Is a rubble trench foundation legal?
The architect Frank Loyd Wright invented and used “rubble trench” foundations in some of his buildings. Basically you dig a trench down to the frost line, lay a drain pipe in the bottom that slopes down and out to daylight, then fill the trench with gravel. There is no frost heave because there is no water in the trench – it runs out through the pipe. Wright came up with the idea after observing that railroad tracks are not affected by frost because they sit on a raised gravel bed.
I think it’s a great idea, and the few references that I found all praise how well it works. I’d like to use this system in my new house that will start construction next year.
My question is how will this fly with the building permit people – what do I need to convince them that this is a practical foundation? Should I hire an engineer to write up a formal approval, blueprints, etc?? Also, does anybody know of such foundations from practical experience?
BTW my future home is a modest 1,200 sqft retirement house, so it’s not the Taj Mahal or an office building.
Thanks,
PaulBen
Replies
sounds to me like frank designed his foundations just like he designed his roofs, they all leak! franks vision and sense of space was genius, i love just about every interior i have seen of his, but many of his ideas were not practical.
the tough part is anchoring the structure to the rubble foundation to meet dwelling codes/requirements
I have heard of pole barns and fences being built with a rubble type foundation with success. you have to have the right conditions (soil) for it to work properly, and it is probably not something an unlicensed person can design depending on where you are. it will probably be more cost effective to go with what is a standard accepted by your local building department for a small structure/dwelling, talk to them about it, they will probably give you a little handout on what is required for foundations in your area.
from an architecture standpoint, you would be wise to be influenced by Wright.
from an engineer/builder perspective, you would be wise to not follow his example too closely.
Superior Wall precast foundations use a gravel footing. Bob Vila seems to be sold on them, so that's good enough for me.
I have a fifteen year old addition on my own house that is built on a rubble trench. There is not any sign that this is at all different from the rest of the house. I was not sure how it would work at the time but was willing to experiment on my own house. It would use it for a customer in the right circumstances. My addition is built on a slab with the perimeter on a rubble trench.
As to the building inspector, the best way to find out what they will accept is to ask them. In our area a house under 1500 sq. ft. does not need a set of arch/eng stamped plans but the inspector can pretty much require what he wants unless you can convince him otherwise. Depends on the guy.
paul.... 1st , you have to define "rubble"....
crushed stone works great, if it's uniform, compaction will be minimal
rubble is not uniform and will require compaction...
gravel is gravel.. not rubble, not stone.. gravel works great , too.. but it requires much more compation.. all three perfom well as footings .. IF they are captured by the trench as a confinement ..
careful with the drainage.. it CAN carry enough fines and materials away to undermine the footing
Mike Smith Rhode Island : Design / Build / Repair / Restore
This is an interesting idea, but I imagine you'll get some resistance. What will you put on top of the rubble? A typical masonry (MasonARY?) foundation does more than hold up the house. It also gets things up out of the water and soil, gives you place to put insulation, and holds the house down in storms or earthquakes. A concrete or block foundation can be water-proofed to help keep the house dry. Basemants and crawl-spaces can come in handy. What's your climate like?
I think I remember reading about floating foundations in the far north. There, frost goes so deep, that home are built on a bed of gravel. The whole house may move slightly, but the gravel keeps things dry enough to minimize this.
Al Mollitor, Sharon MA
The answer to this is found in the code book. Yes, they can be legal, nothing wrong with them at all in most cases. I think everyone who builds anything ought to lay hands on the code book for their area. The new IRC particularly is quite user friendly. And it's not a bad thing to know the code better than your official does.Andy Engel, The Former Accidental Moderator
This is an interesting idea, but I imagine you'll get some resistance. What will you put on top of the rubble? A typical masonry (MasonARY?) foundation does more than hold up the house. It also gets things up out of the water and soil, gives you place to put insulation, and holds the house down in storms or earthquakes. A concrete or block foundation can be water-proofed to help keep the house dry. Basemants and crawl-spaces can come in handy. What's your climate like?
MojoMan
Per square foot, basements are the second most expensive part of the house (the first is the woman who lives in it - that's why you need to temporarily get rid of her when you start planning and building; I estimate that I've saved $150,000 by not having a wife at the moment).
And what does a basement get you, - a place to store 6 bottles of wine and a water heater? I live in central PA. My plan is to dig a rubble trench perimeter, then pour a slab. The money saved by not having a basement will buy insane amounts of insulation, a new car, vacations, expensive women, etc. etc.
PaulBen
I am modestly in favor of using a trench foundation with rubble in somesituations. Most of the old jhouses here haver some version of this so I can see the good and the bad after a hundred years or so.
But you last bit of info to complete the plan changes all this. you will be placing the preimeter of your slab on one type of footing andf the balance through the middle on another type of soil. I believe this will create a diaphraghm effect for you, with strong possibility of both uplift and settleing actions fighting with one another, cracking the slab and parlaying into joint cracks in the drywall finish. How bad it is depends on the kind of soils and how much moisture they hold or not.
If you want a slab foundation, you can do a monolithic pour with compacted stone and gravel for 12-18" of base and foam thermal barrier..
Excellence is its own reward!
Piffin,
What a great bit of information (the diaphram effect on a slab). I'm amazed how much you guys know, and that's from someone who has been building stuff for 40 years.
PaulBen
Here are my thoughts, for whatever they are worth (if anything). A friend of mine works for Superior walls, and believe me when I say I have heard the entire sales pitch. I think it is a good system, and a construction company I worked for in the past did a couple of houses using the Superior Wall basement. It is basically a system of factory cast 5000 PSI concrete wall sections that are custom made per the customer's foundation plans. The precast walls sit only on gravel (washed & compacted 3/8" stone), and the width of the bottom of the walls is about 10". Each panel is about 9' tall and about 10 - 16 feet long depending what the individual foundation requires. The wall sections are bolted together with some kind of sealer between.
Here is the rub though: These wall systems are rigid. For a masonry foundation at least the first several courses gets their rigidity from the concrete spread footing below. So, with a precast or maybe cast in place foundations, the idea of a rubble trench footing is fine. For a masonry foundation that is not inherently rigid, I think it's a bad idea. You did not say what kind of foundation you were doing, so not sure if this pertains... Really though, I can't imagine why anyone would want to do this unless it is a precast foundation or perhaps a monolithic slab, which really just has the footing integral to the slab.
Either way, if you wanted to get something like that inspected, I bet the inspector would require an engineer's letter approving the installation method. BTW - Superior walls come with the engineer letter(s).
Re code requirements, I may be wrong, but I blieve the only mention of gravel foundations in our NC code is for PT wood foundations. As far as that is concerned, and I may take some heat for saying it, but I'm not into temporary houses... Or at least I can't see how it would be a long term soution in my wet part of the country. Personally, I'm into concrete footings with rebar.
Matt
Edited 12/23/2003 6:43:34 AM ET by DIRISHINME
You're in an area when block foundations are the rule, aren't you? If you guys did poured foundations, well, it's amazing the rigidity that a $100 worth of rebar buys. However, wouldn't pouring the slab between the walls would brace the bottom of the foundation? Add a couple of pilasters in the walls (Seems to me we did them every ten feet or so in NJ), or grout and rebar some cores, and I think you'd overcome the rigidity issues. For the record, I've never done a rubble trench, but I live next door to a couple of houses that have Superior Wall foundations. And then there's FLW's Imperial Hotel, which rode out at least one major quake that leveled much that surrounded it. I'm intrigued by them as a way to save time and money without sacrificing any integrity. I don't know how one would handle a step in the footing, however.Andy Engel, The Former Accidental Moderator
Yes, here, block foundations are the rule, as are crawl spaces, undoubtedly because we only need to set the bottom of our footers 12" below grade. Basements are poured concrete with a few block and precast. Probably 15% of houses get basements. 10 years ago, when I moved here from VA, basements were made of block. When I asked, I was told - basements? Oh no, we don't build basements, because they leak! My response: Well yea, look how you build them!!! That said, I'll bet anyeone $1000, that if I call any of the regular poured conccrete subs or masons in our area, and said - hey, "I want to build a foundation on gravel footers" that they would *never* return my call. They might even just hang up on me - straight out... Having ideas, good or not, don't mean squat, unless you can get a sub to do it - or do it yourself.
I didn't quite get your point about the "FLW's Imperial Hotel ", since I'm not familiar with that project, but it must not have been that great if they demolished it. Was that a rubble foundation?Matt
>> I didn't quite get your point about the "FLW's Imperial Hotel ", since I'm not familiar with
>> that project, but it must not have been that great if they demolished it.
He said the hotel survived the earthquake, while many of the buildings around it were demolished.
http://nisee.berkeley.edu/kanto/kanto.html
From the article you referenced, one of the 2 major reasons the building was eventually demolished was because the foundation was slowly sinking into the earth and was not repairable. The other reason was that it was a low structure occupying some high priced real estate. Not sure though what this building has to do with this thread, other than the FLW reference, as the building apparently did not have a gravel foundation.
Further, from another thread I gather that the guy who started this thread really wants to do a monolithic pour slab so actually the whole thing is bogus.Matt
Sorry. Just trying to be helpful. You said you weren't familiar with the project, so I posted a link to more information.
No apology necessary. Thanks for the link. Just trying to puzzle togheher what this particular FLW project had to do with this thread. Yea - I'm kinda gruff. Don't mind me. Lots of skills, but low on people skills...
Matt
If you follow Breaktime for long, you will soon realize that following logically is not a prerequisite for a response to a thread...
Been here since roughly '97...Matt
"I'm kinda gruff"
Its D Irish in ya.
CurlyHand Hewn Restorations Inc.
Restoring the past for the future.
Further, from another thread I gather that the guy who started this thread really wants to do a monolithic pour slab so actually the whole thing is bogus.
Matt
I'm the guy, and I want a rubble trench foundation because it's effective and cheap. But this group has pointed me to the ultimate foundation - frost protected shallow foundation. LOL, why would anyone <not> want to build with this? It's effective, fast and economical. I just can't understand mentalities that want full basements. I guess it's a question of having too much money.
BTW I'm reading Frank Loyd Wrights book "The Natural House". He <hated> basements and attics.
Paul
Paul:
The thing is that if you just had used the word "slab" in your initial question, we would have gotten to the frost protected slab a lot quicker... Have a good HollidayMatt
I've been lurking here and enjoying the discussion. I'm familiar with the rubble trench theory and it seems pretty sound to me. I'm also familiar with the frost protected shallow foundation idea. Someone else here gave me this link a few months ago:
http://www.cs.arizona.edu/people/jcropper/desguide.html
I'll agree that in cold climates a whole lot of energy, time and money goes into a part of the house (basement and/or footing) that doesn't serve any other useful purpose. Anything that can successfully get away from that is a plus in my book.
One of the often overlooked factors in the physics of footings is that the weight of the concrete in the footing & wall system can exceed the weight of all the rest of the house combined, which seems kind of silly since much of the purpose of having it in the first place is to distribute weight.
Happy holidays
Thanks for bringing in that PDF document. It looks to be good but at 54 pages, it is a slow download. I'll save it for later. Had to get to page seven just to get past the governmentese to the table of contents.
But don't be too quick to dispose footings as silly. That conclusion depends on the type of underlying soils and the amt of water traveling through it that support whatever type of foundation is chosen..
Excellence is its own reward!
I hear you regarding finding a sub who'll do work a different way. That's how it's been everywhere I've ever worked. And it does make some sense; Changes to any technology that's worked for years should generally be met with skepitcism. Personally though, I find it quite frustrating when they're met be what I call willful ignorance (No, I'm not calling you willfully ignorant, not many of those types frequent this board).
As to what eventually sunk the Imperial Hotel, I don't know. I do know that its rubble trench foundation survived one big shake. I also know the mechanics of footings, whose job mainly is to spread the load of a building out to a point where the psf load is less than the underlying ground's bearing ability. That can be done as well with compacted gravel as with concrete. That system works pretty well on say, the Interstate Highway System, or on the runways at O'Hare. The foundation's stiffness can come from the walls just as well as from the footings. In fact, basement walls have to be stiff to resist backfill pressure anyway. Andy Engel, The Former Accidental Moderator
I hear ya. But from reading the link Uncle D posted I did not get the impression that the Imperial Hotel had gravel footings. Rather a network of small pilings.
No matter, since the guy who started this thread actually wants to do a monolithic pour slab which is fine for a gravel base.
Re change, I'm all for it. But in a prudent way so that there are not catastrophes. Like that straw bail house I read about somewhere in the mid west that had such a mold problem that it ended up being demolished. Or the other day, I was reading a back JLC article about some timber frame house that rotted off it's foundation in a short period of time. (not saying that there is anything wrong with either of these building techniques, just that something went drastically wrong).
To me, many of us have to change our way of thinking, and not necessarily accept "we've been doing it this way for 20 years" as a good answer. Still, I'm perfectly happy to just stay on the leading edge and let others put their projects out there on the bleeding edge. For example, 10 years ago, I think the Superior Walls thing was under the bleeding edge technology category, and someone else probably found out what happens if you use the wrong gravel, or whatever. Now it's moved to an accepted leading edge technology and I'm all for it if it's feasible for the particular project.Matt
Matt, you sound like someone I'd enjoy sharing a cold one with. Merry Christmas to you.Andy Engel, The Former Accidental Moderator
A cold one... mmmm... sounds good. I bet they are cold up there in new england too.... I'll meet you in the Tavern some time... Matt
Even the archy who haas inspired you would still be learning if he were still alive..
Excellence is its own reward!
>>The architect Frank Loyd Wright invented and used "rubble trench"
Invented? The railroads came well before he did - and I suspect they got the idea from somewhere.
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