The warmer weather we’ve been having over the last few days has reminded me of the cold conditions we all hit just before Christmas – and the precautions we need to take when using mortar in the colder times of the year. It’s not only winter flu that cries out for a safe cure.
Using mortar in colder conditions needs careful thought and the taking of a few precautions. It all comes down to a simple equation which can be related to daily temperature x number of days. It’s the basis of how mortar cures safely and gains its working strength. Don’t be tempted to think because you’ve left your mortar for three weeks before the frost comes you’ll be safe. If your daily temperature has been lower than, say, 1o or 2oC, the mortar will not have gained its safe working strength. You need at least a temperature of 3oC for a number of days. If the temperature is lower, curing will take proportionately longer.
You can take a few measures to help things on its way when cold snaps are about. Drape sacking or bubble-wrap over the brick or blockwork but if you use sacking, cover it with polythene sheet to avoid saturation. Take special care where there is a north or easterly aspect, especially so if the ground falls away and there are no buildings or trees to provide a windbreak. Also, don’t forget that for every 1000 feet increase in elevation the temperature falls by 2oC, (that’s why the temperature outside your holiday jet is around – 42oC).
And if you have any doubts, consider postponing the work until the weather forecast looks a little more promising – remember, best practice suggests a minimum temperature of 3oC and a rising thermometer.