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-   -   is it bad to do masonry work in (near) freezing temps? (

amakarevic 12-21-2010 11:09 AM

is it bad to do masonry work in (near) freezing temps?
because the fresh concrete/mortar can freeze instead of dry ?

i laid some bricks yesterday building a small wall between me and the neighbors and luckily the temps didn't go below freezing but in the days to come they will so i was wondering if i should leave the rest of work for non-freezing days.


Daniel Holzman 12-21-2010 12:10 PM

First off, a bit of terminology. Your are probably using mortar to hold the bricks together, not concrete. Mortar is a mix of sand, water, and either lime or portland cement. Concrete includes aggregate. The procedures for working with mortar in freezing temperatures are different than concrete.

Neither mortar nor concrete dry, they cure. Curing is a chemical process of conversion of the cement into a different chemical by absorption of water. Curing generates heat, so if you insulate properly, you can prevent the free water in the mix from freezing. At least with concrete, it is possible to place concrete in temperatures well below zero F by using the proper mix, insulating the forms, and in extreme cases adding heat.

Mortar is a bit trickier, as it generates less heat because you use only a small amount of mortar per brick. At least in Massachusetts, placement of brick or block when the temperature falls below 40 degrees F requires special mortar mix, and special procedures. Personally, I would not use mortar below 40 degrees F unless it is critical, and then I would consult with a mason about proper procedure.

amakarevic 12-21-2010 01:10 PM

thanks. what's a good way to insulate ?

stuart45 12-21-2010 01:22 PM

We usually cover with hessian sacking and boards over the top after work.
If possible it's best to avoid laying bricks in cold. Mortar can still be affected days later.

concretemasonry 12-21-2010 02:24 PM

From a durability or ultimate strength standpoint, mortar can freeze if it is not saturated and the cured masonry absorb the excess moisture, which only takes a few hours if you use warm mixing water and the sand is warm. The ultimate strength of the mortar will usually be obtained and is really not a big factor in the compressive strength of the wall.

The concept of covering the surface of the walls in cool weather (per the Cold Weather Masonry Construction Standards) is for protection of the surface appearance and prevent freezing of joints when some moisture is drawn to the surface while tooling late in the wall construction.


amakarevic 12-21-2010 02:37 PM

Dick - are you saying that it's OK to lay bricks if the air does not drop below freezing withing a few hours? so if it's 40 during that day and it doesn't hit 32 until 6 hrs after i laid them, will i be fine ?

stuart45 12-22-2010 06:52 AM

If you get a severe frost and don't cover it, you might find the joints go a bit flakey and the face crumbles off. It then needs re pointing.

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