large stair step cracks in cinder block corner

radar4 · 08-07-2012, 10:20 PM

Our cinder block garage has suddenly developed stair step cracks in 2 corners diagonal to each other. we have removed 2 huge oak trees from the area recently and put on a new roof. since then the cracking has accelerated. would appreciate some advice on what to do now. There was some cracking going on in one corner at the bottom of the garage for some time but now it has quickly spread up the mortar to the top of garage. Separation of block is about 1" at the bottom narrowing to about 1/4" at the top. Any thoughts would be appreciated. Thanks

jmagg · 08-08-2012, 08:30 AM

Sounds like the vibration of removing the trees and/or stump grinding, may have caused the increased separation, which is probably indicative of a footing problem. Also, any changes in drainage may have caused settling.

If the separation isn't worsening, I would try tuck pointing the joints first, before rebuilding. When pointing (filling the cracks), the joints must be full and compact. Remove the old mortar, with hammer and chisel. Large voids may need to have some type of backer, to accomplish a compact joint. You should not be able to push the mortar through. Prior to pointing, the joints should be clean and dust free.

radar4 · 08-08-2012, 10:05 AM

Do you think the fact that we recently reinforced and shingled the roof has something to do with this? Also we are in a terrible draught, the trees were removed after we noticed the serious cracking. We found one BIG root going thru the brick below grade and think we should look for more, but are worried about doing more damage. Any thoughts would be appreciated. Thanks

joecaption · 08-08-2012, 10:12 AM

#1 Post a picture.
#2 I would never suggest using a chisle except to knock out some of the big loose chunks.
Use a 4-1/2" right angle gringer with a diamond wheel instead.
I be concered a chisle may do damge to the blocks.
I also wet down the area of the repair so the block does not suck out the moisture out of the morter.
If you pick up a morter bag when you pick up the morter you'll find it far less messy a job.
Works like a pastry bag.

radar4 · 08-08-2012, 10:22 AM

I will post a picture as soon as possible. Thanks to you both for trying to help us.

joecaption · 08-08-2012, 10:30 AM

As that old root starts to decompose it's not going to make things any better.
It's also a great way to let in termites.

May sound like chicken little but that's the way it is in real life.

Sometimes it requires digging out to the footing, digging out that old root, and mud jacking up the footing to get it back were it belongs.
And to be proactive once that's done get a termite treatment.

I went through this with my own house and it worked for me.

jmagg · 08-08-2012, 10:37 AM

The more water used in a mortar mix, the more shrinkage will occur, but yes a semi damp joint will better the bond. A sharp chisel would be my tool of choice considering the mortar is separated on one side, giving the old joint room to displace.

jcarlilesiu · 08-08-2012, 12:47 PM

A one inch crack is too large to tuck-point.

The step cracking in the corners typically represents differential settlement.

radar4 · 08-08-2012, 02:59 PM

Thanks for your idea. If it is differential settling as you suggest, what do we have to do to stop it from progressing and how do we know if it is?

Canarywood1 · 08-08-2012, 07:02 PM

If i were to guess,i'd say the drought your experienceing is a big factor in what's happening to your walls.