in the floor. Trust me, if the floor wants to move, it will. Elastilon, as the name suggests, has elasticated properties, and is designed to allow the floor to move (expand) as the underlay will stretch, then pull the floor back (with a view to preventing gapping) when it contracts. The exact same concept as a wood floor adhesive.

    I’ve personally never heard of using roofing felt beneath a wood floor, and I certainly haven’t found any when removing a wood floor. That’s not to say it isn’t used in certain areas of the UK etc. It’s helpful to install bitumen paper (vapour barrier) beneath the ply to help protect against moisture migration from the floorboards to the ply. I honestly can’t comment on whether roofing felt or bitumen paper would noticeably lower the impact sound. I would take a stab and say I really don’t thing you’d be able to tell either way, but I could be wrong there.

    Regards,

    Wes.

  • Gerard Patrick

    Hi Wes, I fitted good quality laminate flooring about 12 years ago. The only underlay on offer was a thin foil backed roll about 2mm thick. We have a through lounge which is always cold despite the presence of three large radiators. I’m convinced the floor radiates coldness and I’m keen to lift it and supplement the thin underlay with 7mm fibre board or similar. I’d appreciate any advice please.

  • Hi Gerard,

    I think your approach is solid and will likely bring the desired results. I will say, it’s advised to install a vapour barrier (http://www.screwfix.com/p/vapour-barrier-green-300ga-2-5-x-20m/12869) before the underlay. That is the equivalent of the ‘foil’ on your present underlay. Fibre board or any board type underlay doesn’t come with a vapour barrier.

    I’m confident replacing the current underlay for a far thicker and better quality underlay will prove to be cost effective. Of course, I say that without seeing the property etc, but trust your opinion being the one that lives there and my experience tells me 2 mm underlay has very little thermal insulation properties.

    Regards,

    Wes.

  • Gerard Patrick

    Thanks Wes, any advice concerning which product to use, there are several options and quite a difference in price. I don’t want to get it wrong!

  • Of late we’ve been using a lot of the ‘Vitrex Premier boards’ compressed polystyrene type. Again,excellent thermal properties, but there’s nothing wrong with using a thicker fibreboard type. I’m confident the results would be similar.

    You should expect to be paying between £2 and £3 per square metre.

    Hope that helps.

    Regards,

    Wes.

  • Gerard Patrick

    Thanks very much for your help.

  • Gerard Patrick

    Wes, one last question, would it be ridiculous to use two layers?

  • With that type of underlay it shouldn’t be a problem to do a double layer. If it was a springy type of underlay, like a roll type, it most certainly wouldn’t be advisable.

    I will say, if you decide to double layer, you can expect the acoustics to change. The floor may well sound a lot more clacky. It may also take a little longer to bed in. Just something to consider.

    Regards,

    Wes.

  • Hi Sarah,

    The first thing to consider is how you wish the floor to sound and feel. Directly fixing the floor to the sub-floor will provide a firm feel combined with low impact sound. The cost of direct fixing is typically more due to the required preparation, particularly on the concrete, and time taken. With this method, you generally wouldn’t place an underlay beneath the floor.

    The second option would be to ‘float’ the floor. Which essentially means installing the floor on top of an underlay. This method is typically cheaper than the above alternative as it often requires less preparation. Please note, the impact sound can often be higher than a direct bonded floor and it may not feel as firm, although, that shouldn’t be too much of an obvious problem at 20 mm thick. Do choose a good quality underlay should this method of installation be preferred.

    I’ll also add, most manufacturers will have installation guidelines packaged with the flooring. It’s always advised to follow the instructions closely.

    I hope that’s of some help.

    Regards,

    Wes.

  • Stephen

    Hi Wes,

    I am looking to move in to a new build (first floor flat) in October and I am planning (already ordered) to put 10mm Strand Woven Bamboo down (uniClick type) in a floating manner. What would you recommend as an underlay ? I am not entirely sure what the sub floor will be but I can certainly ask to find out. What would my options be either way ?

  • Hi Stephen,

    My personal opinion would be to go with an XPS type underlay like ‘Vitrex Premier Board’.

    No matter what you use, you’ll still get some noise, especially with the floating method. Please do consider your downstairs neighbour.

    I hope that’s of some help and sorry for the single sentence lecture. I’m just trying to save you and your neighbours from feuding 🙂

    Kind regards,

    Wes.

  • James Hunt

    Hi Wes, This article and its comments are a great help and source of information. My question is as follows; we have just had an extension built with a concrete base (30m2) built to current building regs and want to put down an engineered floor, the one we like to match the other solid flooring we have is an 15/3 board which we are happy with as this will be a low traffic area. We want the boards laid length ways in the room running down the room towards the window, the supplier has two underlays he is trying to get us to buy one is 2mm and the other 5mm both are non branded so have no idea of the quality. Please can you suggest an acceptable thickness, do we go roll or board and manufacturer as we want to get this right first time, also how can we tell if the floor has been laid to an acceptable quality to lay on to? Thanks

  • Hi James,

    Although you’re buying a nice thick engineered board, I’d still try to direct you away from the 2 mm underlay. You’re no doubt spending a decent chunk of money and a cheap thin underlay would be a bit of a shame really.

    The 5 mm underlay would certainly be the way to go. Obviously it needs to be a specific wood floor underlay of which I’m sure your supplier is providing.

    As the extension is new, you need to be cautious of the moisture content of the concrete/screed. A basic rule of thumb to follow, is for every 1 mm of concrete, leave a day drying time. However, this is simply just a rule of thumb. Ideally, you should get the slab tested for moisture. Current British standards methods being with the use of a humidity hood or humidity sleeves. There are other methods that would work to give an indication, excluding a pin meter.

    Once you’ve ascertained the moisture content and are happy (typically the reading would show 75% Relative Humidity or less), you would apply a vapour barrier (If your suppliers underlay doesn’t have one), and then your underlay etc.

    You should also check the sub-floor for flatness. This can often be crudely done with a 2 metre straight edge. My best advice would be to not avoid levelling/flattening work by leaving it all to the underlay. The underlay will help, but it doesn’t do miracles.

    To answer your question regards recommendations. Generally, most 5 mm ‘wood floor’ underlay will be fine. The secret really is the sub-floor.

    Roll or board shouldn’t matter. Although, I have had comments from people on here that have had bad experiences with 5 mm roll type underlays, citing it to be a little springy. Most roll types tend to have a built in vapour barrier. Durulay (Durulay timbermate excel) do an extremely good wood floor underlay. It’s only 3 mm thick but as I mentioned, the sub-floor is the key. If you decide to go for a board type, my recommendation would be an XPS type like ‘Vitrex Premier Board’ (I’m sure you’ve seen me mention it 😉 Do bare in mind, this won’t have a vapour barrier, therefore, consider buying a separate vapour barrier (300 gauge) from somewhere like Screwfix or Wickes etc. The XPS type isn’t effected by moisture, but I’ve not had confirmation that is will totally prevent the passage of moisture vapour.

    I hope that’s of some help James. All the best with your up coming project.

    Kind Regards,

    Wes.

    P.S. Glad the article and comments have been of help 🙂

  • James Hunt

    Hi Wes,

    Thank you, you have made everything very clear. I am taking your advice and going for the boards with a vapour barrier.
    Screwfix has everything I need as usual, just love that supplier.
    Again thank you for the detailed and practical advice.

    Regards

    James

  • Hi Stephen,

    Apologies for the delay in getting back to you.

    We have used the slatted type underlay, and I honestly cannot tell you why they are slatted. I can only surmise is has something to do with insulation i.e. Trapping in warm air. We’ve used it in conjunction with underfloor heating as recommended by the supplier.

    For me, both the slatted type underlay and sonic gold etc i.e. 5 mm thick roll type underlays seem to be a little spongy for my liking. The board XPS type, although can feel a little spongy initially, really does become very firm once bedded in.

    Regards,

    Wes.

  • My preference would be the XPS type as it collapses to suite/absorb high spots resulting in more contact with the flooring and less voids/air pockets, which are mostly the cause of vibrations.

    Would you notice the difference using either? I’m afraid that’s hard to say.

    Regards,

    Wes.

  • Mungo

    Hi Wes, you’ve got some really useful information on here. Im hoping you can give me a little advice. I own a top floor flat and want to put down engineered wood in one room. I need to be careful because of the lease and the flat below re. sound insulation, though generally it seems pretty good anyway (its a victorian barracks block). I also would like something that might help level the floor a little, though the fitter will work on this if necessary. Cork underlay is touted as being good for acoustics (looking at 5mm) but I cant see too much difference in db sound rating to that and the Vitrex boards you mention. So my question is – do you think there is much difference and also which of those 2 do you think would be best in terms of helping to level the floor a bit ? Any advice much appreciated !

    cheers

  • Hi Mungo,

    Cork wouldn’t compress in the same way as XPS type underlays (Vitrex Premier etc). So regards levelling, XPS every time.

    If the sub-floor has undulations and the cork struggles to absorb/bed into any high spots, you would be left with voids/air pockets beneath the floor in places. This can aid sound transmission, think drum. The idea is to minimize voids/air pockets. In other words make sure there is full contact between the bottom of the wood planks, underlay, and sub-floor. With a ‘floating’ method of installation you’ll inevitably still get some ‘clack’, but using an underlay that will compress, should greatly help this.

    If you haven’t already read it, here’s an article that may be worth a read http://www.fitmywoodfloor.co.uk/lowering-the-impact-sound-of-a-wood-floor/ … It’s biased towards ‘direct bond’ as apposed to ‘floating’, and I do appreciate the direct bond method may not be apt with regards sub-floor conditions, cost etc. Worth a read all the same.

    You could do a basic early comparison by screwing a plank to the sub-floor and placing a plank on top of underlay and test for impact sound in your particular property.

    Hope that’s of some help and glad you’ve found some good info here 🙂

    Regards,

    Wes.

  • Mungo

    Thanks a lot for the reply Wes. I appreciate it. I’ve now realised I’ve got wooden floorboards as the sub floor but with a thin layer of ply sheet thats been nailed on top. Feeling through the carpet there do seem to be some undulations and bits where there’s give. Im thinking thats where the ply has raised slightly or maybe at the joins.

    I was going to just take up the carpet and underlay for the fitter. Should I just leave the ply in place and make sure its fixed down everywhere ? I guess it was put there to try and level the floor in the first place.

    Also, I’ve also come across Acoustilay now as an underlay (square mats) which reduces noise. Its quite thick at 10mmm. Any experience of that ?

    cheers

    Mungo

  • Hi Mungo,

    It’s hard for me to comment on the undulations. I’ve not used Acoustilay 10 mm either so am unsure how it will bed in. 39 DB sound reduction is double that of the XPS types, so on paper far better.

    Wish I had first hand experience to give you my opinion. Instinct tells me to leave the ply in place.

    Sorry I couldn’t be more helpful on this one.

    Regards,

    Wes.

  • Mungo

    Acoustilay looks pretty good, though its pretty pricey ! Thanks for all the info you have given me, its good of you to spend the time.

    regards

    Mungo

  • You’re very welcome 🙂

    Regards,

    Wes.

  • Paul

    Hi Wes, Thank you for your article, it’s really helpful. We are looking at removing the laminate flooring in our ground floor living room and laying an engineered floor (20mm overall thickness with 6mm oak vaneer brushed UV oiled) over the underlying lacquered pine floorboards. We have got a couple of quotes from 2 different fitters and one says we should use an underlay (3mm) and have a floating floor and the other says to not use an underlay and glue down and nail the engineered floor to the sub-floor. When we asked each of them to give reasons for their suggested methods they both said if you don’t do it that way you will have squeaky floors. Please advise us on which method we should go for. And any other advise would be most welcome. Thanks in advance.

  • Hi Paul,

    Apologies for the delay in getting back to you.

    The two installation methods are largely subjective and cost sensitive. There’s no certainty that either method will produce squeaking. Excessive squeaking is often the by product or I should say precursor to something that has gone wrong. I say ‘excessive’ as sometimes a small amount of temporary squeaking can occur during seasonal temperature and humidity changes.

    With your particular floor covering, either method can be used to install the floor. I’ll briefly run through the differences below :-

    ‘Floating’ – Often the quicker and cheaper method of installing. Requires less attention to sub-floor preparation, although that’s not to say you can just throw the flooring on top of any sub-floor. To avoid issues such as squeaking, excessive movement etc, the sub-floor MUST be flat, sound/firm and dry. Underlays can help regards flatness, however, most people expect too much from them. This type of installation method can result in a clacky sound when walked on. Not always hugely noticeable, especially if there isn’t a direct bonded floor nearby and noting the decent thickness of your floor, however, do consider this.

    ‘Direct bond’ – Often the longer and more expensive installation method. Will often require a decent amount of preparation and due-diligence to ensure a successful outcome. Emphasis on sub-floor preparation, in home climate and timber moisture contents prior to installation being key (Amongst an endless list). This type of installation will result in a solid firm feel underfoot and if done correctly will ooze quality.

    I hope that’s given you a little insight Paul.

    Regards,

    Wes.

  • Paul

    Hi Wes,

    Thank you so much for response, really helpful. I bet you can anticipate my next question – where can I find a list of things I need to ensure the fitters do to get a good result?

    So far I only know I need to get the flooring here well ahead of time to allow for acclimatisation and check the moisture content of the sub-floor is less than 15% (existing timber boards underlying the current laminate floor).

    What sub-floor preparation is required?

    What do you mean by in home climate?

    Thank you again for taking the time to help.

    Paul

  • Hi Paul,

    Again, apologies for the delay in my response.

    I can write you a list now..

    1, The fitter should carry moisture testing equipment (Pin CM meter (resistance) and air humidity meter), will use them, and know clearly how to explain the reading and what effect if any they may have on the installation. Moisture testing equipment like Protimeters and/or tramex are expensive. Typically, if the installer has these, he/she will have suitable equipment and know-how to carry out the installation. I say typically as there are no guarantees here..

    2, The fitter should be conscientious verging on tortured as he/she knows the consequences of the installation going wrong.

    From the above list, everything else should fall into place, we hope.

    Can I ask what direction your floorboards travel i.e. front to back of house or left to right?

    In-home climate refers to the humidity content. If for any reason the humidity levels are uncommonly high, this can lead to the new timber taking on board this moisture and expanding. We refer to that as equilibrium. If the floor is installed at such a point, once installed and the air humidity returns to it’s stable state, the floor will excessively gap as the timber contracts to match its new climate.

    Regards,

    Wes.

  • Hi Paul,

    My question was actually relating to the sub-floor floorboards. I ask as if you are planning to run your new engineered floor covering in the same direction as the floorboards, you should consider both the current condition of the sub-floor floorboards and approach you wish to take in relation to preparation work and underlayment. Cupping/crowning can greatly effect the feel, sound, and longevity of your new flooring if not approached in the correct way.

    Unfortunately, at this time I can’t recommend any wood floor installers in the London area.

    Regards,

    Wes.

  • Steven Allam

    Hi Wes, thanks for sharing this info, very useful.
    I’ve bought a flat that’s directly above a pub and I want to put an engineered wood flooring disk throughout. It’s carpeted at the moment and there isn’t much sound coming through. However the smells from the pub kitchen do come through and I want to put an underlay down that would stop this.
    I wonder if you can advise me on which underlay will be best?
    Thanks in advance for any help you can offer.
    Best wishes
    Steven

  • Hi Steven,

    I can honestly say I have absolutely no idea what underlay would be best to aid in blocking out smells. It’s not something I’ve ever been asked or ever had the need to look into.

    Sorry I couldn’t be more helpful.

    Regards,

    Wes.

  • Tomas Jumar

    Hi Wes, been reading through your webpages as I was looking for information on laying wood floor in a basement/ground floor property. It has an existing wood floor that has cupped in areas. The subfloor is poor as it is original flagstones with a poor screed and solid wood block directly glued to that. The moisture levels in the floor will exceed 70% is suspect. Therefore I am considering laying a dimply membrane and allow venting at a ventilated skirting. However can you advise if ply or OSB sheeting would be required over the membrane and what thickness this should be. Would ply still be required if engineered wood was laid instead of solid wood?

  • Hi Tomas,

    Firstly, apologies for not replying earlier.

    I find it hard to offer advice in this situation for a number of reasons. One floor has failed, all be it from what would seem like an obvious error. ‘Damp’ basements are typically troublesome. I’m not 100% a tanking membrane will fully prevent excessive humidity raises due to a lack of experience with them (I do note your use of additional ventilation).

    It may well be worth contacting the technical department of the tanking membrane company you’re dealing with for their thoughts in relation to the OSB/Ply question. I do like OSB, but my initial instinct, should lining be advised, would always be ply.

    Really sorry I couldn’t be of more help.

    Regards,

    Wes.

  • Patrick Riggs

    Hello Wes,
    We are having our engineered hardwood installed soon and after ripping up the carpet on my concrete stab I have noticed that it isn’t perfectly level. I laid a board down and I have a gap in the middle from board to concrete. Will I have to try to level it or see if my installers will or will the padding take care of it?

    Thanks!

  • Hi Patrick,

    This really does depend greatly on the severity of the unevenness. As a general rule, it’s always best to address unevenness, prior to the installation, rather than take a gamble and hope the underlay will do the job. In some cases, it can be a lot of upheaval to lift the floor at a later date.

    I also note you don’t describe the type of underlay being used. Some deal with unevenness a lot better than others, as is mentioned in the above article.

    The typical recommended amount a sub-floor is classed as appropriate to lay a an engineered floor is if the unevenness is within a tolerance of 2 mm over a 2 metre span.

    I hope that’s of some help.

    Regards,

    Wes.