The 18 x 120mm Solid Floor question
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Feedback received from (professional) floor fitters on Wood You Like's Wooden Floor Installation Manual

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Hi Karin & Ton

Well done on the ‘Installation Manual’, very informative and to the point.

Most manuals are very general and vague about the details, which are the most important bits if you’re going to be able to understand the reasons for doing or not doing certain things. It’s always essential to understand why you’re doing something so that you know why it’s correct and therefore you can then apply that method of thinking in general.

With regards to my flooring project(s). I had just completed a 55 sq.mt area in a new extension for a client before receiving the manual.

The back of the house had been knocked through and the extension was built across the whole width of the house. One third was the kitchen,

which was tiled floor with electric underfloor heating, the rest was covered with 15mm Engineered Oak. The widths were over 100mm and the lengths were all the same, except in each pack were two half lengths just to add some effect. I decided to lay the whole floor ‘floating’ as there were two different substrates. I’ve always been happier floating than gluing or nailing as I feel it’s always best to allow wood to move without restriction. The original part of the house was solid wood floorboards and the new part was screed.

After checking with the builders for method and depth of screed, it was left to dry for at least 6 months before laying floor. The only concern I had was obviously laying the wood across two different substrates without a break (clients choice). I therefore asked around and viewed different forums, to try and find out what methods were acceptable. As you and everyone else are probably aware, when it comes to wood flooring, everyone has a different opinion and no one is completely right or wrong!

The other concern was that the flooring had just come off the boat from China and after leaving the packs to climatise for a week or so, on opening the tie strap on a couple of packs the boards sprung up in the middle! Not wanting to wait another few weeks for replacements, I used these boards over the slight ridge where the new met the old part of the house and spread them out with the good flat boards to keep them down and there was no problem.

As far as the two substrates were concerned, I used the green heavy rubber based Timbermate underlay all over. On the wooden floorboards part of the house I used the version without the vapour barrier, to allow the floor to breathe and then used the silver backed vapour barrier type on the screeded part and sealed the joints with vapour tape. I’m the sort of person who reads the instructions that come with products which not many people do, just in case something has changed or been updated. I mention this because with the silver vapour barrier underlay, it would seem obvious to lay it silver side down, but on reading the instructions it says the opposite? After phoning the technical number they amazingly advised against the instructions, confirming my point! I then double checked with the supplier Topps tiles and because their staff are well trained, they explained it should be silver side up, even though the moisture from the floor would seemingly soak into the green part of the underlay? (*1)

On reading your manual afterwards, I noticed you recommend gluing ply down over the whole area to achieve a common substrate to balance the effect the two different substrates may have on the finish floor. Unfortunately, I only screwed down 6mm ply over the old floorboards to even the floor out and the builders then laid the screed to meet the same level. Hopefully, the decent vapour barrier underlay will keep the floor from being ruined.

I noticed that these engineered boards seem to be extremely stable though. I had left the off-cuts outside in the rain, snow, sun for a few weeks and on returning to the site for something else, I picked up one of the pieces and measured it and even though it was completely soaked, it hadn’t changed size at all, not even a millimetre!

The only other point I would mention was that although the screed was within the tolerance levels, there were pockets of depression which have made the floor slightly spongey under foot, the usual problem with floating floors I know, but it doesn’t impress the clients. The builders made a point of saying there would be no need to lay any levelling compound as they assured the client it was level. Obviously, it can be difficult to even out a floor perfectly, even with levelling compound and shoving bits of underlay underneath as you lay the floor can also just shift the problem along, (as you point out in the manual as well).

So, I would recommend really paying attention to this part of the process when assessing the substrates for flatness as it can make or break the finished effect. The floor looks great and the finishing off, which can take longer than laying the floor itself, makes all the difference, but if when you walk on the floor, it bounces up and down, then the whole finish loses its appeal. After all, clients don’t care about the work that goes into anything, they just want the finished effect.

I would say the manual has been a good read and does answer a lot of questions but, there are always different variables on each job and some tips just won’t work and also some tips seem unacceptable. One that stands out is where you mention pinning flat beading to the floor, which will then move with the floor as it expands and contracts, meaning you would then have to remove the beading and pin it again to close the gap between floor and skirting during different seasons? Unless I’ve understood this wrong, this would not be something any client would want to have done. (*2)

Thanks again for all the good advice,

Tiran

Further explanations of the two issues:

1. The DPM up or down is a frequently re-appearing issue and strange that Timbermate's Technical Support contradicts their own instructions! There is a logic in having the DPM up instead of in contact with the underfloor. It is supposed to prevent (residue) moisture coming in contact with the wood and some manufacturers follow the thought that a sharp or rough underfloor surface could damage this protecting layer, rendering its function obsolete and therefore instruct to have the DPM upwards where it cannot be damaged so easily and protect the wood.

It is good to read that you always read the instructions, because as you say, they can change once in a while even when the product itself does not seem to have changed.

2. As for the beading moving with the wooden floor - that's correct, but.... it comes down to informing the client upfront about this. Most of the wooden floors now are wood-engineered and as you have experienced yourself with the off-cuts, this type of wooden floor hardly moves.
With solid floors it is another matter - where it can even be considered an "early warning system" that there is (normal seasonal) movement of the floor going on. And yes, clients of ours who do opt for solid wooden floors do call us back sometimes (hence our 4-seasons guarantee on labour) but most know what is happening and fix it back themselves while checking their house climate better.
All in all our clients prefer this unobtrusive cover of the expansion gaps over the standard scotias or quandrants.

Kind Regards and thank you for your feedback
Wood You Like Ltd
Karin Hermans / Ton Slooven

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