Posted by MoparNorm on Wednesday, March 10, 2004 at 5:32PM :
In Reply to: OT - Garage construction question posted by John on Wednesday, March 10, 2004 at 1:45PM :
John you have received some interesting and some incorrect answers, I won't dwell on that. I have been in the concrete business since 1968, here is what you need to do;
Building size; as big as you can afford, in any multiple of 4', that is the most economical division for building materials.
Footings; As deep as the frost line, if you have one, no less than 18" wide and 24" deep. With two #5 bars top and bottom.
Slab, 2,500lb psi mix minimum, 5" or greater in thickness. 4" is for sidewalks, the cost is minimal to do it right.
Compact the sub base until you are blue in the face and then soak it for 24 hours. Use 4" of sand or class 1 base if it fits your budget, under the concrete.
NEVER use wire mesh or waste you time and money with fiber reinforced concrete, it is a gimic and wire mesh causes more cracks and problems than it solves. Use grade 60 #4 bars, #5 if you can afford it, on 18" centers each way. (we are talking pennies here) use dobbie blocks to support the steel in the center of the slab, ideally 2.5 inches from the bottom. Use tie wire and tie every other re-bar intersection.
Did I say compact the sub grade?
Saw cut or tool, control joints at 15' maximum intervals each way, concrete continues to dry and shrink for about 30 years, it WILL crack, give it a place to do so that looks good and will not ruin the slab over the years.
Lastly, e-mail me, (or anyone else contemplating this work) if you require additional information.
MN
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