Replacing too-short joists after mud bed removal


Old 01-02-14, 07:24 PM
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Replacing too-short joists after mud bed removal

Remodeling 2nd floor bath in 88 year old house. I am drawing up my plans for my structural permit and wanted to run one aspect by the experts here first.

After removing all plaster, lath, and 2" mud bed I can see several problems with studs and joists. Every single joist is either way over notched, cut entirely, missing, or simply not supported at all. (fwiw, the install of the massive cast iron stack and fittings is the cause for a lot of this. I have vacillated between replacing it, then had a plumber convince me it is in pretty good shape, but now I see the structural problems and am back to removing it.)

I'm pretty clear on how I can repair it all except for one aspect. The house is divided into three parts structurally with joists spanning each of the three sections as shown below. The bath being remodeled sits over the middle section.

| -------- 11.5' -------- | --- 7.5' --- | -------- 11.5' -------- |

When the house was originally built, it appears the joists under the bathroom floor were originally 2x8 (all other joists in the house are 2x8). Somewhere along the way, these were replaced (or cut down) to be 2x6 in order to create the 2" mud bed. So originally the left wall of the bathroom was supported by the left section and middle section joists , and the right wall of the bathroom was supported by the middle section and right section joists. But now, the middle section joists are too short to provide any support for the bathroom walls (which in turn support joists in the attic). So I either want to replace these short joists with 2x8 joists.

My concern is - will I be able to get the new joists into place without jacking up the walls?

One more bit of info - the shoe doesn't rest directly on the existing 2x8 joists - there is actually a layer of 1/2 inch wood floor separating the joists and the shoe. I'm wondering if I can remove a portion of this flooring in order to get the new joists into place, and then pound in a new piece of wood between the new joist and shoe.

A pic is attached showing what I am referring to.

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Old 01-02-14, 09:21 PM
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One thing that will work in your favor is that new 2x8's are usually only about 7 1/4" wide. One bit of advice I would give is probably to leave as much existing framing as it is reasonable to leave, and sister new framing onto the side of it. Being smaller dimension, you might get lucky and will be able to lay them alongside (flat) then roll them in place. If not, the usual trick is to chamfer one or two corners of the new joist just slightly to provide enough clearance that it will help it roll into place. I don't know that we can provide more advice than that.

I would leave the subfloor intact, hoping that you can roll joists into place as mentioned above. What you are calling "shoe" is more commonly referred to as a plate. (interchangeably: bottom plate or sole plate while sill plate usually refers to the one that sits on the foundation). Shoe is kind of colloquial.

I've seen bathrooms where they have done that exact thing with the mortar floors and the hacked joists. What a mess!
Old 01-03-14, 05:21 AM
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If you pull back on your picture to include a wider look at the area, I think you will get more people on board to offer suggestions. I have a general picture of your room, but need better bearings and a suggested layout relative to the floor joists and any new/removed walls resulting from the remodel. A couple of wide angle pictures and a schematic would help.
Old 01-03-14, 10:18 AM
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Thank you very much for the responses - the advice and corrections on terminology are much appreciated. I plan to use the below as the basis for my plans when applying for my permit. I have obtained (prescriptive) permits for electrical and plumbing, but this will be my first building permit. Any advice along those lines would be much appreciated as well.

Turns out the joists in place in this 1927 home actually do measure 2 x 7.25. Which is good news from the standpoint of support because new joists will match, but it does mean I will need to chamfer the edge so I can roll them into place (thank you so much for that piece of advice!).

My plan is to:
  1. Remove the stack and all plumbing.
  2. Sister 2x6 along side all studs in order to restore support, and to maintain space for use as a “wet wall”.
  3. Sister 2x8 along side all joists in order to restore needed support and to raise the floor back to original level. Will chamfer and roll new joists into place. Will glue and nail to existing joists. Of course, add the one joist back that was removed.
  4. Replace stack, with tub drain running down to basement, then connected into stack in the basement.
  5. Replace sink drain by running through holes in 1/3 end of newly sistered joists, then down entryway wall, then connected into stack in the basement.
  6. Vent Sink and Tub into stack up through attic.
  7. Lay 3/x subfloor (to match existing subfloor height in adjoining rooms), then lay Ditra and tile.

The pic below shows the first floor entry way (top left), 2nd floor bath (bottom left), and a composite of the two (right). The entry way has a door in the middle, and leads to the foyer. There are doors on either side – the left goes to the living room and the right goes to the dining room.

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The top two pics below show the bathroom wall (both from inside the bathroom and from the hall outside the bathroom). The bottom left pic shows the view looking into the entry way from the foyer. The bottom right pic shows the sink drain that is running from the bathroom wall, over the entry way wall and to the stack.

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The pic below shows several areas of concern – every single joist has either been notched (for the sink drain and/or K&T), unsupported, or removed entirely. Scrap pieces of wood has been used for supports and shims.

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This pic shows the sink drain from both above and below. Note the “supports” nailed to the 2x8 to support the lowered floor in the bathroom.

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This shows the stack from within the entryway. This one topped them all for me – they used the lip of the stack to support a piece of 2x4, toe nailed the other side, and then placed another 2x4 on top of that. From the other pics, you can see where they used a 2x4 on edge with shims over the entryway wall for additional supports.

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Old 01-04-14, 08:46 AM
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I can guide you with proper plumbing, but would need some type of diagram of whats there now pipe wise and what you want to do. List all baths, sinks, etc that tie into the stack.
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