Gary Haigh, ARDEX group UK training and technical manager (North East), offers some best practice advice for working during the hotter Summer months
Extremes in weather caused by climate change is leading to hotter temperatures in the Summer – with 2022’s record highs of 40° + looking set to become more frequent.
Extreme temperatures – whether this is heat 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 adhesive 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.
The reverse is true at colder temperatures which can see working and open times increase significantly.
While we can use specialist additives in cementitious tile adhesive formulations to control the chemical reaction under ambient temperatures i.e. 20°C for rapid-setting cementitious tile adhesives, the rate of stiffening and hardening of the mixed mortar increases significantly. This means much shorter working and application times.
Hotter or cooler temperatures will always create issues which tile fixers need to be aware of.
To compensate for higher temperatures, use of 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 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 3-4 kg 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 standard setting tile adhesive.
The UK market has seen the launch of many of these “semi-rapid setting” products.
Whilst longer open and working time performance will always be achieved more consistently using a standard setting adhesive, dependent upon the site temperatures, a product using a semi-rapid cement chemistry as a basis may also prove to be beneficial.
When working externally, you also need to consider the use of additional movement joints and should be incorporated every three metres, instead of the traditional 10 metres. For further information, or advice when tiling in the heat contact our technical team today.
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