Posted by Martin Cummins on

How heat and humidity impact you and your products

Martin Cummins

Published by Martin Cummins - UK Technical Support Manager, Bostik

Martin has been involved in the industry for over 20 years. He’s passionate about flooring in all its guises, with his particular expertise being in subfloor preparation products and adhesives. Martin is an active member of the CFA manufacturers committee and he sits on the CFA council. He aims to keep abreast of all the changes in the industry and feeds this knowledge back to installers to make sure when floors are laid they perform to their maximum potential.

I’m writing this fully confident summer is on its way, so I’d like to briefly discuss what the impact of hot and sometimes humid conditions can mean to flooring contractors and also to flooring products themselves.

The first thing I’d like to point out is that product storage can make a massive impact on performance. We talk in the winter of products needing to be at room temperature to give optimum performance.

In technical terms, when we say room temperature, what we’re really saying is typically 20-23deg C. Adhesives, primers, DPMs, smoothing compounds etc all have stated curing and drying times based on this sort of temperature (as well as 65%RH air humidity) with a general understanding that colder or more damp environments can slow these parameters down.

You can, of course, warm the materials and the building up to these optimum conditions, and much has been written about how best to do this.

When it comes to temperatures heading in the other direction, the situation isn’t so straightforward. The reference to higher temperatures is in relation to the product itself, from perhaps storage in the back of a very warm van or lorry, or storage in a lock up, and also to their use on a warm site.

I’ll start by looking at epoxy DPM systems, as these are most often the first products used on a project. As two component products, they’re designed to be mixed together and applied to the floor while still in a fluid state. This enables them to ‘wet’ out onto the floor, and to be easily trowelled or rollered with a good flow, which allows the critical formation of an even film.

As soon as the two parts are mixed up they’re beginning to cure. If the products themselves are already warm (25deg C and upwards) then this reaction rate is increased. The higher the temperature, the faster the products react and thicken up in the bucket. This then makes it harder to trowel out owing to reduced flow and subsequently jeopardises achieving that controlled film.

Using a large size unit of product in particular may in fact end up with much of the product having gone past the point where it’s able to be applied effectively. If you have product onsite, find the coolest area to store it, out of the view of windows and sunlight. Should you find yourself having real difficulties, place the products (still in the containers) in cold water in an available vessel.

Obviously don’t allow the water over the lids in case it seeps in.

When it comes to moisture suppressants, we’re generally talking about water-based products that perform by drying out, not reacting. When water-based products warm up significantly, their viscosity can greatly reduce. In layman’s terms, this means they become more ‘runny’.

The difficulty with moisture suppressants is they should be applied to give a certain film thickness, which is very low in microns. When the product becomes lower in viscosity it becomes much easier to spread out. The danger here is that you’ll over-extend the product and not give the required moisture protection across the floor.

Always mark out the area and calculate beforehand how far one unit should go, or how much you need for the given area. Also, it will start to dry out much more quickly in the warmth, especially when it’s a low humidity heat, so you need to ensure you don’t ‘drag’ the product back off the floor during application. The solution is exactly as for epoxy DPMs – store it in the cool or cool it down before use.

Primers are generally water-based and can be considered as low-viscosity products. The issue therefore mirrors that of moisture suppressants to some degree, although the criticality is not so great. When using as a barrier primer, however, it’s extremely important to control your coverage rate to give the desired effective barrier, eg for cement onto calcium sulphate screeds. Again, the solution is as above.

The smoothing compound application is normally next. The issues here are a combination of two things as a result of the mixed product reacting too quickly. First, the application characteristics will potentially be greatly affected.

Cement reacting quicker will thicken up the product, reduce its trowelability and make it much more difficult to get an even finish. Spiked rollers can make an imprint rather than smooth out ridges owing to the product ‘gelling’ up much more quickly. The rapid setting products in the market today may well suffer more significantly as they have such a short pot-life that they’re virtually impossible to lay if doing more than a couple of units.

Pumping of products brings its own issues in terms of keeping water feeds cold as well as the bags of powder themselves, particularly when working from outside. I always advise to try to set up the pump on the side of the building which will be mostly in the shade while pumping.

Second, if the product reaction rate is increased significantly then it may well shrink and crack on the substrate, and in severe cases uplift from the floor. Dehydration of moisture from the surface owing to low humidity or a ‘cooling’ breeze can well be an issue too, causing hairline crazing.

I’m not going to suggest you put the bags into cold water to cool, but you can do that with the liquid components. Storage of powder at as low a temperature as possible is advised. The powder holds heat very effectively, so out of sunlight in as dark a corner of your warehouse or the site is the best recommendation.

Finally, the laying of the floorcoverings. Some of these are going to be very flexible and easy to work with in higher temperatures, but as they cool down, they can shrink and put unexpected strain on the glue line. Keep the vinyls and rubbers as cool as possible before even considering installation.

The adhesives themselves will have similar application issues as they become warmer. If they become too runny, they won’t fill the ‘v’ notch on your trowel meaning there won’t be enough applied onto the floor. Insufficient adhesive is a sure way of getting floorcoverings to fail to stay bonded. Much testing between adhesive and floorcoverings takes place and coverage rates are always found to be key.

A further issue with adhesives is the available open time. The water from water-based adhesives (most products in the market are now water-based) will evaporate more quickly resulting in a much earlier grab (occasionally a benefit), but also an early onset of cure/setting. An adhesive that isn’t laid into during its acceptable working time may well fail to hold the floorcovering. Working times are quoted at room temperatures and once we climb above these the open and working time comes down rapidly. Working in smaller areas is one way to minimise these issues but the best answer again is to get optimal storage conditions.

The main culprit is storing products in the back of a van at night – there’s little air movement and the products will have heated up the previous day. As they cool down at night they can sweat in the small areas they’re enclosed in. This can cause cements to dampen and harden, adhesives to have a watery film on them and, with some ‘latex’ liquids, can affect the performance of the biocide within them, resulting in a smelly liquid.

As much as we love the hot weather, do heed the problems it can create and do all you can to limit these issues.