David Wilson, UK head of standards and specification at ARDEX UK and BAL, explains some of the challenges associated with tiling in extreme temperatures and how you can overcome them
This year we saw record temperatures smashed across the UK, with 40.2°C recorded in Heathrow in July.
The heat and humidity continued throughout the summer, with July being the driest in England since 1935 according to the Met Office. These extremes are expected to get worse as the effects of climate change continue to be felt.
Extreme temperatures – whether hot or cold – can cause issues when tiling, particularly with working and open times for tile adhesives.
British Standard 5385 Part 4 states no tiling should be carried out onto backgrounds having temperatures exceeding 40°C. Ideally, at the time of tiling the temperature of the background should preferably lie between 5°C and 25°C – anything above or below these temperatures is going to cause performance issues. Therefore, for backgrounds with a surface temperature over 25°C, the use of a tile adhesives with an extended open time would be beneficial.
When cementitious tile adhesives are mixed with water, they go through a chemical reaction called hydration which generates heat (exothermic process). If the adhesive is applied at higher site temperatures, the speed of the chemical reaction increases. This leads to shorter working and setting times.
Hotter or cooler temperatures will always create issues which tile fixers need to be aware of.
To compensate for higher temperatures, use of a normal or standard setting adhesive, particularly one with an extended open time would be advantageous within the temperature guidelines advised in BS 5385-4: 2015.
However even then, you should still be conscious when tiling in the heat – whether this is externally or internally – or locations such as conservatories, especially South facing ones which will both gain and retain heat for longer periods of time
A change in working practices would need to be considered in order to cope with the extreme heat, for example decisions such as working during early morning or later at night especially during summer months.
Fixers should also consider the following:
- Correct storage of materials. Do not leave bags of cement in direct sunlight or on hot surfaces – even bags left in hot vans can be affected and cause performance issues
- Always use fresh, clean (potable) cold water – leave the tap to run cold before mixing
- If working outdoors, provide a shaded area to work underneath
- Work in well ventilated areas
Mix smaller quantities of adhesive, typically, i.e., about 3-4kg at a time. The more adhesive you mix, the hotter the mix will become and the faster it will set. Traditional rapid-set chemistry uses additives to achieve the balance between improved working times with a faster setting time.
However, there is a limit as to how much the cement chemistry can be altered before strength development and ultimately adhesive performance is adversely affected.
To overcome issues with rapid-sets in hot weather, while assisting in achieving faster project completion, another solution is to consider a -semi-rapid setting tile adhesive – with improved setting times, compared to traditional normal setting tile adhesive.
The UK market has seen the launch of many of these semi-rapid setting products.
While longer open and working time performance will always be achieved more consistently using a normal setting adhesive, dependent upon the site temperatures, a product using a semi-rapid cement chemistry as a basis may also prove to be beneficial.
For further information, you can download BAL’s Tiling in Cold Temperatures and Tiling in Warmer Weather Technical Notes.