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Cold weather construction: laying concrete blocks in winter
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Concrete blocks are a popular building material in the UK because they are able to withstand a range of weather conditions, from ice and snow to heavy rain and strong winds. However, we’re often asked if you can build with concrete blocks in the winter. This article explores how to use concrete blocks in cold weather.
Can you lay concrete blocks in winter?
Yes, you can lay concrete blocks during winter, but the conditions must not be too cold. Concrete blocks should not be laid if the temperature is at, or below, 3°C and continuing to drop. This is because mortar will not cure correctly if the temperatures are too low, resulting in weak masonry. Blockwork can resume when the temperature is 1°C and rising with the prospect the temperature will exceed 3°C.
Even if temperatures are above 3°C, it must not be frosty, icy or snowing. Frozen materials must be thawed before use and must not show signs of damage, in order to maintain the structural integrity of your project.
Storing concrete blocks and mortar during winter construction
Concrete blocks and mortar should be protected wherever possible during winter months to prevent moisture ingress and the risk of frost damage. They should be stored in dry, sheltered areas. Blocks should also be raised off the ground on pallets, and protected by covers if inclement weather is anticipated. This prevents the absorption of ground moisture and rain while reducing the risk of freezing.
Mixed mortar has a limited working time of between 90 minutes and two hours, so storage is generally not an option. However, unmixed dry mortar can be stored. It should be kept dry and in an airtight container. For larger projects, the use of dry silo mortars is a good storage option.
Concrete block construction in winter weather conditions
Before you begin
Check the local weather forecast before beginning any masonry work. If cold weather is expected, set up thermometers around the site to monitor temperature drops and take extra precautions if necessary.
Concrete blocks should not be laid on frozen surfaces, so even if the air temperature is suitable, you may need to check the surfaces for signs of frost. Where very severe frosts are expected, heaters may be required.
During cold weather, provision should be made for somewhere warm for workers to shelter from the conditions. It is recommended that walkways are kept clear of ice. Because cold weather usually coincides with shorter days, you should also ensure there is sufficient lighting on site.
During construction
If temperatures drop unexpectedly while on-site, monitor conditions closely and stop work if it becomes too cold. In addition, discard any blocks or mortar showing signs of damage. These may compromise the finish and quality of your project.
If there is a cold wind blowing, consider setting up windbreaks. These will reduce the amount of cold air around your work, helping to maintain the temperature.
After laying blocks, masonry walls should be covered with hessian blankets, frost blankets or waterproof sheeting to retain heat and block moisture. This helps the mortar cure properly, maintaining its strength.
It is important to remember that polyethene sheets must be kept away from the surfaces in case condensation forms. This could make the blockwork and mortar damp, preventing it from setting.
Insulation boards can be used if it is very cold or you could consider using heaters to keep your work warm. This will help the mortar to cure and prevent frost damage.
Air entrainment admixtures can be added to the mortar to improve its resistance to freeze-thaw conditions. Using this technique creates bubbles in the mortar, which means freezing conditions are less likely to cause cracks and weaknesses. However, this will not make the curing process any faster.
Finishing the project
Once construction is complete, inspect the general condition of the blockwork looking for any signs of frost damage. This may indicate that the mortar hasn’t cured properly. If any are spotted, you can implement repairs.
You may notice efflorescence occurs if the blocks aren’t adequately protected. Efflorescence occurs when soluble salts within the concrete or mortar migrate to the surface as moisture evaporates. This will appear like a white tide mark, as some of the minerals leach out of the blocks. Efflorescence is harmless and can usually be removed with a stiff bristled brush.
Find the right block for your next project
If you’re planning a winter construction project, our team is here to help. Whether you need advice on the best concrete blocks for cold weather or guidance on proper storage and installation, we can provide expert recommendations tailored to your needs. Get in touch today to ensure your build stays on track, whatever the weather.
