Anchoring floor joist to cinder block wall?

Question

I'm re-doing the second floor in an addition. Addition was made with cinder-block walls. Joists were toed into cinder-block. After sub-floor was removed they wobble (left to right) and they are also not level. I want to raise some of these and tie them to the exterior wall using joist hangers. I need to raise some of them and anchor all to cinder-block wall. I plan on gluing and anchoring a 2x4 along the level line, pulling the joists to the bottom of the 2x4 and attaching hangers using glue and anchors. The anchors I plan on using are tapcon. The cinder-blocks are hollow. Am I on the right track? Can I run bolts through the 2x4 and down into the joist in order to pull them up (no access from below without gutting downstairs room too) or would that reduce the shear strength of the joists?

Answer 1

Sounds like you are on the right track. The only problem I have is that there is no moisture barried between the cinder block wall and your lumber. Cinder blocks are porus and suck up water. When ever a house is built and lumber is laid on a concrete foundation a vapor barrier is always used. That's why cellars are damp.

Another idea would be to bolt a piece of 2x6 or 2x8 pressure treated lumber to the wall and mount you floor joists to that. Then you could level the pressure treated lumber and use joist hangers for your floor.

It's hard to give exact advise without seeing the job. Hope I helped.

Answer 2

I think I have the idea of what you are trying to achieve. First of all there are a couple of things you may want to try that will be helpful. Without seeing the job, I can only make suggestions based on similar situations that I have been in in the past when doing remodeling work for my clients.

So, you have taken up the sub floor and now the joist are exposed. You want to attach the joist to a cinder-block wall and level up the joist that are lower then what they should be. Hopefully I understand the matter correctly.

My first suggestion is this. Let's suppose the floor joists are made of 2 x 8 material and the joist space is 16" on center. This would mean that there is about 14 1/2" between the joist. Determine the height of where you want the joist to be and then take a 2 x 4 that will span across the width of the room over the joist. Place a level on top of the 2 x 4 and after it is level, draw a line under the it at each end.

Next take a chalk line and hold it against the mark at one and have someone stretch it across the mark at the other end and then strike the line. This will act as the level line you want the top of your joist to come to.

Now, starting at one end cut 2 x 8 treated block 14 1/2" long or whatever the actual width between the joists is, and then you are going to attach it to the block wall, holding it up against the chalk line, with glue and tapcons. Once the block is in place, you can take the joist and nail and glue it against the end of the block.

Proceed to the next block and hold it tight against the joist you just installed and follow the same procedure. Keep adding the blocks making sure to keep them even with the level line and taking a new measurement between the joists each time to keep the correct spacing. With this method, you will not need joist hangers.

If you prefer, you can s***w or bolt the joists into the block, but be sure to pre-drill holes as to avoid splitting the blocks. When you are done, you will have a very tight fit, strong floor frame. Just install the new sub floor and you are good to go.

The second method is similar to the first except for this. If you can cut 1 1/2" off the ends of the joist so that they are 1 1/2" short of the block wall, you can then take a 2 x 8 piece of treated lumber, or whatever the size of the existing joist are and insert it against the wall. Hold it up to the level line and fasten it to the wall using glue and tapcons.

After that you can proceed with the block method already described above, only this time you will nail the blocks into the 2 x 8 board you just installed, or you can use joist hangers which can be nailed against the board and install the joists that way. This is a good choice especially if it is required by the building code in your area.

Sorry this is so long. I hope this helps, Rick