sderose
10-25-2003, 12:21 AM
I want to build a storm/whatever shelter. The existing basement room is 15*15, with 2 adjacent exterior walls of 8" concrete (house above is 2 wood-frame stories, for whatever that says about the footings).
I'd like to pour 6-8" thick reinforced concrete for the other two walls, both of which are already load-bearing (one on a 12" high I-beam at the house centerline; the other on doubled 12" constructed wood trusses).
I'd then like to fill the joist spaces to make a 12" thick reinforced concrete ceiling (was thinking of replacing the constructed wood joists with metal floor trusses, which would become part of the reinforcement for the concrete poured around them).
My question is, what do I need to do to support all the extra weight (about 17 tons of ceiling slab and 11 tons of new walls)? I imagine I have to cut the floor slab (presumably 4" thick) and pour footings for the new walls. But will the existing walls take the extra load? Half of 17 tons, sitting on 30 running feet of walls, = 550 pounds per running foot. If the footings are 16" wide that's about 425psf being added.
If that's likely too much, what can I do to hold up the ceiling on those two sides? Steel beam on 3 posts? Concrete pilasters? Undercut and widen the inside side of the footers? Pour a 2nd footing outside the exterior walls, and a second (tied-in) wall doubling the thickness from frost line up to where the joists sit (about half the total wall height)? That would add a lot of strength against shearing at grade, projectiles, and radiation. Or is this all infeasible and I should give up?
Many thanks for any help!
I'd like to pour 6-8" thick reinforced concrete for the other two walls, both of which are already load-bearing (one on a 12" high I-beam at the house centerline; the other on doubled 12" constructed wood trusses).
I'd then like to fill the joist spaces to make a 12" thick reinforced concrete ceiling (was thinking of replacing the constructed wood joists with metal floor trusses, which would become part of the reinforcement for the concrete poured around them).
My question is, what do I need to do to support all the extra weight (about 17 tons of ceiling slab and 11 tons of new walls)? I imagine I have to cut the floor slab (presumably 4" thick) and pour footings for the new walls. But will the existing walls take the extra load? Half of 17 tons, sitting on 30 running feet of walls, = 550 pounds per running foot. If the footings are 16" wide that's about 425psf being added.
If that's likely too much, what can I do to hold up the ceiling on those two sides? Steel beam on 3 posts? Concrete pilasters? Undercut and widen the inside side of the footers? Pour a 2nd footing outside the exterior walls, and a second (tied-in) wall doubling the thickness from frost line up to where the joists sit (about half the total wall height)? That would add a lot of strength against shearing at grade, projectiles, and radiation. Or is this all infeasible and I should give up?
Many thanks for any help!