concrete pad thickness and what under it?

[greenthumb]

I am building a tool shed. How thick of a concrete pad do I need. It will only be used for garden tools and foot traffic, maybe a potting area for the garden. the structure is made of wood. Last question should I use sand or gravel under the pad before I pour

 

[cowboydoc]

4" should be fine. You can use either sand or gravel. Sand will probably be easier to get level.

 

[Gary_in_Indiana]

I tend to overbuild everything and I'd be content with a 4" slab for a garden/tool shed. Since you're not going to put any real weight on it I don't think the base you use will matter that much. I'd probably use whatever I had around or whatever was easier for me. Either will do the job for you.

 

[gsxr1100]

ummm, well my walk ways are 6 feet wide, 6 inches deep and 60 feet long. Total of 7 yards. Concrete is cheap..

 

[CTyler]

Hi, how big is your tool shed?

Sounds like 4" would be enough. If you use sand you should pack it, pea gravel it doesn't need it.

 

[greenthumb]

shed is 15 1/2 x 11 1/2. I have been leaning towards pea gravel also since I have a pile of it taking up space behind the barn. two final questions. where the shed is going slopes very slightly. my question is do I dig out the high end or back fill the low end to get things level for the forms? second questions is best way to attach the shed to the concrete, use bolts sank in the pad, concrete screws or ram set nails? thanks for all your help. I will have everyone over to help paint when I'm done.

 

[Soundguy]

If you know exactly where your mounting points are.. you could use j-bolts, or even threaded rods for tie plates.. etc.

3" of concrete is probably fine for the weight.. but i would worry about cracking.. plus.. going 4" gives you flexibility later... throw some wire fabric material in there too.

You could drill and use anchor bolts .. but like I said.. if you measure correctly.. you could set the bolts, etc.

Soundguy

 

[yellowyj]

I would dig out the high end unless it is just a small difference in elevation. It is hard to get good compaction if you have to back fill a lot.

If you do back fill the low end, compact the fill in 6 inch, or less, layers.

I prefer bolts sank into the pad to secure the building to the concrete.

 

[Currmudgeon]

I don't like to do less than a four inch slab. The thin spots (and there will be some) on a thinner slab will really kill you.

Some wire mesh will help reduce shrinkage cracking, but won't really strengthen the slab much. For that application fence wire is probably OK. Hook it up off the bottom as you pour, so it's actually embedded in the concrete. Try to get the wire in the center of the slab, as you want about two inches of cover on the steel.

Concrete shrinks when it sets. It cracks when it shrinks. The grooves you see in sidewalks and concrete parking aprons, are contraction joints to force the cracks to occur where you want them, and to hide the cracks. (If you can't prevent something, call it deliberate. /forums/images/graemlins/wink.gif ) The joints should be spaced d/24 maximum, or two feet per inch of slab thickness. Make the joints even and the panels as close to square as you can.

 

[CTyler]

</font><font color="blue" class="small">( my question is do I dig out the high end or back fill the low end to get things level for the forms? second questions is best way to attach the shed to the concrete, use bolts sank in the pad, concrete screws or ram set nails? )</font>

If you dig out the high side make sure you still have drainage away from the shed.

I would use the J bolts, just make sure you don't have a bolt coming up where a stud will be. Measure things out and mark your forms so you know where to put them.

There is nothing wrong with nailing to the concrete though and its slightly easier if you have the nailer to do it.