I’m designing a few bedrooms to go on top of an existing, 60 year old masonry garage in Chicago. There was some serious settling/upheaval from two large trees, since removed. See pictures. A structural engineer was brought in, and to my surprise, he said “Patch it up as best as you can, but it should be fine.” Then we checked the foundation, and found that the garage has a 34″ deep foundation wall, but with no footing. The connecting breezeway room has a 27″ deep foundation wall, again with no footing, and we’re building over that, too. The garage has about 62 linear feet of foundation wall, and the breezeway has about 35 linear feet. I called several foundation repair outfits, and got one and a half estimates, and the news is grim. It could be a dealbreaker for the client, who is a Rabbi with a wealth of kids, but money… not so much. (Child #8 is on the way, and we’re adding 5 bedrooms, so my wife and I have been referring to the project as “The Rabbi Hutch”.)
The first guy Jesus (“Hay-zoos”) came by and proposed a ram-jack system for sinking foundations: bolt steel plates to the foundation wall, ram 4″ diameter schedule 40 steel pipes down as deep as 50 feet till they get 30 tons of resistance. Jesus gave me an off-the cuff estimate of 30 grand, and said a formal estimate would be in last Monday. I hadn’t heard from him by Wednesday, so I sent an email, and then heard back from the company that he “no longer works for this company”. I don’t know enough about religion to know whether a guy named Jesus would be reluctant to work with a Rabbi, or the other way around, but presumably he left for other reasons. We’d have to start over with another guy coming out to make an estimate, but I was fine with just dropping it, thinking the Rabbi would never go for $30 grand he wasn’t expecting to have to pay.
Then I heard back from another company that just works with concrete. They made a nice looking proposal, till you get to the bottom line: $74,550. I thought underpinning would be the cheaper option. We’re going to get a few more estimates, but I’m suddenly less optimistic.
The contractor is the rabbi’s brother (my former electrician) and is a creative, no-nonsense guy who wants to make sure his brother has a smooth, minimally expensive experience. So suddenly I’m thinking this: Buy a bunch of shovels, go pick up a van load of hardworking day laborers who assemble in a park in the city (which is somehow a city sanctioned arrangement) and have them start digging. Have plenty of lemonade on hand and after a little while, you’ve dug down enough and can call the concrete truck. I suppose we should do it in sections, since the building won’t float long enough for us to enjoy the convenience of doing one big pour. I know this is hard work, but it’s work, not rocket science, and $75 grand sounds like the guy doesn’t want the job. We’ll need to research the permit situation and what kind of concrete to use, steel, etc., but I wonder if you could get away with digging a footing-shaped trench under there, and keep the formwork to a minimum.
Another option would be to build a steel framework within the garage, on four posts, to support the new second floor and attic. Besides having two structures moving independently of each other, the problems there are: steel is expensive, you would need to support the rooms above the breezeway room (connecting back to the house) possibly with more steel, and you would need to have foundations for that, too.
I didn’t come up with this plan too fast. I came up with it half-fast. (Say it out loud.) What do you think? What am I forgetting? Thanks.
Replies
The settling/cracking in your pictures isn't pretty, but isn't too bad for a 60-year-old structure. You say there's "no footing" under the foundation, but the foundation goes down what is likely a reasonable distance for Chicago, and is presumably at least as thick as the walls (which are how thick??).
Have you asked the structural engineer if he's worked the calculations for the bearing ability of the foundation sans footing? It may well be that it is sufficient as it is, especially if the new structure is to be frame, with no additional masonry.
If the existing foundation is not sufficient, it may be more economical to install pilasters to support the new structure, vs trying to shore up the existing foundation.
I forgot to mention: Chicago code, and perhaps common sense, dictate having a footing 42" deep to get below the frostline. For the 34" deep garage foundation wall, that would mean just putting an 8" deep footing beneath the wall (somehow). For the less deep wall beneath the breezeway, we'd need that much more. But thanks for the idea. I'll avoid THIS particular structural engineer, though, as everything he does seems to be over-engineered, inefficient, clumsy, and uses a lot of expensive steel. I don't need Santiago Calatrava here, I just need the thing to stay put. But it could be that, for a wall like that, 4" of CMU and 4" of face brick, would, in real world terms, do just fine. How cold does it have to be, and for how long, to move around a brick garage with a 34" deep foundation wall? It could be that an engineer who isn't locally famous for killing houseflies with sledgehammers would say "go ahead". Has anybody ever seen an 8" foundation wall with no footing?
Done all the time. Think floating slabs with thickened edges.
I really think you need to talk to an engineer as Dan has suggested. I didn't open the picts as it takes too long, might want to resize to help pleople with dial up connection, or slow DSL!>G<
Thanks for the input. I'd be a lot quicker to call the structural engineer if it didn't seem like he charged $200 every time he picks up the phone. We're going to look into finding another guy. (Our complaints aren't just with his expense, more about his style.) Went and did a little digging this morning and found lots of hard clay in the dirt, and the sides of the foundation wall are not smooth. With the soil being this firm, it looks like they just dug a trench and filled it. Sorry about the big pics- forgot about my days gone by when it took more time to open big files. Once I went to wireless, there was no looking back...
We only need to go 42" here, and it gets a lot colder than in Chicago.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
After looking at the pics I was going to say the same thing. In older brick structures this is pretty common.
I'm currently in a brick house and there are cracks at the usual places but usually someone along the way has filled them with something. So it doesn't look so bad.
In the case of my house they filled the cracks with silicone caulking. It blends in pretty well!
My point is this is common but the cracks get filled. Yours looks worse.
"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
Edited 8/12/2009 11:11 pm by popawheelie
Your walls without footings are probably grade beams, as good or better than a separate footing and wall. Because the building withstood the test of time,at least til the trees were removed,then the grade beams did their job. I understand they are not deep enough to come up to code. After consulting with an engineer or architect and if the building department signs off,then do as the first engineer suggested. Patch up the mortar joints and any loose brick first. Now the architect,or engineer can determine if a new structure can be supported on the existing foundation.
I would guess that you do not need extensive foundation work. Your grade beams,34" high and the other 27" high may be a lot more substantial than a standard 8x16" footing and an 8"block wall.Hopefully I guessed right , and you can get to the addition work soon.
mike
mike 4244 and Sam T (and everyone) Thanks for the suggestions and input on the foundations with the missing footings. Had a concrete guy come by today and he made some good suggestions: dig adjacent to the trench (and undercut it a little), drill and epoxy rebar into the existing foundation, and make sure the new foundation would go deep enough. I wouldn't guess that rebar has that much shear strength, but I suppose if you use enough of it... The breezeway room is 15 feet wide (where it connects to the garage) and 19 feet long. He suggested we could just leave the breezeway room alone, let it sit there as it has for 60 years, and span over it with open web trusses or something to do the second floor rooms, basically suspend them between the stabilized garage and the existing masonry home. I wish I could hear from an engineer who would sign off, even off the record, on the concept of doing nothing. We are building a frame structure on top of a masonry structure that is 8" thick and about 11 feet tall, 14 feet tall if you count the foundation: it's not like we're doubling the weight the foundation will have to carry. I wonder if we're adding 10% or what. Maybe the point is moot if we're actually above the frostline, but does the frost really go down 42 inches around here these days? Either a big bag of money needs to fall out of the sky or some other way to know the right thing to do will come to me in my sleep over the weekend, but this client doesn't have a lot of money to burn, and what money there is needs to be spent intelligently. Another option would be to demolish the garage (but not the breezeway room) build a new frame structure there, and bridge over the existing breezeway to the house....
A pilaster is just a pier that gets attached to a wall. Dig down to the frost line just enough for a square pier footing and pour that. Next, add rebar "dowels" into the existing wall, in line with the pilaster location. The pilaster footer should have at least two upright rebars sticking up from the footer. Tie these to the dowels and form up a pilaster alongside the inside of the wall. Pour the pilaster. You can even place anchor bolts in this pilaster during the pour. Use these to support the load with a beam between two pilasters. All new framing the can be supported on just the pilasters. And you can leave the "old" wall in place. Note: the pilaster footer will go from the frost line up to the bottom of the existing wall. That way it supports both the new pilaster AND the existing "old"wall (grade beam).
Edited 8/14/2009 3:01 am ET by whitedogstr8leg
I wish I could hear from an engineer who would sign off, even off the record, on the concept of doing nothing. We are building a frame structure on top of a masonry structure that is 8" thick and about 11 feet tall, 14 feet tall if you count the foundation: it's not like we're doubling the weight the foundation will have to carry. I wonder if we're adding 10% or what. Maybe the point is moot if we're actually above the frostline, but does the frost really go down 42 inches around here these days?
Actually you may be doubling the load on the foundations. the existing slab on grade likley does not place much load on the existing foundation. The new floor will add 10 PSF DL and 40 PSF LL. The exisitng structure is showing evidence of movement. the movement may be from frost heave.
Yes the frost can get to 42" or lower. Watch the news last winter when the giant pot hole from a frozen water main that was 6' down broke? It is common for architects to use 48" to bottom of the footing.
One last thing the soil bearing pressure around Chicago can be very low and all foundation walls should have a footing. No design professional in there right mind would propose a foundation with out one.
Repairing the foundation may seem costly, but what is the cost if the new structure has problems related to the foundations and has to be repaired?
> the existing slab on grade likley does not place much load on the existing foundation.I have to believe that the existing solid masonry walls put significant load on the foundation. If the new structure is frame it would not add that much more, relatively speaking.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
I ran some quick numbers and you are correct.
The block and brick weigh about 90 pounds a SF. For a 9 foot tall wall that would be ~800 a linear foot. If the new floor joist span 24' and the design load is 50 PSFthey will add 600 pounds a linear foot to the wall. This is the " design load" which will probably never be reached.
It could be significant increase to the loads on the foundation even 300 PLF would be 37% increase to the foundations and the existing walls are already showing signs of movement.
>>There was some serious *** upheaval from two large trees, since removed.
mikeymo,
Now that they're gone, you will have some settling as the roots rot away.
We killed a cottonwood 3 years ago and are just starting to see the slab floor settling back down.
I like the "Lots o' shovels" plan.
Excavate 6' of wall bottom, pound 2' of #6 8'long into one end (unexcavated,) pour 4 linear feet of footing. Clear another 4' of wall, opposite the end with the rebar stuck in the dirt, tie in 2 6' pieces of #6 to the 2 pieces sticking out of the fresh footing and pour 4 more feet of footing. Repeat as needed. When you get around to where you started, you'll have 2 pieces of rebar (sticking out of the first pour) to tie to.
After all that, I would cap the wall with something to tie all the pieces of wall together.
Instead of spending $75K just to repair what's there so you can do an addition, demo the whole thing and frame a nice complete new structure. Bet that'ld be less than $75K.
SamT