MPA Mortar part of the Mineral Products Association (MPA)

mpa mortar

quality factory-produced
mortar since 1971



June 2024

On-site Hot Weather working with Mortar

With our summer promising very hot temperatures we need to ensure both those working on site and the mortar and associated materials being used are carefully looked after.

Mortar Heat

Firstly, those working on sites:

  • Introduce flexible hours, avoiding where possible working in the hottest parts of the day
  • Ensure everyone applies sun cream (at least SPF 15) regularly during the day and probably at least every two hours
  • Remind everyone they should wear lightweight, long-sleeved tops
  • Ensure regular breaks are taken out of the sun
  • Provide and make sure workers consume plenty of fresh water - more than 2 litres of water a day per person
  • Encourage the removal of personal protective equipment when resting to help encourage heat loss
  • Educate workers to recognise early symptoms of heat stress dizziness, head aches, hot dry skin - and to look out for each other.

Secondly, the mortar:

  • Evaporation of water from the mortar is the greatest potential problem. If sufficient water is not present, the bond between the mortar and masonry unit may be reduced. However, the increased rate of hydration of the cement and favourable curing conditions in warm, humid weather will help develop masonry strength if sufficient water is present at the time of construction.
  • Storing bricks and blocks in the shade or under cover will help control heat gain as warmer bricks and blocks will generally absorb more water from the mortar.
  • Reducing the suction rate of bricks and blocks by spraying or docking with potable water may be necessary in extremely hot and drying conditions, but care should be taken to avoid excessive wetting.
  • For further information on using mortar in hot weather go to MPA Mortar Data Sheet 07 - Factory produced mortar for use at low and high temperatures.pdf.


If you would like to be added to the electronic Mortar News mailing list, please email your details to Mick Russell.

MPA Mortar Office

c/o Mineral Products Association,
1st Floor,
297 Euston Road,
London, NW1 3AD

Tel: +44 (0) 20 7963 8000
Fax: +44 (0) 20 7963 8001

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