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I am about to pour a 7’x4’x4″ concrete slab using bags of concrete mix. I have my form (wood – boards & plywood) 95% finished and want to pour this weekend if the rains stop. My slab is about 7′ above ground, and will be a continuation of a 4’x4′ porch slab. I built a cinder block wall on 1 long side, the house on the other long side, and the existing slab is the 3rd side. 4×4’s & plywood support the slab – no strength problems here. (A rebar grid will strengthen the slab.) I have several gaps at various points along the edges of my form that range from 1/8″ to 3/8″ (ok, 1/2″). Some are on the bottom, some are on the vertical edge. They are no longer than a few inches at any point and taper to a close fit. Some gaps occur where the form overlaps the existing wall and the 2 don’t match exactly (ops!).
What is the best way to handle these gaps? Some I can put a wood plug/strip in. Will caulk hold for the side gaps? A dry mix (i.e. 4 qts per 80# bag) should reduce flow also I think. Any suggestions are well appreciated. (PS I’ve omitted a lot of details here, so assume that everything is good except the gaps.)
Thanks! Alex
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Hi, Alex. I've seen spray foam used in similar circumstances to plug gaps. The foam was allowed to cure and then sliced to conform to the inner face(s) of the form.
*Thanks Don!
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I am about to pour a 7'x4'x4" concrete slab using bags of concrete mix. I have my form (wood - boards & plywood) 95% finished and want to pour this weekend if the rains stop. My slab is about 7' above ground, and will be a continuation of a 4'x4' porch slab. I built a cinder block wall on 1 long side, the house on the other long side, and the existing slab is the 3rd side. 4x4's & plywood support the slab - no strength problems here. (A rebar grid will strengthen the slab.) I have several gaps at various points along the edges of my form that range from 1/8" to 3/8" (ok, 1/2"). Some are on the bottom, some are on the vertical edge. They are no longer than a few inches at any point and taper to a close fit. Some gaps occur where the form overlaps the existing wall and the 2 don't match exactly (ops!).
What is the best way to handle these gaps? Some I can put a wood plug/strip in. Will caulk hold for the side gaps? A dry mix (i.e. 4 qts per 80# bag) should reduce flow also I think. Any suggestions are well appreciated. (PS I've omitted a lot of details here, so assume that everything is good except the gaps.)
Thanks! Alex