specs for residential slab
I’m moving a small frame house (28×21′, floor and a half) onto a new foundation, then adding on to the house a bit. For the foundation I’m going to dry-stack concrete block and I’ve got bids from three local concrete contractors for an “alaskan slab” (why “alaskan”?). I’ve got my bids back but I didn’t give the contractors specs for the job (figuring they know more than I do), but now I have to call them back to find out what there specs are, because otherwise I can’t really compare their bids. What should I expect? The high bidder calculated his price based on a 6 inch slab, #5 rebar in a 3 foot grid, two rows of rebar in the footers, and – well I can’t find where I wrote how deep the footers and pads under lally columns would be.
I realize that there is no one-size-fits-all answer, but any offers as to what the specs should be? I am in central New Hampshire, the subsoil is hard clay, the water table might be close to the basement floor in a wet spring – but we are putting in a good perimeter drain system. I am not insulating the slab. The entire footprint will be about 880 square feet.
go with the high bidder, he know what he talking about.
What is an Alaskan Slab?
Too little info to make a good call on what you have asked!
Probably too many variables to fit into a written paragraph!
Maybe attach pics of your prints.
Is this going to be a basement, stem wall slab house, monolithic slab house, crawl space, or what? You seem to maybe be talking about a slab foundation but then mention things like dry stack blocks and lally columns.
What is the required footing depth for your area? If you don't know, tell us what part of what state you live in. Someone here will either know or at least have a pretty good idea. How sloped is the site? Also, tell us about the soil type and condition where the proposed building site is. Is it sandy fill? Mucky silt? Rock hard and parched red clay? 6" of top soil that needs to be stripped off to reveal soft, powdery when dry, light gray clay (which needs to be excavated too)? If you don't know get out a shouvel. Basically you are trying to first determine the soil is more mineral or organic which means what is the color and content of organic debris. Once you have determined how deep you have to dig to find non-organic type soil, you need to determine how granular the soil is. Clay has very small particles, sandy soil has larger particles, drains better, and can be more stable.
Your local contractors will be your best information resource for the above questions if you dont know and can't get the answers on your own.
Unfortinately, I think you have wasted these bidding contractors time. Some specs need to be included in the bids. After the fact verbal specifications aren't worth much. Even before-the-bid verbal agreements would be of some value, because then the contractors might be biding on the same thing.
It's a full basement, frost line around here, central New Hampshire, is apparently 6 to 8 feet down, depending on your elevation etc. There is close to 12 inches of topsoil on the site and under that is clay, mostly gray, sometimes yellow. I've been down in it to four feet, and it is hard digging by hand.I'm dry stacking block because that is something I can do myself and it seemed to me that it would be easier to have all the concrete work done at one time: the footers, and the basement floor, rather than having the floor poured later. All three contractors have been on the site, and know what I am doing.
I'm afraid to ask... are there permitted plans for this job showing what is required? If not, then you might be back here several times during the job asking us if the work is being done correctly. There's no substitute for some half-decent plans. For what you're doing a couple of simple section drawings would probably suffice.
No building code where I live - no permits. But you're right, I should have drawn a simple section and had it with me when I talked to the contractors, my mistake. I promise I won't come back to ask if the work is being done correctly. I asked all three contractors for two bids; one for a standard poured concrete full basement, and another bid for just a floor and footers for me to build a dry stacked block wall. This discussion thread started when I saw that the guy who was high bidder for just pouring footers and a floor was the low bidder if I went with a standard poured concrete basement, while the low bidder for just footers and a floor was the high bidder for the standard basement. I was puzzled. If everybody is calculating to the same specs then I don't have a problem, but I realized that if I discovered that they were calculating to different specs I would have two choices: either be stingy and take one of the low bidders, and hope I wouldn't suffer for it, or take the high bidder figuring he was giving me a better job for the money. I am NOT asking this forum which choice I should make, that is my responsibility. I was just wondering if there was a better way for me to think about this. Maybe there isn't.All three contractors have been working around here for a while and have solid reputations. I have no reason to think any of them would do a bad job.Anyway, thanks to all of you for your comments.
I'm not even close to understanding full basements but it seems to me that there is little difference between a retaining wall and the wall of a full basement. Any retaining wall over 4 ft in height requires engineering (measured from bottom of footing). How can you even think of dry stacking block to make a wall for a full basement without approved plans or engineered drawings? I know they use to just pile up rocks to form basement walls that still stand to this day but I don't think I'd trust their integrity. New construction and lack of drawings and specs seems like asking for huge problems latter on. JMTC