Advice on how to secure new joists to cement sill

[lupinfarm]

Pulled up section of floor in kitchen and found that existing
Joists rest on top of and are nailed into a cement sill/foundation.
Most of the existing joists are made up of bits of lumber cobbled
Together. The floor is very bouncy so I think I will have to install new
Bigger joists. Does anyone know what would be the best way to do this?

[SkipW]

Do you have room for a sill plate on top of the concrete?

Is there any kind of rim joist or just exterior sheathing. If not, what is the sheathing attached to?

Any way to box them at the ends, i.e.: create a rim joist first, and nail to it?

I suppose you could use blocking in betweeen joists and let them rest on the concrete.

What kind of access do you have / will you have? That may determine your actions.

[lupinfarm]

hi SkipW....I have uploaded a picture, had to wait as my internet was down. The brick wall you see in the picture used
to be an outside wall but the kitchen was built onto the what was originally the front of the house so now the brick wall is
an interior wall. the joists seem to consist of a 2x8 ( true 2x8) laid wide side down on top of the concrete sill and a 2x6 laid
on top of the 2x8. There is not much room underneath,probably not enough to accommodate a 2x8 or 2x10 attached to a wooden rim joist on the vertical plain of the sill. I don't believe there is enough room to put a wooden sill on top of the concrete sill as that would raise the joists up to high and they would be above the height of the sill at the other end. My thought was to use triple 2by8s or 2by10s and cut a notch in the end to fit over the sill the same height as is there now ( approx 3.5inches). The balance of the joist would sit in front of the sill and could be secured by toe nailing and blocking could be used in between the joists to provide more strength. I would draw a picture but I am no good at drawing.

[GothicHome]

Lupinfarm, I to have to deal with some rotted joists in our back addition. Fortunately I have lots of head room under the floor because it was once the coal cellar originally. My big issue is getting rid of a 2 inch drop from front to back while staying in the joist pockets.

[SkipW]

I just want to understand how it is now before going farther. Does the 'joist' consist of a 2x8 laid flat and a 2x6 on top of it like in the attached image? If so your space to replace is 3" between the sill and subfloor, thus we'd have to get creative with new floor framing to make it sturdy. are you planning on gutting the entire kitchen floor to the walls or are you thinking of a patch in place kind of project?

Edit to add: I can't really see in your pic what's there. But in re-reading your post, you talk of notching married two-bys to make them fit the 3.5" space. While this is not the best way to support a floor (really weakens the strength of the wood, also creates a place to crack and split), you might be able to gusset the notches to give them back the strength they need to make it work.

[lupinfarm]

Hi SkipW yep your diagram is pretty accurate. We are planning on
Removing all the joists as they seem pretty rotted out at the ends. What do you mean by" Gusset" the
Notches?. Could you suggest another way that would be stronger?

[SkipW]

HI Lupin,

You may hear from others with other ideas but here is mine. Since you are limited in the space you have (3-3.5 inches) to land on the sill, you are probably left with notching the joists. If you have the room to add a cleat under the full size portion where they meet the concrete foundation, all the better. This, in my mind anyway, saves you from trying to toenail all of them to the concrete. You just have to attach the cleat. Or I suppose you could use hangers, but I'm thinking of less drilling/fastening into the concrete with the cleat.

the gusset idea would be to add plywood to each side of your married joists, spanning the notched area. This will strengthen the area where the notch would make the joist more prone to cracking/failing. We havent discussed the span, but since you are opening up the whole floor, you will have the luxury of deciding if you want to work with single or double 2 bys to create you floor framing. Also, if you will have the room, a 3/4 subfloor will add some rigidity that might be lacking in the current situation also.

Just some thoughts.....

[Texas_Ranger]

Another way would be lag-bolting a rim joist to the concrete wall and then use joist hangers. You'd need to get creative with the ledge though as the new rim joist would be partially above the straight concrete wall.