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Stone foundation

Posted by worcesterma (My Page) on
Thu, May 26, 05 at 15:27

I have a stone foundation and on the basement walls is a concrete skim coat. In some areas (I assume due to age, we don't have any water problems) the concrete is turning sandy and coming off in kind of a gritty powder. Any info on maintenance, ect?


Follow-Up Postings:

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RE: Stone foundation

Remove all the loose degraded concrete/parging and reparge the wall.


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RE: Stone foundation

There is a source that may give you more info on what to do. I'll add the link for one of the two briefs dealing with stone and masonry issues. When you bring up the link, scroll down to the bottom of the page so you can see the link to the second bulletin. (I'm posting link to the first.)

Here is a link that might be useful: Link to NPS Preservation Bulletin on Assessing, Cleaning etc. of masonry in old houses.


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RE: Stone foundation

I have a fieldstone foundation with crumbling mortar in my 1890 house. After getting a scary-high bid from a mason to chip out and re-mortar the foundation, I called in a structural engineer, who told me that the foundation was stable and that in any case mortar has no structural role -- in his view fixing the mortar was really just an aesthetic issue. So, this project has moved to the bottom of my priority list.


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RE: Stone foundation

Ive read those preservation briefs already, they don't really give a specific or detailed "how to". Wondering if anyone has any info re: specific products, methods, etc. they've used. Would rather not have to spend hundreds of $$ on getting mortar tested etc. but on the other hand, if I have to I have to...the question is, do I really have to??

I think its more than an esthetic issue, or can be--if there are cracks on outside which water gets into, the freeze/thaw cycle can lead to further damage.


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RE: Stone foundation

Had a similar problem. Initially thought it was due to age of house (house is 60yrs +) or poor materials. Turned out that this degradation was caused by water leach. During heavy rain or at the end of winter, it appears water was getting through the mortar on the exterior (between the stones). The source of my problem was poor grading and exterior drainage.

Remediation: Had to identify hollow sounding areas/spots on the basement walls (indication that the mortar had detached from stone), chisel out and fill with new mortar. For the rest of the wall used a wire brush to remove the powdery stuff, filled the mortar and flushed with the surrounding area.


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RE: Stone foundation

You can parge the joints with mortar mix sold in bags if the old lime cement has come loose. Top off with a really nice coat of cheap whitewash. Looks great and a good selling point. (people like white in old basements, looks less like a dungeon, brightens it up and looks well kept).


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RE: Stone foundation

So let me get this straight, concrete is bad (cracks the rock) but moarter mix is OK? Is there a spcitic type that is better than others?


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RE: Stone foundation

Hey! I like my dungeon-like basement! Glad I found this forum. I've got an 1840 home with stone foundation. One spot was as you described and before parging, I fixed the eaves, routed the downspouts away from that spot, graded around that area and replaced the window wells. Basement is alot drier in that spot now and recommend fixing the leak before parging.


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RE: Stone foundation

Concrete is bad because generally speaking it is stronger than the stone underneath and can cause cracking. Mortar mix is better because it's the "sacrificial" material, meaning that it's softer than the stone so it'll be the first thing to go in case of settling. You want that. So whatever mortar mix you use has to be softer than the foundation stone. Lime mortar is a wonderful material.


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RE: Stone foundation

M, S, N, and O are the types of mortar. S and N are commonly available, but are often to hard for older work.
The site below is just one that has details on mortar types and mixing. In some cases you can use an available mortar and add lime and aggregate to create the desired type.

Here is a link that might be useful: mortar types


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RE: Stone foundation

Hi there! I have a question about a stone foundation. I'm buying a house that was built in the 1830s and has a stone foundation, which our inspector said has "substantial structural defects", which means the foundations walls are bending. How serious is this problem? And is it fixable? And at what price? Thanks for any advice you can give ... we love this house, but we're not going to buy it if it's going to cause us more problems than it solves!


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RE: Stone foundation

Sedimentary rock was used to build my house foundation in 1888. Someone had the Great Idea to "SKIM COAT" the walls to make them look nice. OH.. MY.. it's falling off..! Daaa.!
If you dry out or wash water through Sedimentary rock it either drys out or washes out the the electrolytes in the Sedimentary rock. This will in time Destabilize the stone.
Yes, you have flaking stone. You should not either paint or skim coat this rock on the inside or outside of your home. Only cover it with porous breathable materials after the paint and or skim coat is cleaned or chipped off and the stones are re-tuck pointed with motor mix. If the stone can breath all year long it will stay stable for hundreds of years. So many people skim coated this beautiful rock. Look at it close up to see all the frailties that make up the properties of it and you will be able to see. It was made from nature and will stay stable if exposed to nature. Seal it up or wash it out and Good Bye foundation stability. And YES... I am part Italian..!


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RE: Stone foundation

I'm glad I found this thread. I have this exact problem in the house I just bought. So re-pointing with new mortar should do the trick then? I was thinking I needed to resurface the entire basement with new parging, but maybe that is unnecessary. I was planning on using some sand/topping mix or a concrete-sand mixture for the parging. Not doing the resurfacing will certainly save me a lot of time!


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RE: Stone foundation

am i crazy or is it a bad idea to put concrete over stone? stone naturally weeps moisture so it seems that putting essentially a vapor barrier on one side would only speed up the degradation of the stone foundation. i don't have a stone foundation, i'm just talking from theory. am i nuts?


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RE: Stone foundation

Are there anyone still posting to this Forum? If so, I would like some advice regarding> "Re-pointing an old Field Stone foundation". I have a large and old 3 family home at the top of a hill in Boston. The front half of the foundation is almost completely buried under ground. The interior walls of the foundation is in need of re-pointing. I believe it was originally filled with a lime and sand mortar mix? But I'm not sure? I need some advice as to what type of mortar to use? Any help out there?

Thank You......


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RE: Stone foundation

Yes it can be repointed using a dryish mortar mix - look for any type designated as high strength. If this is a large wall and the interior appearance of the stone is not important, it can also be sprayed with shotcrete or gunite. This is a job for a contractor and will involve some expense and mess, but will be quicker and stronger than repointing.


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RE: Stone foundation

Thanks Mainegrower,but I've heard that a high strength mortar like a (Portland)will eventually do more harm than good because of its strength!!
Correct me if I'm wrong, but all my research tells me that the original mortar used for field stone foundations like mine was a lime based sand and cement mix.
All the reasons stated for NOT using a high strength modern day mortar mix are, that. The natural moister emitting characteristics of field stone will be affected in an adverse manner if the mortar is too strong!
How true this is I don't know....Maybe you do? Either way, I'm soooooo confused!!
Are you a Mason? If so, what is the real truth?
Thanks Again,

If I'm being a pest? please forgive me!

Take care......

Blakk....


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RE: Stone foundation

Blakk: I'm not a mason but I have lived in a circa 1810 house with a stone foundation for more than 40 years and have consulted with several masons about various issues that have arisen.

Much depends on the type of stone used in the foundation. Hard stone such as granite is much stronger than any concrete or mortar. Softer sedimentary stone such as limestone is another case entirely.

Another factor is the size and style of the foundation. This can range from massive cut stone blocks through round field stone to so-called rubble walls which is what I have.

As a post above noted, often the mortar on the interior side plays no role at all in the structural integrity of the foundation. (Big gaps such as you would find in a boulder type wall do, however, provide a path for water, mice, chipmunks, etc. to enter the cellar).

In general, it is a big mistake to attempt so-called waterproofing of the interior side of a stone foundaton. Water has to go somewhere and better for it to enter the cellar and flow out through a drain or be pumped out from a sump than to build up pressure on the foundations outside.

I did have shotcrete sprayed on my own walls and it has held up very well for 10+ years. It's porous enough to weep moisture when necessary, but reinforced the walls very well.

Your best course would probably be to consult with an old house expert, stone mason, or structural engineer (the last if you're concerned about the general health of the foundation). Many masons have very little knowledge about or experience with stone as opposed to brick, block, chimneys, etc. A real stone mason ought to be able to evaluate your particular situation and give good advice. You might also want to see if gunite/shotcrete spraying is available and see what that contractor has to say.


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RE: Stone foundation

Hi mainegrower,
Again, thank you very very much for taking such an honest good faith interest in my problem!! I really mean that!! Most of the time on these blogs I find that some people just want to show you how smart they are rather than help!
Anyway, I attached below a link that "SHOULD" show you a picture of an interior wall of an old fieldstone foundation. This picture is almost exactly the way certain portions of my basement looks like right now!
I hope you can open it?

http://img259.imageshack.us/img259/7230/003gd.jpg

I do believe it is made up of mostly large granite stone blocks with smaller granite stone fillers? The mortar used on the inside is whitish and powdery now. So I'm almost positive it is some kind of lime mortar??
This area of eastern Mass, especially the city of Quincy next door. Produced very much granite back in the day. In fact Quincy still has the old quarry pits.

Anyway, sorry to bore you. Please let me know if you were able to open that link and view the picture? If so, please reply accordingly. I'm pretty sure I'll need some type of lime based mortar...I just don't know what type of aggregate mix(I.E. Recipe)to use and how?

Thanks Again..........

Here is a link that might be useful: http://img259.imageshack.us/img259/7230/003gd.jpg


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RE: Stone foundation

Blakk

Our old house in in a different part of the country, but the "recipe" for ours is: 2 buckets sand, 1 bucket masons lime, 1/2 bucket of portland. Hope this gives you a good starting point.


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RE: Stone foundation

Blakk: Not sure if you received my email yesterday, so a quick summary:

Wall in photo looks just like my cellar, right down to the old iron pipe.

This is what's called a rubble wall around here. Builders dug a trench and filled it with whatever stone was available - no mortar at the lowest level, then mortared in various size stones with or without some sort of form on the interior side. Once the exterior grade was reached, dressed stone blocks or brick was used to level off the foundation and bring it above grade level.

The most important maintainence is to make sure water stays diverted away from the foundation as much as possible. Gravity cellar drains fed by a perimeter gutter system were/are very common. No attempt was made to waterproof the whole thing.

Impossible to tell from the picture, but if your stones are also largely angular in shape, they are most likely granite or other very hard igneous rock. No worries about any sort of mortar doing damage because it's stronger than the rock itself.

I still think you will benefit from consulting with a mason or someone else knowledgeable about old house foundations. If yours is in as good shape as the one in the photo, little work would seem to be needed.


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RE: Stone foundation

Hi Mainegrower,

Yes I did receive your email, and please accept my apologies for the late reply?
Thanks again for some great insight and advice!
I must say that, I am surprised to hear that based on the picture I sent...You think my wall
is not in bad shape at all? I bought this house apprx. 16 years ago, and at the time the home
inspector told me, that the front portion of the basement wall hand to be re-pointed right away. I guess not
so much Huh?
FYI: My house sits at the top of a fairly steep hill so I don't get water in the basement ever.
If you could imagine it in your head? The front part of the foundation is almost completely buried underground,
then it tapers out almost evenly from the front to the back. So the rear portion of the foundation is completely above ground.
The problem area is the buried portion up front!

Thanks again and take care......

PS: I originally received this message at my personal email and replied there. The reply was sent back due to some error? So I just copied it and replied here....

Rob


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RE: Stone foundation

Rob,

Glad you got the email - email address has changed, so your reply did not get to me.

The wall in the picture still looks good to me, but may be misleading since two-dimensional pictures can't convey an accurate picture of a three-d object.

It's unlikely that the inspector would have made repointing a priority for no reason, so once again I'd suggest a mason or old house guru for consultation.

The fact that you never get water in the cellar (I'm envious) suggests a very well constructed foundation and close attention to drainage on the outside.


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RE: Stone foundation

So, just so I get this straight, from what I'm reading here and on other sites:

a. don't use quickcrete or similar types of concrete
b. a mix with lime is best so it doesn't cause rocks to shift/move such as 2 buckets sand, 1 bucket masons lime, 1/2 bucket of portland

Now, can I use the above recipe thinned just enough to spray through a hopper with a compressor? I need to do my entire foundation (rodents, water and cold air all love to enter my basement) and doing it by hand seems way to overwhelming. I could spray it though pretty easily.


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RE: Stone foundation

Thinning any mortar or concrete with more water results in a mixture with vastly reduced strength. You might be able to spray it, but it will likely neither stick to the wall nor last more than a short time.

Sealing the interior of a stone foundation with a sprayed on coating is not really a DIY job. Shotcrete and gunite are both very dry mixtures specifically designed for spray application. Both rely on a skilled operator with specialized very high pressure spray equipment.

There are various mortar recipes for use in tuck pointing, but any foundation so precarious that even Quikcrete will "cause rocks to shift/move" has problems much more serious than any mortar will solve.


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RE: Stone foundation

House was built in 1895-1898?,has been added to over the century. The house faces eastward on a hillside and the slope descends westward down hill. The surface water from rain and snow that drains from the yard, driveway, and street run downhill toward the foundation(crawlspace walls)at an inncorrect grading, home has at parts a deterorating foundation, and at parts water that drains from the roof is deposited next to the home's foundation from leaky gutter joints and improper grade where downspouts and splashblocks are. The grading is backwards on the east, west and north sides of the foundation with a slope of an 1" or less per foot towards the foundation.

The previous owner who remodeled the house and yard, built a massive driveway only 10 ft from the front and oldest part of the home where the crawl space foundation of rock and deterorating mortar is, the driveway slopes towards the home, and to make thing worse there are no swales in the yard, no driange for driveway, and no drainage around the footings of the crawl space walls.

The crawlspace foundations exist in 3 sections,the oldest and origional is a 16' x 30' limestone cut block wall foundation with deteroriating mortar, inside this part of the crawlspace was an old dumping ground with a large center rock mortar column supporting the main timber beam to the wooden floor framing. I can see daylight through the holes in the walls where the mortar has complete deteroriated, and water seepage throught the eastern wall that runs down hill damping soil under the home. I can see where mold, fungus, and rot are at the beginnings of invading the houses wooden beam andfloor framing and structure.

The second section of the crawl space foundation is 8.6 ' x 17' concrete blocks and extended the southern side of the house. This is were the plumbing is, and the furnace is above this section with air ducts running under the floors through the first and second sections of the crawl space ceilings. Inside here the ground is damp and muddy as well I can see tree roots from large invasie ailanthus altissima trees 10 ft south of exteroir crawl space foundation. I can see eflorescence, white crusts on the bottom foot of the eastern and southern concrete block walls, and it is the worst in the southeast corner where an outside downspout from the roof is overload with runoff from the the roof. I think the gutters and downspouts are not properly installed to mannage the roof runoff effectively, because too much water is direct to this single (likely 1/3 to 1/2 of roof runoff) downspout from various parts of the roof.

The third section is of the crawl space is a 14' x 14' wooden wing extended onto the western side of home, the backend, this part is only about 20 yrs old. There are no foundations or footing at all, the wing is on concrete/wooden columns with plywood walls for the crawl space. nothing but wood walls and earth floor with vinyl siding on the exterior. Seems like an invitation for termites, carpenter ants, fungus, mold, rot.

The primary problem is the moisture, dampness, and water pooling in the crawl space which is causing many more problems. So before i can even think of drying out, cleaning out, cleaning up, sealing , insulating, ect. the crawl space, i need to address the water entery.

Between, digging up the yard and installing french drains along the footing of the driveway and crawl space foundations, cleaning, repairing, the foundations, releveling the yard with proper grading along the foundation and adding swales in the yard, adding extra downspouts and gutters were needed, and directing the downspouts into drain pipes directing the runoff away from the foundation, and other unthought of possibilities, i am feeling a bit overhelmed with the scope of the problems. WHAT IS THE BEST ORDER DEAL WITH THESE MULTIPLE WATER ENTERY PROBLEMS IN THE CRAWL SPACE?


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RE: Stone foundation

As others have experienced, my recently-purchased, 19th century farmhouse has a stone foundation in need of repair. I'm chatty, so grab a snack and sit back for some light reading. ;)

Of the 3 basement rooms, the east room is not parged, and the floor gets wet after it rains.

The thing is, we accidentally discovered the south walls are hollow.

Yes.

Hollow.

So far, we've repaired an approx. 3' x 4' area of hollow, interior foundation wall that we could easily access. We knew there'd be more.

(I agree that parging only serves to hide problems.)

Sure, the mortar is nothing more than sand, in much of the south walls and the west corners. But when we started pulling away the loose stones, we found huge voids within the foundation.

Using stones and cement/mortar, we repaired the voids as best we could. We were feeling pretty proud of ourselves, for finding the exterior sources of the water problems, correcting them, and then fixing the foundation voids.) (When we first moved-in, I spent about 100 hrs in the one, non-parged room in the basement, brushing the surface and pointing every little gap.) We also painstakingly went around the above-ground exterior foundation, and filled-in any obvious gaps, and redirected downspouts and other water purge pipes. (As renovations continue, a new roof and gutters will be installed appropriately.)

But here's what happened (and why my urgency to get this solidified ASAP)... I like my music and movies. I'm very hard on subwoofers. The last one was 400W, and began deteriorating a few months ago. I lived without one due to the numerous renovation projects going on in the house. (We've lightened the house substantially, I suspect, by removing all the heavy, heavy plaster & lathe - double layers, in places - to lightweight drywall, as we reconfigured everything.)

So, as a kind of treat, once the home theatre was able to be set-up again, my husband bought a bigger, better, badder subwoofer for me. I now have 650W of goodness at my disposal. Yippee!

But, as always in life, there are pros and cons to everything.

The thing is, the west basement room has yet to be addressed, and sits directly under the new sub. After extended play at delicious levels, I went to the basement...just to see if there were any repercussions (pardon the pun). Frighteningly, there was some evidence of surface degradation. i.e. There was some sand/mortar, parge, and some small rocks on the floor. As best I can tell, the thumping bass dislodged them (although I can't be 100% sure, as I didn't check first, and we had similar results elsewhere, when doing the main floor flooring).

Again, here's the thing...

I took my super-skinny pointing tool and poked various spots on the interior foundation wall under the subwoofer. When it easily went all the way in, I tried a longer length of stiff electrical wiring. It went in a foot, with ease.

A little freaked out, I went back to the middle basement room, where we'd repaired part of the wall. The untouched areas are parged, so it's not easy to find gaps to test. Then, just under the repaired area, I tried a space just big enough for the pointing tool, and it wet all the way in.

Our exterior, south wall of the house is covered in ivy. A neighbour informed us that, a few years ago, the (brick) wall collapsed inward. The repairs are only evident once the ivy dies away in winter. However, it doesn't appear the foundation collapsed, or was affected by the collapse. But with that parge and paint, who knows?

Soooooo... As I get down and dirty with more urgency in wire brushing and re-pointing, any expert thoughts, recommendations, pro tips? (And no...the foundation needs to be strong enough to handle the subwoofer, as that bad boy's not going anywhere.) ;)

Until now, I'd always kind of felt a little invincible, in that the house has faced countless storms and even some minor earthquakes over its century+ life. There even used to be a railroad across our front lawn, not 75' from the front porch. Surely, a little truck rumbling, thunderstorm, or occasional subwoofer use couldn't hurt it. Now, I'm nervous. :O


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RE: Stone foundation

What a great pity that you had to, or chose to, take out and not replace the plaster and lath of the walls. Their "weight" was not a factor as long as your sills were fine. It's a luxury material that adds a lot to the experience of quality in a building

The accoustics of plaster and lath and a gonzo subwoofer are amazing. Almost tactile, really.

It's extremely unlikely the subwoofer is destroying or altering your foundation.

(Though you can damage weakened wall plaster with acoustic equipment.)

However, you might do well to do some more research on how to manage (field?) stone laid-up foundations and the maintenance they may require, or not. One important issue is using modern Portland-type cements to point or parge softer old-fashioned mortars. Another is pulling out pieces to fix voids and divots behind and in the wall itself.

The most critical foundation wall maintenance issue, occurs on your roof and soffits and on the surface of soil just beyond the foundation (making sure it continues to slope away from the house, and doesn't change over time) and NOT in the basement. If you don't have proper gutters, don't wait for a future roof overhaul to install some working ones soon- even the ugly K-type ones are better for the structure than none.

Thefoundation wall's rocks piled up, and stuck together (or not, depending on your climate, soils and the skill of the original stone worker) have mostly long-since arranged themselves in an equipoised, sturdy way (absent the counter-force of misdirected water cascading down from the roof - see gutters, above). The mortar is probably mostly for keeping critters out than anything else. Don't mess with success, in the name of a tidyness judged in comparison to a modern poured foundation wall.

This is a general recommendation. Your house may have been slapped together by inexperinced workmen. But a house with a full basement was not a casual undertaking in the days before motorized diggers, so it's likely to have been done by people who knew what they were about. Where fieldstone is more commonly a problem is on not-as-deep foundations where sheds and the attachments were, over time, included within the house itself, despite having only minimal foundations, not going deep enough to be immune from heaving and shifting.

Most stone foundations are extremely uneven below grade because the rocks, while chosen or cut to make a relatively smooth plane within the basment just stick out in natural ways on the outside. Excess water over many years (see gutters, above) can gradually wash out not fully-compacted backfill around the outside in certain soil types, even below grade creating the impression of voids.

Get yourself out of the basement and up on a ladder. (see gutters, above.) Hanging ordinary half-round galvanized is something two people on two ladders can easily learn to do. The (and less desirable in a style sense) site-formed K-style usually takes a special machine. It may be a rentable machine.

L.


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RE: Stone foundation

The concrete gets powdery because of prologned exposure to moisture. the salt in the concrete gets leached out and what remains behind is a chalk like substance.

the first thing to do is solve the drainage problem first as this may cause bigger problems down the road such as erosion and eventually foundation settlement. you can do this by proper grading of the land around the foundation as well as installing french drains that direct water away from it.

next, you can then reapply mortar or concrete. for waterproofing, you can use polyurethane.

Here is a link that might be useful: Foundation Repair Options


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RE: Stone foundation

Our house is an 1850-1860 (not sure of exact age) with a similar type foundation. When we bought the house 4 years ago we hired a foundation inspector separate from our regular inspector. Our foundation expert is in his 70's and besides being a structural engineer has 50 years in the business. He said we wasted a good $75 hiring him because the foundation wasn't going anywhere. Being a natural material, stone foundations are supposed to weep a little and there is even shallow trench and pipe in our basement to carry the water out. It is not a lot of water but a little when it rains a lot. We only use our basement for storage and put our things on pallets. Our house is not airtight and generally that is a good thing.


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