Stone foundations

[bigmish]

In his book Timber Frame Construction, Jack Sobon describes a stone foundation that can be used for timber frame buildings. I left me with a great many questions:
1.   Is the foundation set in the ground at all, or does it sit on top? If in the ground, how deep?
2.   Am I understanding correctly that there is no mortar between the stones?
3.   How large a building could this support? Could it be used for say a two story 25x40 timber frame building?
4.   What are the disadvantage of a stone foundation? How long will it really last? Are their inspection issues?
5.   Are there any recourses (books, websites) that address the techniques of building a stone foundation in greater depth?

Thanks, Mischa

[beenthere]

Arky has some pics in his gallery of stone foundations, (or are they stone levelers  ??? )





Probably depends on the soil under the stones. I'd think sitting on bedrock or below frostline, if mine. Many a barn has been built on stone foundations, so it can be done. Where are you located?  Probably there are code issues that need to be considered.

West of where I live is the Talieson complex of Frank Lloyd Wright, and the home he built (had built) sits on limestone 'foundations' that just sit on top of the clay-soil ground. Temporary at best for this area, and considerable settling and moving which has made repairing and restoring the home itself VERY expensive.  For a look at some pics, I've included this site, the  Taliesin East at Spring Green, WI

[slowzuki]

Foundation design always depends on the soil.  Modern codes don't like foundations that move so they will want you below the frost line and on material that can support the weight you are putting on it.

Our building rests on a rubble trench foundation which is a trench lined with filter fabric and filled with compacted crushed rock and drain tile.  It hasn't moved and keeps things very dry.

[Jim_Rogers]

slowzuki:
What building is that?

Jim Rogers

[slowzuki]

slowzuki:
What building is that?

Jim Rogers

From a little while ago, the roof is nearly all done now:


I'm cheating, its built using socket systems connectors since I haven't any training traditional joinery and the building inspector wanted to see engineering documents.

Not much of the bracing is installed in the building yet, we have a 50+ psf ground snow load which translates to about a 40 psf roof snow load on a 30 deg pitch with our codes.

The building is 33 x 65 and 24 ft tall at the peak, it will have an apartment at one end and a shop as the rest.  It has been a struggle and we have met resistance from almost every person in the project, the building inspector, engineers, contractors and even bystanders.

The building inspector wouldn't approve our foundation without an engineer, the first engineer wouldn't seal our frost protected / rubble trench design because he thought "rats" would eat all the foam and the building would shift.

The next engineer decided the frost protected part was fine but our rubble trench was given nearly no bearing capacity allowance and turned our footing with minimal reinforcment into a grade beam / spread footing with so much steel and hoop ties it was ridiculous.  I calc'ed it myself later with the ACI standards and with full snow load we could escavate an 8 ft wide portion below the "grade beam" centred at a post and it would span it fine.

As it happened we didn't get as good of start as hoped so our slab lived through the winter here just fine despite getting barely any snow, which completely negated our frost protected design, and guess what, came through fine.  Our rubble trench and under slab drainage kept it dry enough to prevent any frost heaves.

[JimBuis]

My Dad's house was built in about 1875 in Illinois on a limestone foundation.  The stone is what I would describe as slabs, flat rocks about 4 inches thick and about 15 to 25 inches in the other dimensions, very much irregular in shape, no mortar.  The stone goes below the frost line. The house is absolutely solid and shows no signs of settling.  The place is a stick built house.

Jim

[Don P]

Most of us don't have easy access to Jim's quality of rocks, boy I wish I did. Ours locally would fall under rubblestone foundation. They need to be 16" thick minimum. That would be a 12" thick x 24" wide footing  below 24" frostline here. Mortar would be required, M or S. Most of our old dry laid rock foundations have shifted around here. I've worked on 2 that the rocks shifted enough to to spit out of a corner, leaving it hanging and sagging. On one dry laid basement wall the critters nesting behind the wall had loosened and removed enough of the bank behind the wall that it bowed back into the slope. That took some head scratching, at first it seemed to defy gravity and common sense.

My wife and I have been making a stone woodshed foundation / retaining wall this summer. Its about 10' long 4'deep and 4'tall, solid rock filled. We mix a pea gravel concrete and stack the faces dry. We then fill behind the rock forcing concrete in and then stone fill the core with concrete and ugly rocks. I'll grout bag the front if it needs it.  I've used a similar technique under a log cabin. We formed a plywood wall under the house about 18" in. We then laid up a recessed joint mortared stone wall and filled back to the plywood with concrete.

[SwampDonkey]

The foundation in the main part of my house is field stone and mortar. It's held up better than 40 year old cement.  :



I've found old foundations on abandoned farms without mortar.

[bigmish]

To all interested in this topic, I found this in researching: http://weblife.org/cob/cob_018.html

[MSU_Keith]

Hey Slowzuki, how about some more details about your foundation:
- Are rubble trenchs just under your three lines of posts or around paremeter or both?
- How deep and what size/type of rubble?
- How high is your water table?
- Can you drain down slope or do you drain to a cistern?

I have some land with a high water table and we considering this foundation type.  Inquiring minds want to know. :P

[Don P]

We had a gravel foundation under a precast foundation last year. I think the builder guide download at Superior Walls site  has some specs as does the '03 and '06 ICC codebook.

I think SD's pic is of the old lime mortar. We'll run into it in older, usually pre turn of the century buildings. It was not a modern portland cement mortar, remember the Roman's cement was lost to us until about 1825. The lime mortar is softer and has the ability to kind of "heal" if the building moves. Someone was describing the demise of old barns to me one time and made the comment that moving the animals out was the beginning of the end for alot of the lime mortared stone barns. The livestock's respiration and moisture is what kept the old mortar hydrated. I'm not sure if it's that or the farmer's attentions turning elsewhere but it does sound plausible. Those mortars turn back to stone over a scale of centuries. If an older brick building is built with this type of mortar, never use cement mortar in a repair. The harder cement will support the old brick very well, so much so that as the rest of the building moves on the softer mortar the stress will concentrate on the repair and crush the bricks.

By the 20th century most people had switched to cement mortar because of its increased strength. It also sets much faster, getting up to full strength at about 40 years.  Bricks were by then made in much more controlled conditions and are far stronger than the older brick. I haven't seen too much residential pre WWII concrete that looked like much, portland was still expensive and alot of the aggregate I've seen was round from the river, it didn't hold together as well as sharp crushed stone and sand. The cement itself was also undergoing changes in the early period. Those changes came at different times to different people. Dad remembers the lime pit in the yard on some jobs

Alot of older houses here are on dry laid foundations. I repointed a mud laid stone chimney well over 25' tall a few years ago. I don't think either is a good idea for a residence, it was done out of necessity. I do not believe that dry laid walls extend the life of the sill or the structure.

The building code does address cement mortared stone foundation walls; Stone ashlar masonry like Jim described but mortared is allowed to bear 720 psi if in granite, 450 psi in limestone or marble and 360 psi in sandstone or cast stone. Rubblestone is allowed to bear 120 psi. I suspect lime mortars are about 1/3 of that.

Cement is not environmentally friendly... at all. I feel I'm also leaving a legacy of 50 yard pours that someone sometime will have to remove  :-\

[SwampDonkey]

The old foundation withstood an earth quake in the 20's. ;D

[Don P]

And has likely reknitted some  ;). I'm not knocking it. Alot of times we try to build something as strong as we are able to now, you can quite often look back and ask "What's strong enough?". Look at the Mayan dry stonework, I'd happily build a castle on a foundation like that. My inspector would issue them a stop work till they got an engineer  :D.

[SwampDonkey]

Ok, off on a tangent...  ;D

Engineers?? Who needs em? ;D My mother's uncle was a foreman on the railroad and he was also a bit of a 'make fun'. When my uncle told him (his uncle) of the rail they surveyed for and laid out in northern Quebec around Baie Comeau his uncle would tell him 'we never needed no survey equipment, we went by eye'. :D  :

Ok...maybe way out there with no connection....  :D :D

Reminds me of the fellow who said he never needed a compass in the woods, he always walks in straight lines. I was thinking yeah, in a straight line across the property boundary trees onto the next lot after the big spruce. I bet you could see the line trees in the pulp pile with red paint.  What line? where?  :

[Furby]

Here's another twist, if you have homeowner's insurance, your rate is much higher if you have a "stone" foundation compared to a "regular" concrete foundation.
Least that's what I found after talking with many insurance companies around here.

[SwampDonkey]

That must be why my home owners insurance went from $650 to $420 this year. I ain't say'n nut'n. ;D  ;)

[Furby]

 :D :D :D

[SwampDonkey]

I also wasn't home and the tax assessor left a package for me to fill out the description of the house. All, I can say is I expect the fire marshall, the Sherriff and the building inspector to appear at the door any day now to condemn the place and put me in a welfare home. :D

[slowzuki]

Hi Keith,

-The rubble trenches are under the perimeter and the centre line.
-They all slow downhill and we are fortunate they can drain to grade.
-They are 3-4 ft deep (sloped) from the orginal flat area we cut, so with the crown of the fill and the footing/gradebeam the bottoms are 5-6 ft below the floor, or 4.5-5.5 feet below grade.
-The rubble is 3/4 and larger (goes to about 1.5") clean crush ie no fines. Although we ran out where we had to escavate some topsoil someone had burried about 15 years ago when cleaning a fenceline.  There we used 3/4-2" pit rock (rounded rocks that don't compact or rather are near full compaction from the start)
-Our water table turned out to be low except a leak from the burried fence line trickles into our foundation.  The neighbours foundation built in similar soil hit 3 springs and had to be pumped the entire time until loads of crush and lots of drain was put in.  They had a complete mess while building.

I would check what type of land it is, we have a clay till here that is poorly drained but is generaly hardpacked and will support a lot of weight.  In other areas near here there are really wet soils that can't support much weight such as the clays that have enough sand to get water all through them.  I would want a rubble trench to be in the ground for a while to start its work before loading it.

Hey Slowzuki, how about some more details about your foundation:
- Are rubble trenchs just under your three lines of posts or around paremeter or both?
- How deep and what size/type of rubble?
- How high is your water table?
- Can you drain down slope or do you drain to a cistern?

I have some land with a high water table and we considering this foundation type.  Inquiring minds want to know. :P

[Full Skip]

Long time lurker, first time poster.

Here is a stone foundation I'm doing at the moment.  I don't know why there is such a fuss over these in this country.  Places in Europe like Holland still use laid stone on new contruction and their construction codes are very stringent.  Typically the Dutch drive pilings under the stone because the subsoil is very poor there, but it's still laid stone - and you don't see a lot of brickwork that needs to be done due to settling either.

Europe has thousands of examples of these foundations.  I visited a Dutch town hall built in the 1200's that was done on this sort of foundation.  It leans a bit, but it is still standing, and it's still the town hall.

[beenthere]

Full Skip
Welcome to the forum.
Nice looking stone work there. Laid with or without mortar ?

Maybe there is a fuss here because of BI (building inspector) ignorance, on the part of the 'fusser', or instead the amatuers laying stone for their first time (like the locals hired by Frank Lloyd Wright for additions on his own home, who just started on the top of the ground  ).  These things can turn others away from a perfectly good, tried and true foundation system.  PS No intent to disagree with anything said in this thread. 

I'm sure there are thousands of examples of stone foundations all around here too, like in Europe. Many barns still standing on them.
An engineer condemned our town hall (old brick schoolhouse) because it had a stone foundation. He was very ignorant, but he didn't have such things in his engineering text book, I suspect. Or was it that he was hired by the group that wanted a new town hall?  Hmmm?  The stone foundation was over 100 years old, and had survived a fire in the 20's, after which they built a brick schoolhouse on the same foundation. There wasn't a crack between any of the bricks, yet they condemned the foundation as unsafe for humans.  >:(

[slowzuki]

The problem with us engineers is insurance liability.  If he looked at it, then an earthquake knocked her down killing a person inside the building, he would be sued for everything he owned and never work as an engineer again.  All because he has no way to calculate earthquake loads on stone foundations.

[beenthere]

I re-read my comment about the engineer and mine (ignorant) was maybe a bit harsh. I understand their dillema with the liability thing, and it is unfortunate that our sue-happy society and the backlash it creates (so many using it as an excuse not to do what is logical) will haunt us into the future, IMO.
Much easier to turn something down (home sawn lumber is but a good example) and accept a no-risk path.  There is a part of our society bent on making us fear all things, good and bad. And if something happens in the way of bad luck, then someone should have to pay. (this is probably too harsh too  ).

[TW]

I have seen some references to dry laid foundations in Europe so I want to comment.

They made those foundations here in the old days. We have a hard kind of granite here so there are no flat slabs that can be stacked easily. They dug a trench at least one meter deep and filled with boulders and built the foundation on that. The foundation was seldom higher than one meter above ground.
Those ones that stand on natural gravel usually lasts quite well and those that stand on blue clay have crumbled. The old loghouses could withstand quite much settling and still stay in one piece.
I would never build a new stone foundation without concrete below ground.

This is just my oppinion. It may be a different situation in the "tropics" where the ground does not even freeze.

[Full Skip]

My guess is that the stone foundations on new construction in Europe are probably limited to parts of France, Belgium and Holland where you have a soil that is basically this North Sea type of sand after you dig down and offers good bearing capacity.  Then, it's definitely a sort of hybrid foundation where they're pounding in these pilings below the huge, nicely quaried stone that comes from Germany, Norway, Sweden... wherever they can get a nice granite or similar rock.  Like you mention, the foundations are not that high.

I just bring it up because I see something like that as being a possibility over here.  Brick and block aren't all that good at standing up to earthquakes either, but they're widely used.  I would think that stone could actully perform better in most cases if it were done right or maybe if the foundation just had a few modifications.  As far as that goes, I think that brick and block win out simply because it's easier to bolt a sill plate on them.

In any case, a shed/barn and a dwelling are two different creatures.  All I know is that I plan on building a little getaway cottage in the next few years, and I plan on doing it on a stone foundation.  I'll just build it on some land here that doesn't have all the zoning requirements.

[bigmish]

Sounds like a concrete footing is a necessity for a house sized structure in colder area (I'm in upstate New York).

But I'm wondering, what about substituting a rubble trench for the footings, so to speak? That is to say, rubble trench up to ground level and then stone crawl space walls...

[slowzuki]

Bigmish,

That is basicly what we did.  Concrete can't take frost heaving any better than rocks, it will crack and break up.  You need 3 things for frost heave:
-freezing temps
-frost susceptible soil
-moisture/water

Railways built a high bed of non-frost susceptible soil to solve it.  Frost protected designs use insulation to prevent freezing of the soil.  Some other designs put a layer of vapour barrier and a porous layer before packing original soils back on top in layers, this is a moisture managed design.

BTW normally a building built in a bog won't heave, the water level in the soil is so high the ground doesn't freeze more than a few inches to a foot.

A rubble trench attacks two heave problems, it is a non frost susceptible material and it dries the ground out to help prevent heave in the soil around it.

[bigmish]

slowzuki, that's stone on the rubble in that photo? Looks like a poured slab. Or was this on a diffrent building?

[SwampDonkey]

We hauled field stone from several rock piles on the farm and built up a 4 foot layer of stone, with a layer of gravel on top, before pouring concrete. It was 20 years ago for a conset building. It's held up well and there has never been any heat in the building. It was just to store machinery out of the weather.

[slowzuki]

Sorry, in engineering terms stone is almost the same as unreinforced concrete.  Mine is indeed concrete.  Mine only really needed steel to fight the shrinkage cracking, but was speced by another engineer (not me, the building inspector wanted a structurals stamp) who did not recognize the performance of the rubble trench so it contains lots of steel.

slowzuki, that's stone on the rubble in that photo? Looks like a poured slab. Or was this on a diffrent building?

[MSU_Keith]

I'm considering a hybrid foundation:
- rubble trench topped with a poured concrete grade beam around parameter
- joists on top of grade beam creating crawl space
- poured concrete piers up to finished floor level for internal post supports

My thinking is this will save me money on poured concrete and parameter rubble trench will solve some water problems as mentioned.  Slowzuki: did you consider piers for your internal post support compared to rubble trench/grade beam down the center?

[slowzuki]

Keith, yes I did consider piers, but the escavator dug the trenches in about 1.5 hours instead of me having to sink piers.  I also considered piers to the trench but didn't have information on my bent spacing at the time of the foundation work. (Very bad idea by the way!)

The engineer I hired to stamp the drawings suggested piers all the way around but I wasn't at all keen on that.  I've tried sinking things in a line before for pole barns and it is darned hard to get square.

[Don P]

The masons are just about done on a stone retaining wall I thought was worth showing off. We call it a dry laid look, the mortar is held back from the faces wherever possible.

He did a nice job with the steps

One thing the present code doesn't address that I recall from dad's old book was bondstones. If I remember right it said that a stone needs to cross through the wall every 4square feet. Required or not its a good idea. Look at the third rock above the footing. 

I quizzed the mason and he's never had a request for a dry stack new foundation although he has repaired some. He pointed out that he has to bed anchor bolts 7 inches into the foundation nowadays and couldn't do that in a dry stack.

[SwampDonkey]

Looks really good to me. And that job is alot more work than one might think, no easy task.

[Raphael]

  That's a nice looking wall, we've done the same thing with the field stones facing our chimney.  Around here rocks are the number one agricultural product, always harvest a good crop every time you till.



I plan on dry laid stone for a number of accessory buildings but it won't make code for housing.  I've got tons of blasted ledge left over from setting my septic tank and pump chamber, plenty of rubble and stone to play with.  I thought of using some of the large rocks as a foundation on grade to display timberframes for sale on.

  The 'Alpaca shed' I plan on building in the field will have rubble trenches (sloping down to daylight) and oversize piers to handle a 100psf+ roof load.  Stone will get laid between the perimeter piers.

[SwampDonkey]

Nice work on the flu Raphael. I like that little stove to. Never seen one like that. Is it a pellet stove?

[bitternut]

Hey Raphael that is quite a substantial looking chimney. I see you have a stove just like mine. Well almost anyway, mine has black enamel trim not white.

Donkey that stove is a Petit Godin. I think they are made in France. They have a cast iron shaker grate, little ash pan and the top flips up also. You can burn coal or wood. Well what the heck, I will let Raphael tell you all about his.

Sure wish I had nice stone like that handy to use for projects.

[Raphael]

My Petit Godin was a gift from a customer or perhaps it was a bribe to take away misc. garage clutter.  :D
  Eventually it'll be my shop stove, it's very tight and has a significant mass of cast iron lining the firebox so once it get's hot it can really crank out the heat.  It functions best as a coal stove as the fire box is quite narrow, it'll hold a coal fire all night but wood small enough to fit the firebox burns up to fast or smothers.  It has a double flue arrangement, a small port directly opposite the stove pipe and a larger upper flue that drafts down through an additional iron element on the back of the stove.  In france it would be used as an apartment or parlor stove.
  Our chimney is wider than it needs to be on the first floor, mostly to get the thimble centered in the mass but also to add thermal mass and balance the stove that will be going there.  We have a restored 1860s 18" cylinder stove that stands nearly 7' to the top of the finial, the chimney won't look quite so large with that parked in front of it.

[SwampDonkey]

We have a restored 1860s 18" cylinder stove that stands nearly 7' to the top of the finial, the chimney won't look quite so large with that parked in front of it.

What you heat'n?  ;D

[Raphael]

We have a restored 1860s 18" cylinder stove that stands nearly 7' to the top of the finial, the chimney won't look quite so large with that parked in front of it.

What you heat'n?  ;D

~2000 square feet of house plus some outside air when the heat gets to high inside.  ;D

[scgargoyle]

I grew up in a c. 1790 center chimney cape near the shore in CT. The soil was sandy, and the foundation was dry laid granite, although there was some chinking above the ground to block the wind. The chimney stopped at the ground floor, and was supported by two stone piers, with solid logs between them. The rafters were just logs flattened on one surface (they still had a little bark on them) for the roofing boards. They were notched into each other and secured w/ a trenail. That house was straight and solid after 200 years! We had the clapboards replaced on the south side of the house, and underneath the house was planked w/ chestnut 32" wide, and over 20' long. The flooring was original random wide hardwoods, double planked, and old rope jammed in the seams. It was built and lived in by a whaling captain, and was a fascinating old house to grow up in!