Robert Lamoureux: How to properly deal with ‘spalling’


Question No. 1

Hi Robert,
My name is Jon D., I am the president of an HOA.

We’ve got some water leeching through walls in the subterranean garage. We had a contractor come out and is talking about waterproofing a couple of different ways, one from the outside and one from the inside.

The one from the outside is so outlandish in cost, it’s not even funny. We really need your guidance before we continue to research getting this repaired, after reading your article for so long we feel we can trust your impartial opinion and let us know/break down what is being told to us.

The blocks in the garage are breaking apart, and the steel is starting to show so we know this is something that we absolutely have to get fixed, but can you tell us the difference and which way we should go on this?

We certainly want to fix it but don’t want to waste money, either.

— Jon D.

Answer No. 1

What you are experiencing on the block, which is called CMU, is what we call spalling.

What happens is that the rebar that is set in the concrete within the CMU gets wet because of a lack of waterproofing. Over time, that steel rusts and when it does it expands. The expansion causes the concrete/block to break, and that is what you are seeing inside the garage.

This clearly has been going on for quite some time, because it takes many years for the rust to get so bad that this happens.

Without photos, I am surmising that on the opposite side of this CMU wall you’ve got walkways and planters of some sort. Generally, these are the types of areas that are the source of the water.

The two options that you’ve been given are both actual options and even I offer, however, only one is a permanent fix. One option is called negative waterproofing, where the wall would be “sealed” or coated in a waterproofing product, from the inside where you see the spalling occurring. This can prevent water to that area, but as we all know, water will take the path of least resistance and eventually show itself in another area.

I normally encourage people to not go this route because it isn’t a guarantee, but there are times when a property just can’t fund the proper fix and they need to “buy some time” so we do the negative waterproofing.

My first choice and the one that is a guaranteed fix is the positive waterproofing. This is the one where they’re going to charge you an arm and a leg, because of the extraordinary amount of labor involved in doing this proper fix. They’ll need to excavate on the exterior where the source of water is, and depending on what is in that area it could be concrete or planters. They have to dig down approximately 8 feet and remove all old waterproofing that existed previously. At this point, they will start from scratch and install proper waterproofing to the area, and this is what will keep the water at bay, properly.

Now, what I recommend at this same time, is to have drains installed to this area, as well. Clearly, there is water in the area and you need to mitigate that. Both of these things together will give you a water tight area and no further intrusion issues to this part of the garage.

Know that once they excavate, if they find a structural issue with this CMU, they’ll need to back off and bring in a structural engineer to call out a proper fix. It really just depends on how much damage this CMU has suffered but if you are hiring a licensed and insured contractor who is experienced in this type of waterproofing, you should be able to rely on his/her opinion of the condition of the wall.

If your HOA can fund the proper repair, I highly recommend this because it will save you money in the end, avoiding additional damage.

Good luck to you on this project,

Robert Lamoureux has 40 years of experience as a general contractor, with separate licenses in electrical and plumbing contracting. He owns IMS Construction Inc. in Valencia. His opinions are his own, 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. Email questions to Robert at [email protected].

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