Why you should NOT install a wood floor straight on top of an old parquet floor!

It’s a questioned often asked and pops up frequently in online discussions. Can a wood floor be installed straight on top of an old parquet floor? Well, the answer is clearly going to be subjective, but within the contents of this article I’ll be giving you a little of the basic science of why you should not install a wood floor on top of an old parquet floor..Read on..

Some typical and critical information you should know about old parquet wood flooring

Parquet wood block floors have been in high demand from the mid 1800’s.  A popular option for fixing them onto concrete sub-floors was with the use of bitumen adhesive. This type of adhesive had a double purpose. Early concrete sub-floors (all the way up from the mid to late 1960’s) were installed with no means of preventing them wicking moisture from the earth beneath. Common methods of moisture protection now-a-days being with the use of thick visqueen/plastic sheeting placed beneath concrete slabs. Prior to the mid 1960’s, parquet floor installers relied on the moisture blocking properties of bitumen as a barrier from moisture that would inevitably be drawn through the concrete slab, as well as using bitumen as a means of securing the blocks in place.

This was an effective method during those years, however, there was a problem with using bitumen adhesive. It perishes over time. In other words becomes extremely brittle and/or looses its strength. Which of course is to be expected when we’re talking about a material that in some cases is over 100 years old. Parquet wood block flooring moves. That is to say it expands and contracts with seasonal atmospheric changes. When the blocks expand or contract, they are applying a sheer force against an often already weakened or perished bitumen adhesive, resulting in tears/cracks/splits developing in the bitumen layer. This of course, then allows moisture from the unprotected concrete to pass.

Wood is a hardy material and will often allow low levels of moisture to pass with little or no obvious clues. Hence, many aged parquet wood floors are immediately looked at as a good sound sub-floor on which to install a wood floor. However, with the information above in mind, there is a problem..

Why you should not install a wood floor straight on top of an old parquet floor!

Everything looks fine with your aged original parquet floor. Then you install a wood floor over the top. For instance a ‘floating’ engineered wood floor, laminate, or even ply board sheeting in preparation for a Luxury Vinyl Tile.

This is often where the problems start. Sometimes within a few weeks, sometimes with a few years.

When a wood floor is installed on top of a parquet, you’re essentially putting a lid on a simmering pan. Blocking the transference of moisture from the original concrete through the parquet. This is of course providing the bitumen adhesive has failed. I’ll tell you now, an aged bitumen wood block adhesive is rarely, if ever, in tact after twenty or thirty years plus!

When our metaphorical lid is placed on top of an old parquet floor, the moisture can build up. Immediately, the parquet blocks will start to absorb this moisture like a sponge. Resulting in the blocks expanding, again, a lot like a sponge. This will typically only happen in localized areas, where the breaks are in the bitumen. Although, if the bitumen is in a very bad state, the entire area can become wet. Regardless of this effect happening in localized areas or the entire floor, Murphy’s law will inevitably kick in. As the blocks expand excessively, the accumulative effect of the expansion will come to a head. In other words, the expanding blocks will hit either well fixed wood blocks and/or perimeter objects such as walls, door casings etc. With nowhere to go, the blocks will give at the least point of resistance, and lift. This is also known as ‘tent’ or ‘tenting’. This tenting will push the new wood floor – on top – upwards. Resulting in an extremely undesirable and frankly unlivable wood floor that will without any shadow of a doubt require removal.

Should you be one of the lucky ones, and your floor doesn’t tent, you can often look forward to years of rotting wood and mouldy damp smells.

In summary

Do not take the chance and install a wood floor, of any kind, on top of an old parquet block wood floor. You have been warned!

© Copyright 2015 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 Problem floors and poor installations, Solid wood floor fitting, Solid wood flooring, Uncategorized Tagged with: , ,
  • Ian Davis

    Hi Wes
    I have lifted a parque floor which i am hoping to have re-layed in another area of the house. The floor under the parque is coated in bitumen and a little uneven. I plan to re-lay a new wooden floor over this area. Please advise would the ardex 1c and ardex NA treatment ensure that no moisture would penentrate through the bitumen to affect the new floor ? Would there be any reaction between the bitumen and ardex ? How much height would these two treatments add to the floor ? I am concerned it may raise this area of floor in relation to the surrounding rooms ?
    Many thanks
    Regs ian

  • Hi Ian,

    If you plan on ‘floating’ a new wood floor, the adrex 1C and NA will be fine. Providing there is no hydrostatic pressure. If there were no issues with the original floor, this may provide a good indication that you will be ok.

    There shouldn’t be a reaction to the bitumen, however, you should grind/remove as much of the bitumen as possible to aid with good adhesion of the DPM. I would always suggest you contact the Ardex tech department for clarification. From the horses mouth so to speak..There are also technical data sheets available from the Ardex website..

    The Ardex 1C should be applied at 250 microns (0.25 mm). The NA can be applied from a feather up to 12 mm in a standard mix. It’s really a case of how deep you wish/need to apply it, as to what it’s going to add to the height.

    Apologies for the slightly vague reply. It’s just a relatively technical thing to do (Successfully anyway). It’s not just a case of do this do that, as each property/sub-floor/project is often very different from the next.

    Regards,

    Wes.

  • Ian Davis

    Thankyou very much for the detailed reply Wes

  • Ashley Martin

    Hi Wes,

    I also have a house that was built in 1970 ish that that has a wooden parquet floor over a thin black layer (assumed bitumen) throughout downstairs. The previous owner’s carpet was stained in 2 rooms which I put down to ‘sweating’ with the underlay but could in theory be the issue explained in your article.

    The parquet has lifted in the porch and I’m unsure if there is a separate DPM and it’s condition. The room in question is interesting as it’s a single skin porch, and the door was wooden and defective so the floor was clearly damp. I am hoping that the damp entered only through the wooden door (now replaced) and maybe the wall in intense rain. Certainly the most damaged blocks fan out from the door. I recognise it’ll be difficult to test for dpm. The black layer is very thin (1mm).

    Question is how can odd blocks be re-fixed to the bitumen? This is after I confirm that their is both dpm in ok condition, and bitumen adhesive. I was looking at F-Ball Styccobond F21 as this is a bitumen based wood floor adhesive or possibly even some kind of bitumen roof mastic…

    Ash.

  • Hi Ash,

    This is one of them question, ‘how far do you go?’.

    If your general thought here is to simply glue back down a couple of square metres of parquet, I see no issue using F21 for said purpose. It would be worth lifting the effected area first to allow any damp areas to dry, while in the mean time preparing the blocks to go back down i.e. removing loose bitumen adhesive from the back.

    Be sure to follow the guidance from F-Ball in relation to applying the F21.

    I hope that’s of some help.

    Regards,

    Wes.

    P.S. I did see your post relating to the same question in the UHM forum, but decided to answer as best I could here.

  • Ashley Martin

    Thanks.

    Sadly the technical reply came back that the adhesive needs an absorbent base to dry so the bitumen would need to be mechanically ground off. In that case it would be following a technical approach similar in approach to your Ian response.

    Ash.

  • Hi Ash,

    Fair enough. I think it was always on the cards that F-Ball would advise that.

    If the area is very small, you could use a basic 4 inch grinder with an extraction hood like this http://amzn.to/2aCX3zV (being sure the hood is compatible with your grinder), a wet and dry vacuum attached, and a cup disc like this http://amzn.to/2aPbvbz. If it’s a larger area, I’m afraid you’ll need something a little more substantial. Ideally a 10 inch stand up grinder or upwards and commercial extraction.

    Please refer to ‘Ian response’ for other basic instruction.

    Regards,

    Wes.

  • Hi Mike,

    I would fully expect the smell to go after removal of the majority of the bitumen, installation, and finish. However, I obviously cannot fully guarantee that, but can say I’ve never heard of any complaints about bitumen smells from reclaimed parquet floors in twenty years.

    Sorry I couldn’t give you a more definitive answer Mike.

    Regards,

    Wes.