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Robert Lamoureux: New block wall is cracking up

Your Home Improvement

Posted: November 26, 2011 1:30 a.m.
Updated: November 26, 2011 1:30 a.m.

Hi Robert,
First-time question, long-time reader. I’ve got a block wall that is cracking out the concrete in between the blocks. It looks like stairs. The crack goes over, down, over, down, etc  This wall was just put in less than one year ago. What is this indicative of? 
Marley E.

Hi Marley,
This is either a footing or compaction problem. The stair effect is movement caused by undermining below grade. Typically, when you see this type of damage to the mortar lines, it’s due to a cracked footing that is no longer supporting the weight of the wall. Or, it was poorly compacted when the wall was built. 
There’s no way of knowing what will happen as time goes on. It may have finished settling or the damage could worsen. If the wall is less than a year old, I would have the contractor come back out and make it right. 

Hello Robert,
I’d like to remain anonymous. I just want to make a comment. I’ve pulled permits in other cities around Los Angeles, but never Santa Clarita.
I was doing some work in Santa Clarita, and I remembered you saying how friendly the building department was here. I pulled my first permit in this city, and I have to say, hands down, what a delight the building department is in Santa Clarita. 

Like I said, I’ve had experiences all over Los Angeles county, and you feel like you’re doing them a favor. Here though, these guys are the best. So just so you’ll know, the city got some revenue, and I’ll be back.

Hello Mr. Lamoureux,
I’m a board member for a homeowners association. This is actually the second question from our homeowners association. You might remember a question about what to do to help prevent our stop signs from being run over? We followed your advice and everything is fine now. 

We have another situation, however, regarding waterproofing. We have 52 three-story units in our development. We park our cars under the bottom level. The front wall is showing signs of water leaks, some more severe than others. 

If you go to the front of the buildings, we have balconies that are two feet off of the ground. Will this require excavation? If so, how could we excavate and very inexpensively waterproof those areas? Thank you,
Gina T.

Hi Gina,
There are two types of waterproofing. Positive and negative. Positive means you would dig down and apply the waterproofing to the outside of the building and backfill. This is the best way, but costs more due to the labor involved. 
Negative waterproofing means you would apply the material to the inside of the garage wall. For this, you would first need to remove anything that was attached to that  leading wall of the garage.  You probably have four or five feet of block that then transitions into a regular wood frame construction. I’m speaking in generalities, but this is typical in what we call tuck-under parking. 
After everything is removed, get that wall sandblasted. Depending on how the walls are divided from unit to unit, there could be a 2” x 4” or 2” x 6” wood frame that you won’t be able to waterproof unless you remove that drywall and the framing.
There are a couple of different products you can use for negative waterproofing — Drylok and Xypex, pronounced zypex. I’m not going to bore you with all of the application procedures, but once you get the wall sandblasted, just follow the manufacturer’s recommendations. 
One of the problems inherent with negative waterproofing is that inside the block, you’ve got rebar. Although you can prevent the water from coming out of the wall, for a while, it will still be seeping in from the back side and will be trapped inside the block.  Over the years, the constant water on the rebar will cause it to rot because it’s steel. And eventually, somewhere down the line you will get failure. 
I don’t recommend negative waterproofing, but if your immediate budget is your primary concern, weigh the consequences and make your decision. Ideally, you always want to go with the positive.
Hi Robert,
I have a bad sewer line that is full of roots, and has been completely obstructed by a tree on the parkway that belongs to the city. Is the city responsible? The sewer line looks like it’s a cardboard pipe with tar on it. It’s just crumbling.  We got the pipe cleared at about 7 or 8 feet deep. Can we just stop here or do we need to transition to the city line? Thank you,
John D.

Hi John,
Regarding the tree, that’s going to be between you and the city. Given the pipe is in bad of condition, I would not risk it. If you’re that deep, I would not leave it there. I would take it straight to the city clay line and put in all new pipe. 
I know this is an expensive endeavor, but at this point, finish the job and do it right. Go back and put in ABS or clay. I would use ABS and glue all the connections thoroughly.
During the backfill, you’ll want to compact every foot. Get it wet and use a tamper. Make sure you don’t crush your new line. Then repeat at every foot. If you have a bit of a hump when finished, that’s ok. It will settle over time. 
You’ll want to shade your pipe. This means that the pipe is resting on well-compacted dirt and is being supported by the backfill. If the inspector sees that the pipe is hanging at any low spots, he will call you out on it. 
If you are transitioning from clay to ABS, instead of gluing a connection you would use a mission band. This is a rubber, bell shaped band that will connect two different sized pipes and materials. 
Everyone who sends in a question answered in this column will be given a full-color, limited edition The Signal/Your Home Improvements T-shirt. The shirt is available for pick up at IMS Construction in Valencia.
Robert Lamoureux has 25 years experience as a general contractor, with separate licenses in electrical and plumbing contacting. He owns IMS Construction Inc. in Valencia. His opinions are his own, and not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor, after that contractor has made a thorough visual inspection. Send your questions to


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