4 ms·

Umm. Why would you want to parge coat that foundation? Did you try to do that on the outside or the inside? Do you have concrete slab against ground? Cellar? O

by vlehto 8y ago

Umm. Why would you want to parge coat that foundation? Did you try to do that on the outside or the inside? Do you have concrete slab against ground? Cellar? Or is there unused airspace between the floor and the ground?

wahern 8y ago
My 1926 house, like most in SF, has an unreinforced strip foundation. (Concrete in my case, which supplanted masonry no later than 1900-1910, AFAIU.) The foundation is structurally fine (home inspection passed, earthquake retrofitters didn't seem bothered by it even though in at least one spot a installing foundation bolt blew through the concrete), but it's noticeably disintegrating. I presume the previous owner attempted a parge coat on the internal walls to hide this. My motives are both esthetic and practical. Practical because, theoretically, a proper parge coat can act as a sacrificial layer, slowing the disintegration. Whether a parge coat would actually extend the useful life of the foundation as practical matter is something only someone with real in-depth experience and knowledge of SF construction would be able to tell me. I just don't know how to find such a person. If you tour SF homes[1] you'll notice that most have remodeled the garage to include one or more bedrooms. The strip foundations are trapezoidal--slightly wider than the sill plate at the top (which is about a 1 or 2 feet above ground), expanding to much larger as it goes down 3 or 4 feet under the ground. Older remodels often parge and paint the foundation or box it behind wood molding; newer ones might actually hide it behind the refinished walls. But because of the awkward dimensions, whatever they do you can easily spot it if you pay attention. What I find crazy about this is that they're enclosing foundations which are (or will be) nearing their useful life. (SF homes are technically detached, but usually only have a few inches of gap at the most so the side walls are inaccessible.) Moreover, the refinishing is probably wrong. Either it'll pop off, or if they used a chemical binder they're (theoretically) accelerating the disintegration (the moisture and salts will create pressure behind the binder, pulling on the face of the older concrete). Likewise for impermeable[2] paint. Yet you won't even notice any of this because it'll be completely hidden. I'm happy that the home we found was (all things considered) both relatively well-maintained and unmolested. The garage was never refinished except for a parking slab poured circa 1970s. I'd like to keep it this way. [1] Which typically sit over a garage with a parking slab poured decades (or even a century) after the foundation. The garages were serendipitous. Most of the homes were built before cars were so common; what are now invariably garages were unfinished first floors intended to be used and finished (if at all) however the owner wanted--storage, workshop, in-law, extra living space, etc. When cars exploded most were turned into garages. Now in-laws and extra bedrooms are becoming much more common, either replacing the garage or reducing it to a size that would barely fit a lawn mower. Occasionally you'll find the odd house where there's still just sand at the first floor. [2] Permeability of paint is a whole 'nother can of worms. Like the foundation, the typical stucco finishes on homes on the west side of SF were designed to be semi-permeable. The external walls need to breath. But idiot painters (including whoever the previous homeowner hired) commonly use a low-permeability latex paint. (Latex comes in all kinds.) Moisture accumulates behind the stucco and the paint quickly bubbles and peels. In some cases (like ours) it can be bad enough to cause moisture damage inside the house because vapor barriers were either non-existent or primitive (our house was wrapped in tar paper), and in any event both the inner and outer walls were designed to be semi-permeable as compared to modern construction. Of course, ask most painters about these permeability issues and many or most wouldn't really understand what you were talking about, even in SF. Contractors who do a good job often do so because they've inherited a workable process (proper types of paint, etc), not because they understand why. But often times you still need that deeper knowledge to be able to debug or solve certain issues. Good luck finding somebody capable of doing that. I think that, like with modern network security, the saving grace is that most people end up dodging bullets by replacing whole systems before the consequences are realized.
- vlehto 8y ago
  Is the concrete seemingly leaking some white powder? If it is, then you have something to gain from external non permeable layer. Something like this? https://www.rakentaja.fi/keskustelukanava/img/20157/295425.jpg https://www.rakentaja.fi/keskustelukanava/img/20157/295425.j... I live in Finland. Here if the walls of a room are not completely above ground, you risk molds and therefore it's never advisable to have living quarters in such rooms. If you do have living quarters in such rooms, the proper way to do it is to install non-permeable membrane between the soil and the concrete. The renovation looks like this: https://www.vastavalo.net/albums/userpics/13316/normal__MG_1106.jpg https://www.vastavalo.net/albums/userpics/13316/normal__MG_1... If it's just a garage or storage space with no white leaks, I would just wait it to crumble to a degree that justifies changing the whole foundation. I don't see how internal coating could help anything. And external coating helps only very little if it's above ground. I'd guess SF is so arid that people don't really notice that stuff. It's different in a country like this that has swamps and rain all over.
  - wahern 8y ago
    There's a little efflorescence, but nothing out of the ordinary for the area; it's more uniform and nowhere near as severe as your picture. I suspect installing a barrier wouldn't make any sense. Because of how houses (and foundations) abut, largely limiting access to within the property's footprint, I imagine it would be easier to simply pour a new foundation. New foundations are increasingly common, but I'd rather not drop $30,000+ before I need to. SF is coastal and foggy. Most of the western half of SF is built on sand dunes. Drainage is excellent but the ground is nonetheless perpetually wet. One of the things I've always noticed about typical first floor remodels is that they always feel very damp. They may be fancy and expensive but they always feel like jail cells to me. We recently toured a house around the corner from us with a 1990s- or 2000s-era first floor remodel and, indeed, you could both smell and see mold. Unless you pour a new, modern foundation (or somehow manage to install an external barrier) I don't think it can be avoided. It's crazy to me that people pay premiums for such remodeled houses. Like I said, I'm glad the house we found was relatively unmolested. You're probably right that the reasonable thing to do is leave it alone and replace it when it gets too far along. But then I'd have no excuse to learn an old-school masonry skill. :)

by vlehto 8y ago

wahern 8y ago

My 1926 house, like most in SF, has an unreinforced strip foundation. (Concrete in my case, which supplanted masonry no later than 1900-1910, AFAIU.) The foundation is structurally fine (home inspection passed, earthquake retrofitters didn't seem bothered by it even though in at least one spot a installing foundation bolt blew through the concrete), but it's noticeably disintegrating. I presume the previous owner attempted a parge coat on the internal walls to hide this. My motives are both esthetic and practical. Practical because, theoretically, a proper parge coat can act as a sacrificial layer, slowing the disintegration. Whether a parge coat would actually extend the useful life of the foundation as practical matter is something only someone with real in-depth experience and knowledge of SF construction would be able to tell me. I just don't know how to find such a person. If you tour SF homes[1] you'll notice that most have remodeled the garage to include one or more bedrooms. The strip foundations are trapezoidal--slightly wider than the sill plate at the top (which is about a 1 or 2 feet above ground), expanding to much larger as it goes down 3 or 4 feet under the ground. Older remodels often parge and paint the foundation or box it behind wood molding; newer ones might actually hide it behind the refinished walls. But because of the awkward dimensions, whatever they do you can easily spot it if you pay attention. What I find crazy about this is that they're enclosing foundations which are (or will be) nearing their useful life. (SF homes are technically detached, but usually only have a few inches of gap at the most so the side walls are inaccessible.) Moreover, the refinishing is probably wrong. Either it'll pop off, or if they used a chemical binder they're (theoretically) accelerating the disintegration (the moisture and salts will create pressure behind the binder, pulling on the face of the older concrete). Likewise for impermeable[2] paint. Yet you won't even notice any of this because it'll be completely hidden. I'm happy that the home we found was (all things considered) both relatively well-maintained and unmolested. The garage was never refinished except for a parking slab poured circa 1970s. I'd like to keep it this way. [1] Which typically sit over a garage with a parking slab poured decades (or even a century) after the foundation. The garages were serendipitous. Most of the homes were built before cars were so common; what are now invariably garages were unfinished first floors intended to be used and finished (if at all) however the owner wanted--storage, workshop, in-law, extra living space, etc. When cars exploded most were turned into garages. Now in-laws and extra bedrooms are becoming much more common, either replacing the garage or reducing it to a size that would barely fit a lawn mower. Occasionally you'll find the odd house where there's still just sand at the first floor. [2] Permeability of paint is a whole 'nother can of worms. Like the foundation, the typical stucco finishes on homes on the west side of SF were designed to be semi-permeable. The external walls need to breath. But idiot painters (including whoever the previous homeowner hired) commonly use a low-permeability latex paint. (Latex comes in all kinds.) Moisture accumulates behind the stucco and the paint quickly bubbles and peels. In some cases (like ours) it can be bad enough to cause moisture damage inside the house because vapor barriers were either non-existent or primitive (our house was wrapped in tar paper), and in any event both the inner and outer walls were designed to be semi-permeable as compared to modern construction. Of course, ask most painters about these permeability issues and many or most wouldn't really understand what you were talking about, even in SF. Contractors who do a good job often do so because they've inherited a workable process (proper types of paint, etc), not because they understand why. But often times you still need that deeper knowledge to be able to debug or solve certain issues. Good luck finding somebody capable of doing that. I think that, like with modern network security, the saving grace is that most people end up dodging bullets by replacing whole systems before the consequences are realized.

vlehto 8y ago
Is the concrete seemingly leaking some white powder? If it is, then you have something to gain from external non permeable layer. Something like this? https://www.rakentaja.fi/keskustelukanava/img/20157/295425.jpg https://www.rakentaja.fi/keskustelukanava/img/20157/295425.j... I live in Finland. Here if the walls of a room are not completely above ground, you risk molds and therefore it's never advisable to have living quarters in such rooms. If you do have living quarters in such rooms, the proper way to do it is to install non-permeable membrane between the soil and the concrete. The renovation looks like this: https://www.vastavalo.net/albums/userpics/13316/normal__MG_1106.jpg https://www.vastavalo.net/albums/userpics/13316/normal__MG_1... If it's just a garage or storage space with no white leaks, I would just wait it to crumble to a degree that justifies changing the whole foundation. I don't see how internal coating could help anything. And external coating helps only very little if it's above ground. I'd guess SF is so arid that people don't really notice that stuff. It's different in a country like this that has swamps and rain all over.
- wahern 8y ago
  There's a little efflorescence, but nothing out of the ordinary for the area; it's more uniform and nowhere near as severe as your picture. I suspect installing a barrier wouldn't make any sense. Because of how houses (and foundations) abut, largely limiting access to within the property's footprint, I imagine it would be easier to simply pour a new foundation. New foundations are increasingly common, but I'd rather not drop $30,000+ before I need to. SF is coastal and foggy. Most of the western half of SF is built on sand dunes. Drainage is excellent but the ground is nonetheless perpetually wet. One of the things I've always noticed about typical first floor remodels is that they always feel very damp. They may be fancy and expensive but they always feel like jail cells to me. We recently toured a house around the corner from us with a 1990s- or 2000s-era first floor remodel and, indeed, you could both smell and see mold. Unless you pour a new, modern foundation (or somehow manage to install an external barrier) I don't think it can be avoided. It's crazy to me that people pay premiums for such remodeled houses. Like I said, I'm glad the house we found was relatively unmolested. You're probably right that the reasonable thing to do is leave it alone and replace it when it gets too far along. But then I'd have no excuse to learn an old-school masonry skill. :)