Cracks In Block Wall Foundation

vf100 · 08-19-2008, 10:30 PM

I'm looking to purchase a new house that has a concrete block foundation on a crawl space. On one end of the house, the foundation wall is about eight feet tall. I've noticed several areas where I can see daylight through the block wall. On closer inspection, the mortar has pulled away from the block and left a small void--maybe 1/32". This is only happening on vertical joints, and maybe on about 10-15% overall. The mortar is firmly attached to one block, but separated from the adjoining block. The foundation is about nine months old. Is this normal for block wall foundations, or is there a serious problem with this foundation? Thanks.

**Termite** · 08-19-2008, 11:08 PM

If the foundation is only 9 months old, there's a major problem. Some cracking can be expected in an older home, but recently performed work should not be that unstable. It is a sign of poor work, poor drainage, expansive soils, or a number of other potential problems.

buletbob · 08-20-2008, 06:59 AM

Quote:

Originally Posted by vf100

I'm looking to purchase a new house that has a concrete block foundation on a crawl space. On one end of the house, the foundation wall is about eight feet tall. I've noticed several areas where I can see daylight through the block wall. On closer inspection, the mortar has pulled away from the block and left a small void--maybe 1/32". This is only happening on vertical joints, and maybe on about 10-15% overall. The mortar is firmly attached to one block, but separated from the adjoining block. The foundation is about nine months old. Is this normal for block wall foundations, or is there a serious problem with this foundation? Thanks.

From what I am understanding from your post is that you have seen small cracks on the butt edge of the block wall, Do these cracks continue down into the next block or just stops at that block, or does the crack continue down following the mortar joint like a set of steps?. I'm thinking its just a few random blocks that the mortar had shrunk and pulled away from the adjoining block. which one applies. BOB

vf100 · 08-20-2008, 08:03 PM

The latter is correct. The separation is random and only on the butt joints. You will see one joint that has separated, then you might see another four or five blocks away. I have not seen any cracks that continued from one joint to another. I would love to go into another house with a block wall foundation at this same stage of construction, and see if this is common. Unfortunately, I live in a rural area with very few new homes under construction.

Tscarborough · 08-20-2008, 08:17 PM

If no block are cracked and the crack is not stair stepped, it is just block/mortar shrinkage, no big deal.

concretemasonry · 08-20-2008, 09:19 PM

If you have stair step cracks, that can be an indication of a footing failure.

Does the average crack width change from the bottom of the wall to the top? If so, which is the wider? - top or bottom of the wall.

Dick

vf100 · 08-20-2008, 10:40 PM

I'll have to more closely check the cracks, but from what I recall, the gaps seem to be uniform from top to bottom. The random nature of the cracks seems to indicate shrinkage in the mortar, I didn't know that the blocks can shrink as well. This is one of those unfortunate situations where the builder is about to lose the house to his banker, so I can get the house at his cost to date. But it will be no bargin if I have foundation problems in the future. Thanks for the insight.

concretemasonry · 08-20-2008, 10:48 PM

The shrinkage will come from the mortar since the block are essential cured vefore being installed - one of the advantages of block over poured where the concrete shrinks as it cures.

If you considering buying, make sure you have a structural engineer take a look at the home (not just a home inspector) before you make the investment.

Dick