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ChrisJJ 03-30-2011 02:43 PM

Garage CMU partial wall - shifted block
Hi, We are finishing a garage remodel (yes we do have a building permit). I've started to prep the CMU walls for painting and noticed an irregularity with one wall. I don't think it's a big deal but I thought I'd ask here.

Background: Our garage is partially below grade. In the rear there's 4' CMU wall and on the side there's a 2' CMU wall. Outside the ground rises gradually along the 2' wall to the rear of the garage. There's a downspout at the corner where the 2' and 4' CMU walls meet.

When we moved into this house in 2001, the downspout emptied just a foot or so from the corner and the water ran down the grade along side the 2' wall to the driveway in front and then down to the ditch. We never saw any water in the garage but it didn't seem right to me. So a few years ago, I piped the run-off to 10' away from the garage and made a swale to direct the water to the side yard.

Back to today: I just noticed that one end of a CMU block (17 inches from the corner) has been pushed out of alignment, about 1/8th inch inward. This block is on the 2' wall and around it there's cracks in the mortar running like stair steps from the top to the bottom and some of the mortar is loose. I had noticed the cracks but never noticed the protruding CMU block or loose mortar before. (in my defense, before the renovation, this garage, a 24' x 25' space, had 1 piddly ceiling fixture in the middle and it was hard to see much of anything in this corner.)

I'm no genius but I think it's a safe bet the offset CMU was caused by the previous poor drainage. I'm thinking that since the run-off problem was fixed and this is such a short wall, I can replace the broken mortar, fill the smaller cracks with caulk and forget about it. But before I do that I thought I'd run this past you folks. Is this a potentially big deal or not?

jomama45 03-30-2011 04:16 PM

Your best bet is to spend a little more time surveying how much the wall has moved. A dry line strung tight from one end to the other at the top of the wall will tell you much more. A picture wouldn't hurt either.

ChrisJJ 03-31-2011 10:43 AM

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I just checked the alignment of the wall and I was surprised to find it is bowed inward at a about 5/16ths of an inch.

I've included a couple of photos. The displaced cmu is the second from the right, under the cap blocks (is that the right word - the half sized blocks to sit on top). I've included a photo taken from above to show how much it's shifted.

I was mistaken when I said the mortar was loose. Nothing was moving with finger pressure and I even went around to see if any would loosen with a hammer & chisel. The mortar was holding tight and I stopped as I began to think that if it's so determined to stay, maybe I should let it.

As you can see in the photo, the slab has dropped down. To the left, just out of the picture there's a big old crack running perpendicular to the wall. This is typical in the neighborhood as the developer cheaped out 40 years ago when pouring slabs. Everyone's slabs are cracked and shifted. I've decided to patch cracks and caulk seams but we're otherwise going to live with it.

So what do people think I need to do about this 2' cmu wall? Should I caulk the cracks and fill the bigger gaps with patching compound (I figured I'd push it into that deep crack near the slab with one of those bags with the nozzle - can't think of what they're called - like what bakers use to decorate cakes.).

I forgot to mention before that the wall above is not load bearing (this is the gable end of the garage).

CplDevilDog 03-31-2011 02:38 PM

I would treat it as a cosmetic situation for now. If your concerned, measure the gaps with a set of spark plug gauges and keep track of them for a few months. Also, you can glue a glass slide for a microscope across the crack and see if it breaks in a few months.

jomama45 03-31-2011 05:36 PM

The wall doesn't appear too bad, just needs some tuckpointing.

The top course simply looks like what I would call an 8" half course solid.

Has the floor really settled 4"+?

concretemasonry 03-31-2011 07:48 PM

Instead of the floor settling it looks strangely like what you see in a basement with a true floating slab that is poured late in the job and is poured on the footing (4" wider than the wall on each side) for a stem wall and the slab also bears (hopefully) on the compacted soil after the utilities and drains are in so it can be finished with a slope for drainage.

I would not worry about the wall strength and just tuck point the cracked joints. It is surprising there is no sill plate to be seen, but the wall could be 12" thick with the sill set toward the outside surface of the wall. A sill with anchor bolts prevents uplift and tends to prevent lateral movement.


Jbyrd 03-31-2011 08:19 PM

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In my old garage that is built like yours, on the outside there was 2 railroad timbers that the previous owner used to terrace the yard, over time they pushed into the blocks and pushed the wall in and inch. I removed the timbers on the outsided and poured concrete down the cavities with some rebar' because they used 2x6's for a sill. I then took my old garage and converted it into 2 rooms. I built a subfloor with 2x4' and used plastic and insulation under the floor. I ended up with 2 rooms 1 bedroom and 1 family room.

ChrisJJ 03-31-2011 09:11 PM


Originally Posted by jomama45 (Post 620886)
The wall doesn't appear too bad, just needs some tuckpointing.

The top course simply looks like what I would call an 8" half course solid.

Has the floor really settled 4"+?

No it's settled more like 1/4-1/2 inch in that corner. You can see the seam just above the slab.

jomama45 04-01-2011 10:05 AM

OK, it just seems like they would have poured it to cover what looks like the last course of below grade block. If you look close, the first & second course from the bottom are "stacked bond". (the head joints line up)

concretemasonry 04-01-2011 12:27 PM

After reading the posts more thoroughly and looking at the photos, it seems than the corner of the foundation (slab wall a section of the wall settled). This was probably due to the poor drainage the reduced the support from the soil on that area.

The fact there apparently "2 step cracks" on one wall near the corner is a classic indication of settlement of the footing. These cracks decreased the bond, which could allow a small lateral movement. The clincher is the fact that there is a slab crack perpendicular to the wall (out of the photo) that was caused by the footing going down and reducing the support on the edge of the slab, but held long enough for the soil to move and allow the crack.

Make sure the drainage around the corner and outside of the footing is adequate enough to stop any further settlement. Point up the existing cracked joints and then just watch. If the drainage is not good, settlement could continue somewhat.


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