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lbird20033 09-23-2008 05:47 PM

pour own footers
 
i want to know if anyone can tell me how many bags of concrete i need to mix to pour a footer for a new house. it is 24x30 and the footers will be 2 feet by 8 inches. also does it have to be a continous pour or can we do it a little at a time and add rebar to join?
thanx
lisa

concretemasonry 09-23-2008 06:22 PM

The cheapest way from a concrete standpoint is to order a truck and pour it all at once. - No question, no matter where you live unless you buy gas for nothing.

If you go to all the expense and trouble, you can pour in sections and run rebar across the formed cold joints. In some areas you need rebar continuous and in some you do not need any rebar, but it is cheap insurance. Your footings may be a little wide, but apparently you have sized them for the wall and loads you have.

joed 09-23-2008 06:55 PM

You are looking at about 5.3 yards of concrete. At 6 bags to the yars you need about 33 bags of cement to go into your 5.3 yards of sand gravel mix.
If you are going to use the redimixed bags of concrete like Qiuckcrete then you need about 240 bags of 80 pounds.

8" doesn't sound very thick for a footer.

lbird20033 09-23-2008 08:40 PM

pour own footers
 
do you think 8 inches is to shallow? we asked around and thats what we were told was the right depth?

concretemasonry 09-23-2008 08:52 PM

For a normal basement, 8" is enough and will meet almost any code.

The only thing to change it is if you have very poor soil and need a wide footing. If you have a wide footing some codes may require a thicker footing, but that is rare. A wood basement is built without a concrete footing since a house does not weigh much.

Do you need extra weight to prevent the house from blowing away in a tornado?

Check you local code requirements and they will probably say 8" thick.

Termite 09-23-2008 09:07 PM

Quote:

Originally Posted by lbird20033 (Post 160672)
do you think 8 inches is to shallow? we asked around and thats what we were told was the right depth?

8x16" is a common size for footings. Typically anything wider than 16" is going to have to be thicker. Your footing's size should be engineered to work with the soil's bearing capacity on your lot.

You should not even consider doing this with sack concrete. You want to get the concrete placed quickly, and you're not going to do that with sack mix, even if you have a powered mixer. Pouring concrete in multiple pours causes what's called a "cold joint", which is a failure of the new concrete to correctly bond to the hardened concrete you're pouring against. It creates a weak point, and that's something you don't want in a footing.

You need to call a concrete company. It will be cheaper anyway. Guessing...Say $120/yard...That's $720. How much will 240 bags of (inferior) sackrete cost you, plus rental of a mixer?

Yes, you need rebar. There are occurrences when it isn't needed, but that is very uncommon. It is always a good idea. If it were mine and it were 24" wide, it would be no less than 12" thick and it would have three #4 bars in it. Once again, that depends on soil conditions, but pure physics dictates that footings that are thin and wide aren't going to do as well as thicker footings when bearing loads from above.

You need to contact a structural engineer, or at least the local building department.

James Con 09-23-2008 11:23 PM

Doesn't the footings have to be a monolithic pour by code. And also does'nt footing mix have larger and more aggregate in the mix, Something you won't get from a bag mix. Another thing you should look into is the eufer ground incorporated into the rebar that is in the footing, If rebar is used in the footing it must also be used as a eufer ground. At least in my area it's required.

Termite 09-24-2008 12:17 AM

Any inspector worth his salt is going to instantly disapprove a cold joint and require an engineer's review. I've had entire foundations torn out because they couldn't get an engineer to sign off cold joints in the walls.

Ufer grounds are not new, but they are a new code requirement in residential construction. Yes, it bears mentioning and is definately something that the OP should determine if they're required to do. You can't get a better ground, that's for sure.

handy man88 09-24-2008 08:30 AM

Quote:

Originally Posted by lbird20033 (Post 160635)
i want to know if anyone can tell me how many bags of concrete i need to mix to pour a footer for a new house. it is 24x30 and the footers will be 2 feet by 8 inches. also does it have to be a continous pour or can we do it a little at a time and add rebar to join?
thanx
lisa

I don't want to rain on your parade, but if you're just starting out on building a house, and need to come onto this blog to ask questions about pouring the footers, then you may seriously be in over your head.

Pay the money and have a pro do this for you. You won't regret it.

Footers are critical to the structural integrity of your house.

They probably need to be poured all at once, not piece meal over time depending on how quick you can mix and pour from your wheelbarrow or mixer while trying to ensure consistency.

Have you even thought about digging the trenches and making sure everything is level yet?

The money you save in the long run will either be used for repairs or therapy, or both.

I recommend you don't do it.

lbird20033 09-24-2008 08:58 PM

we have someone coming to dig the trenches these questions are just for my own peace of mind. so i have a little better understanding of why things are to be done a certian way

Termite 09-24-2008 09:10 PM

Trenches? Trench footings are normally much, much deeper than 8".

If this is a conventional spread footing with a foundation wall on top of it, you should not be digging trenches for the footings. You should be forming them up out of lumber above the bottom of the excavation. Otherwise you'll have a heck of a time getting the basement slab poured correctly...You'll end up trying to excavate the inside a few more inches in order to gravel under the slab.

Termite 09-24-2008 09:23 PM

Aaaaand...

You'll end up buying more concrete for your foundation walls to reach the same height as they otherwise would.

James Con 09-24-2008 11:55 PM

Quote:

Originally Posted by lbird20033 (Post 160968)
we have someone coming to dig the trenches these questions are just for my own peace of mind. so i have a little better understanding of why things are to be done a certian way

If it's possible talk to the mason you are gonna use to do the block work and get him and the excavator together and go over the job at the job site. Because if the excavator doesn't leave enough room when digging the frost line for the mason to get in there to lay the footings and lay the block up, the mason might charge you more due to the pain in the butt it is gonna be for him to get in there and bring up the block to grade and also it will be a b!tch to parge. Most excavators know there jobs, but then again it won't hurt to get them all on the same page. Just a little food for thought.

Maintenance 6 09-25-2008 07:41 AM

Quote:

Originally Posted by thekctermite (Post 160974)
Trenches? Trench footings are normally much, much deeper than 8".

If this is a conventional spread footing with a foundation wall on top of it, you should not be digging trenches for the footings. You should be forming them up out of lumber above the bottom of the excavation. Otherwise you'll have a heck of a time getting the basement slab poured correctly...You'll end up trying to excavate the inside a few more inches in order to gravel under the slab.

It's pretty common around here to dig a basement 8" lower than than the finished slab elevation, then dig an 8"x16" trench around it for a footer. After the block is layed, 4" of clean 2B stone and a 4" basement slab. It's not exactly common to form up footers. It could be soil condition driven.

Termite 09-25-2008 08:39 AM

Quote:

Originally Posted by Maintenance 6 (Post 161074)
It's pretty common around here to dig a basement 8" lower than than the finished slab elevation, then dig an 8"x16" trench around it for a footer. After the block is layed, 4" of clean 2B stone and a 4" basement slab. It's not exactly common to form up footers. It could be soil condition driven.

Ahhh, a regional thing. We all definately have different methods across the country. Here, you'd pretty much never see a block foundation on a new home.


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