Replacing a pocket joist

[Dan McGonigle]

I’m starting to address some of the sagging floors in our 1842 brick house. The worst offender is a front corner, where the floor slopes down probably about 3” over 8 feet or so. The supporting joist fits into brick pockets, one at the front of the house, one in a chimney support. The span is only about 7 feet. This joist was clearly replaced previously, it’s 2 2x12, not laminated together because they appear to move free from one another. I’d like to replace this joist. I started jacking it up yesterday, moved it up about an inch. I’d like to jack it up, provide temporary support of the floor, remove the joist and inspect/repair the brick pockets, then install a new joist. I won’t be able simply install a new full length joist from below the floor because they slide into the pockets a few inches. Anyone have any tips? I’ve seen talk about installing 2 piece joists, sistered to another joist or plywood, bolted, glued, etc.

[Tom M King]

I'll see if I can find a picture. I'd make a sheetmetal thing to fill the "mortise" in the brick, so the wood is not resting right on the masonry. Sister, and bolting is fine.

[Lee Schierer]

If the 2 x12's aren't damaged why replace them? Simply jack them up, do your repair and shim under them so they stay at the proper level. Use non-compressible shims so you get the true height you are after. You can bolt them together if you feel it is necessary, but a 7 foot span shouldn't require that.

[Dan McGonigle]

The one end does appear to be a little damaged. Unfortunately, it looks like the end was notched to fit into the pocket, as the width of the joist is greater than the height of the pocket. So I cant get a good look at the pocket, or shim it for that matter, without removing the joist.

[Malcolm McLeod]

If the 2 x12's aren't damaged why replace them? Simply jack them up, do your repair and shim under them so they stay at the proper level. Use non-compressible shims so you get the true height you are after. You can bolt them together if you feel it is necessary, but a 7 foot span shouldn't require that.

The one end does appear to be a little damaged. Unfortunately, it looks like the end was notched to fit into the pocket, as the width of the joist is greater than the height of the pocket. So I cant get a good look at the pocket, or shim it for that matter, without removing the joist.

Do a little research on how to do a "Fireman's cut". For joists installed in a brick pocket, the end should be relieved, so that in a fire, when the joist(s) burn(s) thru and give(s) way, it doesn't lever out the pocket and collapse the wall - - and kill all the fireman, on whom the wall falls.

(Guess I should indicate why I included Capt. Shierer's shim quote)... Shimming under them could push the joist up into the upper brick and obviate the relief cut.

[Malcolm McLeod]

... I won’t be able simply install a new full length joist from below the floor because they slide into the pockets a few inches. Anyone have any tips? I’ve seen talk about installing 2 piece joists, sistered to another joist or plywood, bolted, glued, etc.

Just revisiting this, and recalled a bit of an old episode of This Old House. They were replacing joists in a brick pocket; all 'full' length. But if memory serves, the joist pocket was deep and wide enough (on one end, at least) to place a joist at a slight angle and 'over-insert' it, then align the opposite end to its pocket and insert that end - pulling some out of the first end's pocket and providing sufficient support at both ends. This might require a couple of iterations to sneak up on the required length? (I think this may also be where I first heard of a "Fireman's Cut"?)

...Apparently, builders of that era were advanced enough to think long term.

[lowell holmes]

I would also glue the new boards to the existing joist.

[Tom Bender]

You can cut a little more of the end off to give you better access. If it is notched say 3", you can taper this back over say 6". Just don't extend the 3" straight portion.

[Bruce Wrenn]

Could you have a piece of 1/8" steel cut to shape of joists? You can flex it enough to get in both pockets. Pre drill it, and sister it next to joist that has been cut so as to fit in one pocket and scab another joist on other side that's just short enough to fit in one pocket, and just clear the other pocket. Bolt it up, with bolts spaced towards both top and bottom. Most likely, you could use the steel and two pieces of 3/4 plywood to replace the joist. Because of limited nailing space, I would pocket screw the floor down from bottom.