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Flooring Installations Are Best Warm & Dry

Martin Cummins on site conditions

AS I visit sites and chat to flooring contractors it is very evident that pressures from main contractors to get jobs done is more and more of a problem these days.
Talking recently to a time served, long in the tooth, nearly ready to retire contractor the nostalgia of the past came through. He told me that professional flooring once had a much stronger standing and was a much more respected trade.
He could arrive on site and if the areas where not ready or there was insufficient lighting then they would simply tell the main contractor to call them when it’s ready, and simply leave site with a day’s pay!
Sadly those days seem to have completely disappeared, with the flooring trade now seemingly prepared to put up with a lot worse on site and try to work around it to help out.
This may sound like a very amenable and helpful approach, but it does present its own problems.
Remember that if you do the work, under the conditions given, then it is very difficult for manufacturers to back your installation as all products have performance limitations.
So what are they key stages and what conditions are required?
l Subfloor preparation: This includes smoothing compounds, primers and surface DPMs. Sites need to be clear of obstruction and surfaces must be dust free. Sticking to dust means the integrity of the floor is reliant on the bond of the dust to the substrate!
Products generally perform by curing and/or drying. The limiting parameter for curing of products is temperature. Epoxy DPMs, rapid set smoothing compound, resin based primers etc. all work far better at 15 to 20degC than at 10degC.
The rates of cure are significantly reduced as temperatures drop. In fact, below 5degC many systems will fail to cure successfully so it is important to get a subfloor temperature of at least 5degC (and rising).
Along with temperature is humidity, or in main contractor terms dampness in the air. If the air is damp (condensation on the windows, raining outside and no windows etc.) then products that are required to dry out to perform cannot dry at anywhere near the rate claimed and some can take days and days.
Humidity can also be high in buildings in summertime, particularly on new build projects where a lot of wet trades are working.
So get heat in the building (not fuel burning space heaters as they add moisture to the air) and also decent ventilation.
Consider using underfloor heating systems to both keep the building and the subfloor warm. Use dehumidifiers, particularly overnight as the air temperature drops and condensation can be more prevalent. So, warm and dry.
Specify your requirements when agreeing the contract, otherwise the main contractor will expect you to get your required conditions and foot the bill. The electricians, plumbers and other trades don’t require the same conditions generally so it isn’t a requirement in the main contractors mind.
l Adhesives and floorcoverings: Manufacturers are moving more and more to solvent free, water based products when it comes to adhesives. Therefore the same issues for subfloor materials also apply to adhesives and floorcoverings.
Humid and/or cold conditions means that adhesives will not give up their water easily so may not develop the required tack and grab. Also, the bond strength build up will be significantly slower.
Historically the use of solvents within adhesives has helped in this respect (solvents can evaporate at a much lower temperatures than water), but things are changing, for the environment, for the manufacturer and the installer’s health and safety. So again warm and dry.
When it comes to floorcoverings the requirements are often prescribed by the manufacturer, and for good reason. Vinyl (PVC) for example has a degree of thermal movement so if laid too cold then it will expand as the building warms, too warm and it can shrink.
The typical temperature requirements are around 18degC which is quite warm for a site. If you are warming up specific rooms to enable vinyl to be installed, ensure you keep the warmth in there for several days after to enable the adhesives to build up the bond strength.
You will not be covered if you simply install in the warm then switch off the heat once you’ve finished fitting.
When it comes to carpets cold and humidity both play a part. Absorption of moisture, particularly in unbacked carpets can cause a ‘relaxation’ in the tension within the roll. When this moisture dries out the carpet can tension up and potentially shrink.
The cold makes carpets, particularly fibre bonded, very ‘boardy’ meaning that they are always trying to curl back.
This, with adhesives being at their weakest performance in the cold, can be very problematic. The possibility to weigh down carpets is very rarely present so you need the conditions to get it right, once again warm and dry.

Timber flooring: When it comes to timber the situation is a lot more obvious. Timber ‘swells’ in the damp and shrinks as it dries. We know this from our shed doors being a pain to open in the winter but barely filling the door frame in the summer (or is this just me…).
It is exactly the same with flooring manufactured from timber. The most problematic is solid timber of large dimensions. Engineered timber can be more forgiving.
Linoleum can have some of the issues of both carpet (stiffness) and timber (moisture affecting the backings) whilst rubber will also have very strong thermal movement.
So, the message has to be, get your conditions right then the products will perform as specified. Failure to do so may result in flooring failures. The key in all cases is warm and dry.
Martin Cummins is UK technical support manager at Bostik. T: 01785 272625

This article has been reproduced from the Contract Flooring Journal. You can find them at