I have a situation where an old wood-framed garage with a concrete slab has been jacked up about 6" to increase the door heights and head room. Currently the studs are just resting on little brick stacks. What would be right approach for properly establishing footings for the raised frame?

  • Are there existing anchor bolts? Aside from that, can you raise it another brick to give more working room, then bring it back down? – Jack Feb 6 '18 at 20:03

If the existing slab had extended under the base plate of the wall studs then it is a common procedure to use a row of concrete blocks along the edge of the slab to create a curbing to provide the fill-in for the space where the walls were raised up. The best situation would of course would be to have raised the walls an inch or so above where the top of the block row will come so that it is possible to properly mortar in the concrete blocks and get them leveled and even.

If the concrete slab surface is clean the mortar under the concrete blocks should bond the blocks to the slab. If there are hold down bolts embedded in the slab some consideration needs to be made to extend those up to the above the row of blocks so that there is provision to re-anchor the base of the wall sections back down onto the top of the row of blocks.

For this application I have seen solid concrete blocks used for when the curbing height is 4 or 5 inches. Concrete blocks with holes are common when the curbing height is 8 inches. The holes would of course face up and down. It would be your choice to choose to fill the block holes with concrete mix or not. It is common that the holes that accomodate the hold down bolts are filled.

Note that when laying in the curbing blocks some accommodation needs to be made to plan the lengths of some blocks so that webbing in the blocks does not come right where hold down bolts would be located.

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  • So the studs are attached to the curb with hold down bolts attached to what, an angle plate of some kind? – Tyler Durden Feb 6 '18 at 18:51
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    Like I mentioned in my answer the normal method is to extend the existing hold down bolts that should have been in the slab. The extensions can be handled in various way.....weld new bolts by lap joint to existing bolts....bolt down an offset bracket to the existing bolts and new bolt part of the bracket....or use threaded couplers to join extension threaded rod directly inline with the existing bolts. Of course if there were no existing hold down bolts then you have to choose to have none above the curbing or to devise some other solution. – Michael Karas Feb 6 '18 at 19:05
  • @MichaelKaras In your case, lapping the anchor bolts is not acceptable. Welding or couples is the only answer. Lapping requires a minimum of 30 bar (or bolt) diameter to develop full strength (tensile strength). That would be about 15” for a 1/2” bolt. – Lee Sam Feb 7 '18 at 3:00
  • @LeeSam - Your response confuses me some. When I mentioned lap joint I specifically said it would be a welded joint and yet you are saying that a welded joint would be OK. I think you have to clarify more what you think a lap joint would be. – Michael Karas Feb 7 '18 at 3:13
  • @MichaelKaras Oh, I read it as either welded, lapped or coupled. Lap (splice) would not work for tension splice. – Lee Sam Feb 7 '18 at 5:51

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