Use glue and you won’t come unstuck

TO float or not to float, that is the question. But what is the answer. I get asked this question on many occasions. My personal preference is gluing. However because I prefer gluing doesn’t mean it’s the only method.

Let’s break down floating and full-bond systems and see their advantages and disadvantages.

Advantages: No messy installation; possibly quicker and obviously no adhesive to use.

Disadvantages: Underfoot movement may cause complaints from consumers; not the best method for underfloor heating (I await calls from underlay manufacturers); breaks required between rooms in doorways; provision for expansion is critical; if you use a non locking system there is the potential for adhesive bond breakdown on joints if there is any underfoot movement; when the floor requires future sanding the chance is high that sanding will create bounce, causing waves in the flooring.

Disadvantages: Incorrect trowel; Can be messy if not careful and possibly takes longer to install.
Advantages: Can be sanded easily with no bounce; gives a much better under foot comfort and acoustics; you can install much larger areas without being concerned with breaks in doorways; it is much better on underfloor heating; has a system superior tog rating; and gives a more secure installation.
The most important factor in both systems is correct subfloor flatness. In other words the subfloor must be flat, especially with 21mm multi ply engineered boards. It amazes how many installers think that because the product is 21mm no subfloor preparation is needed.

With many complaints I attend involving floating floors the problem is due to excessive underfoot movement – such as when the consumer has to hammer 6 inch nails into the Welsh dresser so it will not fall over when anyone walks over the wood flooring.

I can’t tell you how many times I have been on-site with the installer tells me: ‘I thought this stuff could bridge any rubbish subfloor’.

No it can’t! The other issue I often get when I am called out is because the product has shrunk by 5mm at joints, or so they think. I then measure the product to find it is perfectly in dimension.
The actual problem, more often than not, was that the installer applied the PVA incorrectly. In fact, it is seldom done correctly. What happens is that over time because of excess movement or incorrect application the bond breaks down between the boards. They then open up due to the cumulative movement of the rest of the floor. Because the bond has been broken the boards will inevitably part company.
On the full bond method things that can go wrong are subfloors not being flat or clean and an incorrect trowel having been used. Sometimes a vinyl trowel is used and, of course, it will go wrong.
I hate manufacturers who sell trowels with hardly any notch, so they can say their adhesive has a better spread rate than their competitors. If it goes wrong you know exactly what they will say? The subfloor was not spirit level flat or the wood flooring is to blame or something else, so please be sensible and chose the correct trowel.

If it says the spread rate is 20sq m then think more like 16sq m. Then you will be getting something like the correct coverage. Other than those issues, if all is done as it should be then gluing full-bond is without doubt a far superior method by a mile.
Our European cousins can’t believe that we float engineered floors most of time. They say, like me, that there is no real comparison with full bond; it is so much more superior. So why isn’t it done more widely in the UK? Perhaps there are a number of reasons. Price is probably the main one, with failure or fear of failure the second reason.

When ever I chat to retailersorcontractors and ask why they don’t do full-bond floors, the most common answer is that customers will not pay. This one always annoys me because they think they are talking on behalf of the consumer and deciding what they may say or not. If you explained to most people the advantages of full- bond I guarantee that, in the majority of cases, full-bond would be their choice. OK I know what some are thinking – what if something goes wrong, like a possibly faulty product? If the product is faulty – although this possibility is unlikely – the supplier will have to pay for work to uplift and prepare the subfloor again.

Remember when you as a professional install a floor it is your responsibility to check for any faulty planks, etc. And if any are discovered, then don’t install them.
Now when I say full-bond, I mean full-bond, not blobs of adhesive every 30cm. I am not a fan of the sausage application for many reasons: If the application is too thick and too far apart, the floor will have bounce between the glue.

The other reason is that most of the time, especially if shorts are a problem, you will inevitably not get any adhesive on headers, causing you issues later on. I am happy to use the sausage to finish the last or first planks or in combination with nailing, if of course the product is suitable for nailing. I have seen too many complaints using this method on solid wood and engineered.
As usual I may have upset some manufacturers of the sausage, but I can only tell it how it is. I find it silly sometimes when you see people doing a great job selling their product but have no idea about installing wood floors. Some may have been on a courses (for which I applaud them), but you cannot beat real life experiences and what you learn from them on what will be successful and others that may cause problems later on.

The other system I don’t oppose for installing engineered flooring (except on under floor heating) is the self-adhesive underlayment like Elastilon, and not the imitations of this product. However do treat it like a floating floor for expansionanddoorways.

Sid Bourne is an independent consultant. He does inspections, NVQ assessments and on-site training.