At what temp does brick mortar require an additive?

threeapplesNovember 4, 2012

Our house should be all bricked by now, but we had a series of issues with the masons and, as a result, we've been without masons for many weeks now. We have quite a bit left that needs brick and, now that the temps are in the low 40's, I fear our mortar will need an additive. What temperature requires this? I'm hoping we don't need to use it since I hear it weakens the mortar, but we may have to. I also hope the new masons lay the brick well and we don't have one half our house looking like it was done with a new crew, though that's a whole other issue. thanks.

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Cold weather brickwork is not as simple as adding and additive.

When the ambient temperature falls below 40 degees F, the water requirement to reach a given consistency is reduced, an air-entraining agent is added and final set of the mortar is significantly delayed so strength gain rates are reduced and tooling and setting times are delayed reducing the number of courses that can be laid in a day.

Accelerators are sometimes mistakenly thought of as "antifreeze" admixtures. Their function is not to reduce the freezing point of mortar, but to increase the rate of strength development. Calcium chloride is commonly used in concrete but it can cause corrosion of imbedded steel ties in brickwork so other accelerators may be preferred.

All masonry materials should be protected from rain, snow, ice and moisture from the ground.

Below 40 degrees masonry materials may need to be heated to assure full hydration and the work might need to be covered and heated.

    Bookmark   November 4, 2012 at 7:45PM
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Tent it and heat it ($$) or wait until spring for the rest.

    Bookmark   November 4, 2012 at 11:02PM
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At what temperature should we consider renting and heating it? Not sure I want half of the front of my house unbricked all winter

    Bookmark   November 5, 2012 at 9:27AM
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Sophie Wheeler

The brick isn't the waterproofing for any home. It's the drainage plane behind the brick. Your home won't be any less weather tight for not being covered with the exterior cladding. And you're already talking temperatures where you need to start heating the brick and the space it's being installed onto. Heating the install zone and not heating the bricks too is a waste of money.

    Bookmark   November 5, 2012 at 9:43AM
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No solution just wanted to say I am sorry! I know how stressful a build can be in general, and this would have put me over the top :(. Hopefully someone comes up with a satisfactory solution.

When are you supposed to move in?

    Bookmark   November 5, 2012 at 10:00AM
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Athens, yes, I'm very annoyed!
Can anyone just let me know what temp adfitive is required? Is laying brick in 40 degree temp a bad idea?

    Bookmark   November 5, 2012 at 10:21AM
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Using an additive to increase the strength has less than satisfactory results. That is why you are getting the suggestions to increase the temperature of the product and the install site. That IS what actually works to keep the project going.

    Bookmark   November 5, 2012 at 10:27AM
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My masons finished up a fairly large brick job in Northeast Ohio on Saturday,laying approximately 800 brick. They used propane heaters to heat the brick as well as to help dry out mortar joints for striking. Anything more than this amount of brick and we would have been tenting in the un-bricked areas to heat the brick before and the wall
after installation. I won't use an accelerant on just a portion of the job. Since it sounds like you already have a lot of brick installed, I would be tenting and heating at this point. To strictly answer your question, we use an accelerant on new jobs if the night time temperatures have a reasonable chance of dipping below freezing at any point during the job.

    Bookmark   November 5, 2012 at 10:55AM
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The Portland Cement Assoc. says:

above 40 deg. - no special precautions necessary

32 to 40 deg. - heat sand or mixing water to produce mortar temp. between 40 and 120 deg. at time of mixing.

25 to 32 deg. - heat sand or mixing water to produce mortar temp. between 40 and 120 deg. at time of mixing - keep mortar above freezing until used in masonry.

For all newly completed masonry:

above 40 deg. - no special requirements

25 to 40 deg. - cover newly constructed masonry with a weather-resistive membrane for 24 hours after being completed.

The use of an accelerator additive will allow removal of the protection earlier. Be sure the additive is not corrosive to imbedded metal.

    Bookmark   November 5, 2012 at 11:20AM
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our builder said we will need to tent the garage to get the brick done there. i'm going to tell them they need to heat the brick in addition to heating the tented air.

    Bookmark   November 5, 2012 at 1:57PM
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It's supposed to be 29 tonight. Our new brick was not covered. Is this a huge problem? What will happen?

    Bookmark   November 6, 2012 at 6:18PM
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Only the water in the mortar can freeze. If the chemical reaction between water and cement (hydration) was allowed to occur to an adequate level before the temperature dropped below 40 degrees, the brick should be fine although it is normal to cover it.

But no one who did not witness the work or the present condition can tell you anything for sure. You should be asking the contractor or an independent professional who observed the work.

    Bookmark   November 7, 2012 at 10:36AM
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The brick laid yesterday in the morning to early afternoon will probably be mostly fine. The brick laid in later afternoon to early evening will probably still have had enough moisture in it to actually freeze, thus halting the curing (and damaging the strength) of the mortar. I'd personally rip all of that out and redo it.

    Bookmark   November 7, 2012 at 12:44PM
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There is no way my builder will go for ripping it down. He says its ok in these temps. My husband covered part of it with tarps when they stopped working at 4 pm. It was 40 degrees then. I'm worried, but I'm
Alone in my fears. How will we know if there are issues? Will the wal

    Bookmark   November 7, 2012 at 5:34PM
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"Will the wal crumble?"

Probably not in time to make sure the builder is on the hook for it. It'll be a couple of years down the road after several freeze/thaw cycles. It could be sooner if the brick is closer to the bottom where it has more weight on it than the top where it has less.

    Bookmark   November 8, 2012 at 7:58AM
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Wonderful! I'm not sure anything can be done. My husband put a tarp over the newly-laid brick yesterday. How can they cover the brick on the front of my house when they are done today? It's rather tall and wide.
When the mortar fails will the bricks literally fall to the ground? If not, what do I look for?

    Bookmark   November 8, 2012 at 9:29AM
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