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Crumbly foundation


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I am inspecting a lot of older homes with foundations that were crumbling so they have been skim coated (older basements mostly). I am curious as to what others write in their reports when the original foundation is no longer visible due to the skim coating.

Also, when tapping on the skim coats on most of the homes you will hear a hollow sound at least in areas so there is no bonding between the materials. The skim coat often is breaking back off the foundation as well in some areas.

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Mike,

I typically see this material installed on foundations with crumbly concrete. I understand that it is waterproofing to a point, but usually breaks up. My concern is that when tapping on the material, you will hear hollow sounds in areas and you have to wonder how thick the original concrete is at this location. There are many times when the skim coated material/ parging has broken off and deteriorated concrete is visible.

Now take a home that has been recently coated. The basement is finished so there is no way of inspecting the foundation on the interior and the exterior is no longer visible. How do you check for signs of cracking, etc. I have always at least written up the foundation as inaccessible, but was wondering what wording others used if any.

How do you decide when a concrete wall has gotten too crumbly for skim coating/ parging?

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First, it's not waterproofing. One does not try to stop a leak in a boat by sticking gooey stuff on the inside of the hull. Trying to stop or impede moisture entrance by "waterproofing" the interior of a foundation doesn't work either.

Personally, I don't call smearing mortar on the interior of a foundation *parging*, as parging is an application of mortar applied to masonry primarily as a waterproofing measure. Since no waterproofing is accomplished, how can it be parging?

Traditionally, parging is applied to the outer face of a masonry wall to control water penetration, or to the inside face of the outer wythe of brick on a multi-wythe wall for the same reason (not a common practice for at least 40 years). The term has been bastardized (similar to tuckpointing) to describe any smearing of mortar on masonry.

What you're seeing is the misguided attempt by unknowledgeable individuals to "fix" something. Call it parging if you want, but since it's not doing anything to provide waterproofing, I think parging is the wrong term, even though everyone uses it.

The hollow sound you are hearing is the moisture in the foundation pushing the mortar coating off the wall. There is no way you can know the degree of deterioration without tearing it all off. I doubt that the foundations you're seeing are badly damaged, but since you can't know, the safe bet is to say you don't know.

When I see this activity, my approach is to think more about stopping the water entrance, which is causing the problem in the first place. If you can stop the water from the exterior, the interior "parging" becomes unnecessary.

Of course, this is often problematic and expensive, which is likely the reason someone smeared mortar on the interior in the first place; it's cheap, it looks pretty, and it made the applicator think they'd done something worthwhile.

When I find this, I write it up as dampness, possible defects, and poor repair practice. I have several other comments I often apply, all dependent on the specific conditions of the property.

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Kurt,

I agree with you- is there any documentation out there that I can base my report on when writing up the reports.

The reason I asked this question is that the skim coating has never seemed to me to do any good for keeping out moisture (especially when it is installed on just the exposed surface of the basement foundation on the exterior). I typically see this coating applied when the foundation is getting crumbly and they are just covering the exposed deterioration and attempting to help prevent further deterioration (above grade again).

Any books or other forms of documentation would be helpful.

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Originally posted by Brandon Whitmore

I am inspecting a lot of older homes with foundations that were crumbling so they have been skim coated (older basements mostly). I am curious as to what others write in their reports when the original foundation is no longer visible due to the skim coating.

Also, when tapping on the skim coats on most of the homes you will hear a hollow sound at least in areas so there is no bonding between the materials. The skim coat often is breaking back off the foundation as well in some areas.

In the Portland area, the exterior, aboveground portions of the foundations were routinely parged with a layer of Portland cement plaster right from the get-go. This was not a repair; it was done to improve the look of the foundation by eliminating the ugly form impressions and by mimicking the look of stucco. Occasionally, they'd parge particularly ugly sections of the interior walls too.

In Connecticut, where I first started working in construction in the 1970s, the crews would do the same thing. I don't know if it's still done there. The hollow sound is unimportant. It just means that the parge coat has loosened. It says nothing about the concrete beneath it.

Many of our pre-war Portland foundations are crumbly. This is unrelated to the parging (or stucco, or plaster, or whatever you want to call it.)

Truly crumbly foundations in Portland can almost always be traced back to aggregate that came from the Rose Park Quarry. This stuff was dirty and might have even been salty. As local engineer & concrete expert Jay Kushner has explained, dirt & salt are like a virus in concrete. They work to break it down slowly over a period of decades.

If I can get to the actual wall, I go at it with my rock pick. If the soft stuff stops within a few inches, the wall is generally going to be fine. If the softness just keeps going, & going, & going, then it's time to call in an engineer.

My engineer of choice for these projects is Jay Kushner at Seismic Technologies - 503 203-8337. He knows Portland foundations.

As I recall, when one of these foundations is crumbly enough to merit repair, he casts new concrete next to it. I think he described the old crumbly foundation as a mattress standing up on it's end, all soft & squishy. His repair is like strapping a sheet of plywood to the side of the mattress to stiffen it.

- Jim Katen, Oregon

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That's interesting; we've done the same thing.

Placing a new concrete wall along the existing wall, and tieing them together w/rebar, is a decent way to repair failed foundations.

We've done a few of these interior "foundations" on old telephone tile also.

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Jim K and Kurt M,

I think Brandon has opened a can of worms for himself. I think an inspector must call the technique anything that is readily understood by the locals. Here is Mich, there are only 14 people that use the term "parge" and two of us can't spell it! From a purely technical view, is parging a technique, material or end product? What type mortar is used in parging? When you "thoro-seal" block, on exterior, is that parging or damp-proofing? Does it make a difference what you call it if it is above grade? etc.

From a report writing view: If you can't see it, don't guess about it and write what you know. I know Jim K and Kurt M have seen thousands of foundations that are crumbly and working just dandy.

It really helps when you have the local knowledge that Jim K has. Kurt M works with more brick than God, 'cause that is what Chicago is.

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Originally posted by Brandon Whitmore

Jim,

don't you see foundations that have a more recent skim coat as well? The one I did yesterday looked like newer work and just makes me wonder what was covered up.

I occasionally see patches in the old parging. Sometimes I see an entire wall that's been recently re-parged. If they're in good condition, I don't say anything. If they're in bad condition, I recommend repairing them.

How about the skim coat that projects beyond the siding where the materials meet? (or is touching the foundation)-- how do you address that?

On most of the houses that I see this on, there's a piece of trim called a water table between the foundation and the siding. The parging usually just butts up to the water table. I've never seen this cause a problem.

- Jim Katen, Oregon

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Kurt-

I have bounced back and forth with the wording above- sorry.

This is in regards to any of the older foundations that are coated on the interior or exterior of a foundation.

In my last home I inspected, the interior basement was recently finished and the foundation was not visible-- so the exterior was visibly coated. (I just wrote up the foundation as inaccessible as a result)

I know at least some of the coating was replaced, because there was a section of crawlspace where there were cracks in the foundation that did not show through the coating, and some that did (foundation has dropped about 1 inch at one corner of the home to where the siding no longer overlaps the foundation).

I was keeping the question a little vague to see what I could learn from the masters

Thanks for all the above info.

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It is a term I usually hear regarding a soft brick chimney that was crumbly and they parged over it with a "mortar". Usually type S that will become more brittle than orig brick structure. Parging will crack and fall off when structure moves. Falls off anyway, but it makes folks feel good and it looks pretty for a time.

We also have two part "parging" that is common on exterior ridgid foam board foundation insulation. Any tiny crack or void provides safe and comfortable harbor for carpenter ants in the foam board and sill.

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  • 2 weeks later...

Parging was usually applied to the exterior of a foundation, and its function originally was moisture resistance for the foundation. This method is still routinely used in some areas. Applied to the interior of a chimney flue, its function was to keep flue gases from leaving the flue through the chimney wall. Applied to the exterior of a chimney or interior of a foundation, its function might be the same. However, some masons or do-it-your-selfers will use this method to slow down or cover up deterioration. Ultimately, we just write what we see. If the parging is deteriorated, then repair is necessary. It would also be important in this instance to note what is happening on the exterior of the foundation.

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