Plank Separation

Plank separation or gapping in wood floors is very common and can be down to several reasons. This article focusses on how it occurs and some ways to rectify it, if and where possible. 

Excessive moisture

Should a room or property be subject to excessive direct moisture i.e. A leak or spillage etc, this increase can result in the break down of the floor adhesive. You would generally see other damage to the wood like swelling joins or a ripple effect across the floor where the wood has expanded beyond it’s maximum, grounded against solid surfaces and buckled. If moisture breaks down the adhesive, it may be subject to de-bonding. In other words a loss of adhesion to the sub-floor or underside of the wood flooring.

Often, failure of the damp proof membrane (DPM) under a floor can allow moisture to penetrate through to the sub-floor surface which can result in de-bonding. Again, other signs of rising moisture can often be seen i.e. Cupping. This is where the moisture content has risen on the underside of a wood floor and swelled the planks. With the top surface being a lot drier, cupping will often form.


Room humidity

When the air humidity in a home drops, in other words the air becomes drier, a wood floor will shrink. This is generally associated with the colder season’s. In this context, gapping is a very natural occurrence and no action should be taken. You will often see these gaps close up as the air humidity raises going into the warmer months. If your wood floor is installed in the colder months, it is advised to leave adequate expansion gaps throughout the installation. These expansion gaps will allow each plank of a permanently fixed wood floor to breath. Problems associated with  expansion can often be seen in warmer months as adequate expansion hasn’t been left if an installation has been carried out in the cooler months.

Gaps can be a natural feature of your breathing wood floor

It’s worth mentioning that artificially dry climates can also create shrinkage and gapping problems with wood floors. Air conditioning units can play havoc! In summer when the air humidity is high the floor will expand naturally. Introduce an air conditioning unit into the equation and drag that humidity out of the air quickly, and you may be bringing on a rapid climate change that a wood floor will not thank you for, such as cupping. Think of a leaf that has fallen on a wet ground on a sunny day. It will curl up as the sun dries the surface of the leaf out and the underside stays moist for longer.

Should a rooms air humidity raise significantly, the wood will expand as it takes on more moisture. In some cases, due to the  significant increase in air humidity the shear forces that the adhesive are designed for will be pushed to the limit. Where the wood floor may cope with the increase in humidity, the adhesive may not. This is dependent on the quality of the adhesive. As with all products, you get what you pay for. If the adhesive is strong enough to keep grip, you may often see compression lipping of the wood floor.

One of the main reasons for plank separation is a poor bond to the sub-floor. If the adhesive has not been applied or the sub-floor not prepared correctly, de-bonding of the adhesive will often happen, resulting in plank separation.

Here we can see a classic example of plank separation. There are no signs of swelling or moisture damage, hence we can assume this is a result of the adhesive de-bonding or locking system failure if it were a glue free overlay floor covering.

We actually found that this was due to a small leak from a  radiator pipe. The water had ran down the pipe and under the floor. Just goes to show that moisture damage isn’t always obvious to spot. The leak had broken down the fixing adhesive and the bond lost it’s strength.

Another sign of de-bonding is a hollow sound to the floor. You should be able to tell the difference between a bonded and de-bonded section by tapping the floor. A hollow sound is much louder and has a greater resonances as air pockets will form once the adhesive has de-bonded and vibrations will travel further. A fully bonded floor will absorb the tapping, giving a far more quite and solid sound.

With a directly bonded engineered or solid floor, once plank separation has occurred, it is rare that a repair to an adequate standard without removing the floor is possible. Adhesive injection is sometimes used but the success of such a method is very much dependant on the reason for plank separation. Fillers can be used in the exposed gap but this is a cosmetic covering and again will not solve the issue itself. Fillers, over time, will often work loose with cleaning and use.

Floating floor plank separation

I have mainly discussed plank separation for solid wood and engineered floors that have been directly bonded to the sub-floor. However, plank separation can also occur with floating floors.

With a floating floor, the rules of expansion due to air moisture still apply. However, we are not dealing with adhesives due to the nature of the installation. Many of today’s floating floors have a built in glue free click system used as the method to join the planks together. This means they’re not bonded to the sub-floor in any way.

If room air humidity increases greatly, as with a direct bonded floor above, the floating floor will expand. If the expansion exceeds the limits of the locking system, a rupturing of the locking system can occur. Once the locking system has ruptured, the planks are free to separate and will do so during the life of the floor. Again, you would generally see other signs of moisture damage should a raise in air humidity push the floor to expand to such an extent.

Another reason for plank separation is a poorly fitted floor. If the sub-floor has not been prepared correctly and there is excessive movement of the floor when walked on, this can cause abrasion of the locking mechanism, eventually resulting in plank separation.

In some cases, damaged or miss machined locking systems can be the cause. A full inspection of each plank should always be carried out prior to fitting to avoid this.

Planks that have separated on the end join of a floating floor, can often be fixed, although in some cases this can be difficult. Applying PVA adhesive in the gap and knocking that particular row of planks together can solve this issue to good effect. However, if the separation is due to any other reason than a ruptured locking system, the original problem may re-appear in another areas.

If the main length of the locking system has separated it is often possible and required to lift the floor and replace the relevant rows, or live with it.

The may problem with leaving the area obviously being cleaning and general day to day use. A separated plank or the ensuing gap is a grime and dirt collector. If the only choice you have is to leave the floor until you’re next ready to approach the issue, I would strongly advise the gap to be filled with some form of flexible sealant. This may not look the most attractive, but the sealant will go a long way to preventing moisture from cleaning seeping through, damaging and/or stagnating underneath your floor.

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

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,,,,,,, affiliate window network.” This statement is to comply with current internet regulations regarding transparency to consumers.

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