I have a wall that is cracking in a couple of places. Two important points:
- This wall is not part of a building, it's like a fence or property boundary wall, but it's made of blocks of some sort, covered up so they look like one continuous surface
- It's not really so much cracking as it appears to be separation along the joint lines of the blocks. It goes all the way from the front to the back of the block.
There are two places in the wall which are cracking and both are near trees, so I'm wondering if the roots could be pushing up the ground under the wall and causing the cracking. None of these trees are on our property, so we can't remove them.
One of the set of cracks is occurring near a corner in the wall, and the cracking has formed a stair-step pattern starting about 15 feet from the corner and moving up towards the corner to within about 3 feet. When we purchased the property 3 years ago the previous owners had put expansion foam in the cracks to seal it (the cracking was around 3/4" or less, but within the last few months there was movement and now the cracks are at least double that.
My initial thought was to perhaps seal up the sides and pour mortar mix or concrete mix in the opening from the top. However there are a number of problems with this: due to the stair-step nature of the cracking, the mix wouldn't go all the way to the bottom; (but conversely, I don't know how I would force the mix into cracks to make it go all the way through); if the problem is caused by the ground moving it might just crack more as the ground continues to move, possibly in a different location on the fence, and I'm not sure concrete or mortar mix would hold the fence together against such forces anyway.
I'm trying to find a solution that will fit in the budget, i.e. I can't afford to have the fence removed to fix the ground and the replaced or something like that. I can afford some raw materials, but all the labor is going to have to be myself. Are there any solutions that will allow me to effectively deal with the problem?
Best Answer
Short answer is: there is no quick fix with any kind of patching material. The trees will eventually destroy the wall.
You said the trees are not on your property so you can't remove them. You can however remove any part of them that does come over onto your property including the roots.
The only way you can affect a long term fix is to excavate behind the wall removing the offending roots and heavy soil. Replace it with sand or light gravel to increase the drainage and reduce the attraction of organic growth. You can rent a mini-excavator for a few hundred dollars and have the sand delivered for around $100 a dump truck full. Depending on the size of the wall you could get out of it for less than $1000.
After excavating, and before backfilling you need to straighten the wall and insert 1/2" re-rod into a core every couple feet and fill it with light concrete mix. This will help to stop the cracking from happening again in the near future and support the wall for backfilling. Let it cure for a week before backfilling. People falsely believe that the mortar between concrete blocks gives them strength, the truth is the mortar is only there to seal the joints. A poorly reinforced block wall is easily pushed in. Sounds like whoever built the wall didn't understand this.
Good luck!