How much concrete will I need for this shed?

Question

The shed is going to be 120 " x 140 " and I guess like 4 " thick. Home Depot has 80lbs bags for like 5$ a pop so how many do you guys think i would need? Also, When laying the foundation should the concrete be like 2 " under the ground and 2 " above ground or is 4 " too think all together. I have built sheds in the past but never layed a concrete foundation. Just want to build my dad a really nice one while he is gone on a work trip.

Answer 1

I wondering why you want a a solid slab for a shed. Is this going to be stick-built by hand or purchased, delivered and set in place? I've done sheds that merely rest on concrete piers with floor framing. You save on money, materials, labor and time by propping up the structure on pads and piers. Plus,the structure is higher off the ground to avoid rot from the elements and bug infestations.

Go to the Sakrete website and use their online materials calculator at: http://www.sakrete.com If you're going the solid slab route, you should consider forming and pouring short stub walls to raise the structure above grade. This could also be done with CMU's laid on top of the cured slab with mortar. Remember to prep the slab area with plenty of tamped gravel or stone dust and let any excavated dirt settle before pouring concrete. Use reinforcing wire mesh in your slab or rebar and be sure to damp cure the pour for a week or so with a burlap cover and an occassional sprinkler to keep the concrete damp.

Hauling and mixing bags to a pour is a hassle. You should check out your local redi-mix company for a price quote and a delivery. Trust me...it's great when a truck loaded with redi-mix drives up to your pour and you'e done with the whole mesh in about 10 minutes. It's worth the extra money!

Good luck

Answer 2

Dude . I use this site for most calculations .http://www.concretenetwork.com/concrete/... . don`t forget to have at least 4" of gravel under it for drainage. Never put the pad under the grade for water problems . I would put it at least 3" above grade. My 12'x 16 ' shed is at grade at the back and 6" above in the front with 6" of 3/4 gravel underneath and I used a steel mesh at 1" and 3" to prevent cracking . But I also have to deal with temp swings from -20c in the winter to over +30 in the summer. 8 years old  and no cracks yet

Answer 3

you will need  two qubic years four inchs under ground .hubby does it for a living.

Answer 4

Volume is 120"x140"x4" cubic inches, divided by 1728 cubic inches per cubic foot = 38.89 cubic feet divided by 27 cubic feet per cubic yard = 1.44 cubic yards (say 1.5).

The bags will probably tell you how much mixed concrete to expect from each one. Considering the size of the bags, it'll probably be in cubic feet, so divide 39 cubic feet by the volume in cubic feet per bag to get the number of bags. Round it up to the nearest whole bag, and get a couple more for insurance. You don't want to run short.

However, this is a big pour. I don't think you can realistically expect to mix the concrete in a wheelbarrow fast enough to get it screeded and finished before the first loads start setting up. I'd say you'll need a portable mixer of at least 1/2 CY (and that sounds huge for a portable to me), plus some help. You'll need at least 2 people to do the screeding, and at least 1 of you needs to know how to finish concrete.

Do you have a truck? You might do better buying concrete directly from a plant, and renting a towable "buggy" like this: http://www.bartelsequipment.com/images/2... . They hold about 2 yards and have a dump function (which you can see in the picture). You'll be able to pour much faster, without having to stop and mix every individual bag, so you can concentrate on screeding and finishing instead.

And 4" thick is fine for a shed (my 10'x20' shed is on a 4" slab). Having all 4" above grade is fine, too. Just make sure the site is level and compacted.