Got fine hairline cracks in surface of your engineered wood floor?


The process of creating engineered wood flooring is designed to create the optimum performance in stability of a real wood floor, compared to the traditional solid floors. Even with this advancement in the manufacturing of wood floors in the last 20 years, the timber is still a real natural product that is hygroscopic, meaning that when it absorbs moisture it expands and when it releases moisture it shrinks. This creates pressure on the boards and can cause the small hairline cracks to appear at their weakest point

These hairline cracks are often not even visible unless you look very closely or in certain lights and angles. The very beauty of a natural hardwood engineered floor, is that it is a living product and will respond to its environment over time. The key thing is to get a good understanding of what to expect and how to manage and maintain the product over time to get the optimal performance and lifespan out of the timber flooring.

If it occurs does this mean the product is defective?

Small hairline cracks are do not necessarily point to a defective product, but a natural occurrence of that wood responding to changes in temperature and humidity. This is shown in the fact, these will close up more as the humidity increases and open up when there is humid times of the year. This can be so subtle you may not even notice it when you are living or working in the building. The hairline crack will always follow a grain line as this is where the tension in the wood is released with the changes in temperature and humidity. Depending on the way the wood lamella layer has been cut out of the tree, if the grain is more quarter cut pattern, it could be more of a straight-ish hairline crack, whereas if it is more of a crown cut pattern, at the top of the crown, where the crack has followed the grain line, this could cause a small piece of the oak top layer to splinter off.

Will they show before or after install?

Sometimes this may show on the planks prior to install but is also likely to show up in the weeks or months following install as the timber adjusts to the environment. Note, this doesn’t necessarily point to a ‘faulty’ product but is most likely the natural occurrence of the wood shrinking and the tension near the heart wood releasing showing in the form of small hairline cracks. Packs should always be acclimatised on site first to allow for the product to adapt to the local and site conditions and give it the best chance of a good outcome during and post install. It is a very good idea to leave the floor for a year to see how it reacts over time before deciding whether any wax repair or replacement is required.

Where they are likely to appear?

Mostly in the heartwood of the tree and where there is more knots and movement in the grain e.g. Rustic Grade planks which often come from the centre of the log are more susceptible to it than a Prime or Select Grade. As it is a natural occurrence there is no way of telling exactly where and how many will occur. It quite often occurs where the heartwood and sapwood meet.

Will it be more obvious on some products than others?

Yes, different textures will affect how visible these little hairline cracks can be. A smooth sanded finish for example is going to make it more obvious than a plank that has deep brushing or sawn marks in it.

Heat & Humidity:

As the floor responds to environmental conditions around it, it will expand and contract. The engineered construction minimises this a lot compared to a traditional solid hardwood floor, but it will never eliminate it. Correct acclimatisation on site, following the correct install methods, especially where there is underfloor heating and/or a lot of large windows, making sure the rooms a kept well ventilated and avoiding. Underfloor heating shouldn’t exceed 27 deg C as if it does this could start compromising the performance of the floor and make it more susceptible to cracks opening up. Hardwood likes to sit as close to 50% as you can get it. It has an “allowable” range of 40% – 60% (roughly) but the 50% – 55% is ideal. 

Is the surface finish compromised?

If you have an oiled finish, the oil is in the timber itself, so there is little or no risk associated with having a hairline crack in the surface. All floors need to have the correct care and maintenance regime on them and for oiled floors this includes applying a Liquidwax Care product which helps keep the surface protected and not ‘drying out’. A wax repair kit can also be used on oiled or lacquered floors and this will help protect the surface of the timber especially on a lacquered floor, as a lacquer is a surface finish, compared to an oil that penetrates into the wood. 

Is there anyway of avoiding this?

The risk of it can occurring as mentioned is more likely in the lower – more knotty grades of wood, so selecting a higher grade will decrease the chance of this happening. Keeping the floor well maintained and the areas it is in well ventilated will all help decrease the chance of it occurring. 

If there was a more sizable crack open up or a small piece comes loose, what are the options to remedy it?

For very small crack, you can either leave it there to close and open over time or use a Wax Repair Kit to fill the crack. As mentioned above, it is a good idea to give the floor a full year before looking at remedial options because if you put the wax repair products in when it is opened up, that could cause the wax to come loose when the plank takes on moisture again and swells. If there has been a major crack open up, a plank may need to be replaced. This should be done by a trained professional.

Please get in touch with our technical team if you have any further questions, we would be glad to help. 

Get in touch if you have any further questions!

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