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As the long-awaited summer is now well and truly upon us here in the UK, many will be thinking of BBQs, and socialising with friends and family outdoors, but the soaring temperatures come with several issues for those working in construction. The sun’s harmful rays and hot working conditions can have serious impacts on both worker’s health and the products and materials being used on site. 

An area of concern can be that products may dry out before setting due to high temperatures and low humidity. Our Training Services Manager, Chris Lee, discusses his top tips on how to get the best out of Knauf finishing products in these conditions, while staying safe and well in the hot weather. 

Knauf chemical setting compounds (Fill & Finish 30/60 Premium, Joint Filler Premium) need water to set hard, but if the water compound is lost or reduced before setting, for example, the compound has dried before it sets, the chemical setting process cannot happen, which affects the strength and adhesion.  

When using Knauf air-drying compounds (Joint Cement Premium), mixing to the correct ratio’s is always essential, but if the product is mixed too thinly due to the hot weather absorbing the water, there is a higher risk of joint failure.  

  To avoid products drying out before setting, Knauf recommends the following: 

  1. Do not mix more product than you will use in the available time. Factor in that you may be working slower due to the heat.   
  2. Use a minimum of 1mm compound behind joint tape. To slow evaporation, you can also coat the finished side of the tape with a thin layer of compound. This works especially well when using Knauf paper joint tape.   
  3. Remember that areas where insulation has not been placed in the ceiling, such as garages, the plasterboard will be hotter which will result in the compound drying faster. Always plaster any ceiling joints located under the roof as early in the day as possible whilst the temperatures are not as warm.
  4. Ensure the compound is being applied at the right thickness when applying joint compound by machine.   
  5. Don’t try to apply additional coats if shrinkage occurs due to hot weather, as this can mean the tape will become visible. 

When using Knauf Airless Finish, work in well ventilated areas and reduce the area applied prior to levelling as the product will dry quicker on both coats (1st and 2nd) in warmer air temperatures. Don’t be tempted to add any water to the product, and don’t add any additives to slow drying! Always store the bags in dry, cool conditions, away from direct sunlight.  

More importantly is the well being of all workers on site. Remember to take care of yourselves and others by ensuring you: 

    Protect – Regularly apply a high SPF sunscreen to protect your skin from harmful sun rays and painful sunburn. 

    Hydrate – Keep drinking plenty of water. 

    Rest – Take frequent breaks in a cooler shady area where possible. 

For further information on working in hot weather, please visit the HSE website:  

For more information on the Knauf finishing products please contact our Technical Team at: [email protected] 


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