Connect to your favourite weather forecaster and look for the following conditions:
Category: Masonry Product: Brick Mortar
Temperature Limitations: Use above + 5 C (+40 F)
Rain Limitations: No standing water or wash out prior to setting
Wind Limitations: Protect mortar if wind will dry surface too rapidly
Humidity Limitations: The higher the humidly the better for mortar strength
Continuous Conditions: Keep damp and frost free for 48 hours.
Comments: Mortar should be mixed as dry as possible, but damp enough to keep its shape. It must be protected both from frost and from rapid drying as it gets it strength from a chemical reaction that requires moisture -- drying rapidly will actually make it loose its strength. Mortar requires a two step mixing process - initial rather dry mix -- let it rest 30 to 45 minutes then add water until it is workable. Only mix what you can use in 45 minutes after the second mixing as it sets rather quickly.
Weather limitations on most renovation products can be located on the WEATHER tab above.
APPLICATION / INSTALLATION DETAILS
It is often said that brick or block mortar is not designed to hold bricks together, but to keep them apart.
In fact it is not a real good "glue" and it is purposefully made softer than the materials it separates. That is because it is considered sacrificial with respect to building movement.
If things shift, something is going to crack, so it is planned ahead of time that the mortar will crack before the bricks or blocks crack. Mortar is easier to repair -- or "repoint" -- than replacing bricks or blocks. That is why cracks in a brick wall show up as a zigzag line flowing between the bricks.
One of the biggest errors someone can make is to use a rigid mix, like a strong cement mix, to replace mortar for when the building shifts again, the bricks will crack rather than the mortar and you are in for major repairs.
Another critical thing to keep in mind if you are repointing bricks is that mortar does not stick to mortar, it sticks to bricks. So if you simply apply a thin layer of mortar over a crack, it will not stay. You have to remove the old mortar to a depth at least as deep as the joint is wide, and then force the new mortar firmly into that space so that it is pushed up against the two bricks. Then it will stay at least until the building shifts again.
Mortar failures are often related to not adjusting to weather conditions when working with the mortar.
For details check out WORKING WITH MORTAR IN HOT & COLD WEATHER.
For lots more information look up the keyword MORTAR in the database.
You may want to compare using regular mortar to a small job quick fix by checking out Weather Restrictions: LATEX MORTAR PATCH MIX IN A TUBE.