Crumbling, 'spaling' exterior foundation walls
I've got a problem with crumbling exterior foundation walls somewhat similar to what's addressed on this post:
The wall was skim coated before this summer and signs of the spaling were covered by the skim coat. The large cracks visible in the photo are shallow and only go as deep as the skim coating that is suddenly falling off in large chunks.
The crumbling is bad enough that I can flake off the concrete with my bare fingers. I have not yet dared to dig into it to see how deep it goes. There is not a ton of evidence of significant moisture in the basement but there is one clear vertical crack and efflorescence at *other* points around the foundation. There is also an interior 'pony' wall between the full-height basement and a crawl space and that wall is spaling *very* badly.
This is on a 1924 2-story house on a raised lot with decent (but imperfect) grading in western Oregon. So there is a lot of rain and moisture but not a lot of extreme cold.
I've done a number of concrete repair projects and initially looked into doing this one myself but the more I got into it the more I felt like I was out of my league and decided to get bids from some pros. That's actually where I started to get a bit lost. I've had two contractors come out and they suggested totally different approaches. I'm hoping some of you can give me opinions about the approaches.
Number one suggested digging out the loose material, hand-washing and prepping, re-building those sections with hydraulic cement to 10" below grade, then skim coating. That's all.
The other contractor suggested doing nothing to the exterior at all but doing a bunch of work for interior reinforcement and water abatement. They suggested putting carbon fiber reinforcements similar to what's described here:
Then putting in a basement floor drainage system on the foundation footing, along the perimeter, adding a sump pump, a hefty dehumidifier, removing my old vapor barrier in my crawlspace and installing a multi-layer sealed replacement much like this one:
I can understand the need for water abatement but the wall is not flexed or bowing in any way, nor are there horizontal cracks so the carbon fiber strips are a bit of a mystery to me. Also, the basement has never had any standing water or weaping walls anything like that in the 7 years that I've lived in the house. I also don't understand how all of the water abatement and interior reinforcement is much good if the exterior wall is left as-is with crumbling material exposed to the elements.
I've also had someone else more casually mention the possibility of using Gunite or Shotcrete in the interior.
I think you have had salespeople with an answer looking for a problem.
If this house was built today, it would have a perimiter at the level of the footing to take water away. It would also have waterproofing of some kind on the outside of the foundation to prevent water from penitrating the concrete. It would also have 6 to 8" of concrete showing above ground level without waterproofing.
This is all done because concrete is not waterproof and water will cold to warm thru the foundation. On the inside it may not be noticible do to evaporation but in the summer it wants to travel to the out side where the heat is and runs into paint. the weakest part of your system is the skim coat that may not have a good bond to the concrete or in itself could have a water restrictive feature.
The simple question is, is there any dammage to the foundation below the ground level, where the water can come and go as it pleases.
Hi nealtw - thanks for your reply. Yes, I tend to agree that the second contractor in particular seems to be pushing a sale but I'm no expert on foundations so a little confirmation of that is helpful. I don't really know if we have damage below grade. The only visible evidence of it is the one vertical crack in the basement that I mentioned in the first post. It is long but not particularly wide - just a thin line. I'd have to excavate to know more.
It is a 1924 home with the original foundation so construction quality seems to be in line with the times. The cement seems to have issues similar to what I've seen others post about on this forum with regard to houses of the period. There is more concrete/mortar and less stone/gravel than I'm used to seeing in modern concrete mixes and the stone that is present is often larger than typical concrete gravel. As far as I can tell there is no evidence of any kind of waterproofing on either the interior or exterior. There is a good two feet of exposed concrete above grade before the siding starts.
The skim coat is weak, yes, and I'm not surprised that it is popping off. That's annoying and ugly but what really worries me is the crumbling of the concrete beneath.
Well I am no expert either but I will bet that the green paint is oil base and not letting the concrete breath.
Where in Oregon are you? If within reasonable driving distance from Cottage Grove, I'd consider driving to your place and giving your foundation a quick look-see--might have to hit you up for a cup of coffee, though. A half-hour, hands-on site review would enable me to give you my best take on what you really have and how best to correct it.
I'm semi-retired now, but while a working stiff I performed more than 3550 agency and private inspections of concrete, steel and timber structures, starting in 1967. As well as developing and administering many structure rehabilitation and repair plans for many of those structures. I was a professional engineer licensed in 7 states at one time, but am allowing my licenses to expire as they come up for renewal--can't afford the grand a year they were costing me without any income to show for it. My looking at your foundation shouldn't get me in trouble with the State P.E. board (Oregon P.E. expired a few months ago), as I wouldn't be charging for my services, just giving an acquaintance my opinion. PM me if you'd like my help.
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