Loft for garage

I have a 15' by 30' foot cinder block garage with high ceilings. I would like to build a storage loft in half of the garage. I am debating on supporting it from the floor with 4x4 or 6x6 along the walls or only attaching it to the walls in some way. three edges are cinder bocks. Or maybe some sort of combination.
Currently it supported from the ceiling I think if I store to much stuff up there is could be very bad.

Also for the decking should I just use plywood or something else?

Tanks for your thoughts and ideas!
--Bill

 

well i wouldn't recommend using posts to bear any significant amount of weight without a footing, granted i doubt your slab will buckle with only a loft resting on it. you'll have to ask your local officials if that sort of thing is acceptable (plenty of people build shelves and such in this manner but your talking 15'x15' which is quite a bit larger).

i would instead suggest, provided that you have access to the cells of the concrete block from above, pour concrete down into the cavities of a couple blocks to create a solid wall (do this where you want the edge of the loft to protrude to i.e. 15' from the side wall). At this location you can attach a beam hanger with 3/4" expansion bolts. do this on the opposite wall and suspend a beam from the hangers so that you have a beam running from front wall to back wall. Then attach another beam in the same manner closely along the side wall and hang 2x joists in between the beams. Cover with 5/8" plywood or 3/4" OSB (both are virtually equivalent in strength, but plywood resists expansion and warping better, OSB is cheaper). Let me know if I'm correct about the loft area being 15'x15' and I can give you the beam and joist sizes you'll need.

 

Thank you for your response, looking back I was not real clear on everything. The interior width of the garage is 11' 10" and the going to the back wall is about 29'. The building is 22 cinder blocks tall in the middle (the roof is one slope going up in the far back) So in the back half of the garage I want to build a loft (11'10" wide x 12' deep 8' to 9' above the ground) . I do not have access to the top of the blocks(it is all capped). Also the floor is not a slab it is just a wide concrete footing around the perimeter with crushed stone in the middle. Hopefully this is a better description of what I have and am looking to do. could you please help me out again and give me an idea of how to support the loft? (wall or footing)

Thanks again

 

Why not use a beam spanning the 11' 9" width? Support the beam with a post on each end. Rest the posts on the exposed footer and attach them to the wall. Hang perpendicular 2X8 joists from the beam, attach a ledger to hang the joists on the other end and nail the flooring to the joists. I would probably use 3/4" OSB for flooring only because it's cheaper than plywood.

 

well i have a hard time suggesting an alternative fastening method with much confidence. if there is a way to remove the "cap", of which i do not know the nature of, then by all means go with the method i described earlier for the sake of longevity. its the best way.

but if you cannot, perhaps you could anchor the 3 masonry-supported sides of the loft with butterfly type anchors (the biggest diameter you can find). the type that you hold closed and shove them through the hole and they open up. Now, since the typical face or shell thickness of CMU block is 1.25", these anchors should be sufficient if you use them liberally, but theres no way i can be sure; its not my loft, and i dont know whats going to sit on top of it.

you would bolt a 2x10x8" long to each side wall and using joist hangers, hang a double 2x10 beam between them (this would be the 11'10" dimension). then bolt a 2x6 to the back wall and hang 2x6 joists on 12" centers between it and the 2x10 beam. when bolting to the block, use a zig zag pattern (top and bottom) and put a bolt in each hollow core of each block.