Cracks between blocks and mortar

This looks like an adhesion failure between block and mortar to me. Three possibilities occur to me…

  1. Freeze damage- mortar froze before it had a chance to cure. This problem was only visible in certain areas though, not consistant throughout the foundation. Areas were about 25 sq. ft. give or take…

  2. Sloppy onsite mixing ratios/practices resulted in mortar with excessive shrinkage. areas were about the size of the amount of mortar that might have been mixed using a small electric mixer or hand-mixing in a tub.

  3. joints are a little on the wide side. this means more shrinkage.

Seems like I often see this kind of failure more often in vertical joints than horizontal ones (see brick photo).

Looks to me like hot weather and did not soak the blocks before laying .
In third picture Bricks look like weep holes but no idea why on third level. Small holes in Mortar same picture look like what we get here from mud wasps .
They can eat out the Morter to put in an insect and lay and egg in it and close the hole with mud for the baby wasp to eat and grow .


It’s at 8200 ft. and they only get about two weeks of hot weather (85 deg. F) a year. I thought the same about the weep holes but they went even higher than 3rd)

Third photo brick appears to have tuck point application at the vertical joints note the different color mortar. Were repairs disclosed?

No, and the home with the brick had this condition all over, but random. I almost never see brick with weep holes here, this is about as close as they come. Crazy Colorado masons!

Hi. Kenton, hope you had a good Christmas.

Looked at your pictures and the block work joints is telling me that it was a poorly buttered block when it was installed and untooled.
An untooled mortar joint tends to separate when drying because it was not compressed to the other block to provide adhesion, which is the purose of the tooling.

The brick joints have been tooled and I can see some areas of the joint where it has flaked off.
This is caused by the wet tooled joint having sustained cold temperatures before the initial set. A weak mortar joint would also do the same thing and both will powderize when scratched with a blunt object.

The empty butt joint above the weep holes and the round hole that I see, is a good question. I cannot explain that one unless your masons were feeling light headed from the high altitude. ha. ha.

Hope this helps.

Marcel :slight_smile: :slight_smile:

Hi Marcel, happy holidays!
Tooling the joint would compress the mortar at the outside face of the block, but thinking back to the block I’ve seen applied, they buttered the end, set the block in place, then tapped the end with the butt of the trowel handle to make sure blocks in the same course had a good connection end to end.

If they fail to tool the joint, I can see how that might slowly allow moisture into the joint, which could create some separation over time from freezing, but I’m wondering whether that gap went all the way through and how this type of work effects the structural integrity of the foundation. Couldn’t see the interior.

:slight_smile: :slight_smile:

Structurally, a bad buttered joint on block is not that critical, for the bed joints actually do a lot of work in the design and the durawall reinforcement every 16" vertically add to make up for a loose butt joint.

Water tight, no.
Right, no.
asethetically pleasing no.
quality controlled, no
easily repaired, yes

Masons lay block from one side and usually that is the side that is the best looking, so if the pictures you posted are the side they were working on, it is guaranteed that the other side is worse.

Good masons will butter a block while it is standing up and then lay it in place, but guaranteed most just slap the mortar with their trowel to the block that is laid and when not done properly, not enough mortar is installed.
Some will even tweak the block forward with their trowel when they notice they are loosing bond and would create a void in the joint.

Possibilities are endless, therefore assumptions are too, and I guess noting what you see and move on would be power for the course at this point.

Marcel :slight_smile: :slight_smile: