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Mudsill/Floor Joist conundrum

6hresidential | Posted in General Discussion on August 26, 2022 01:07pm

I am working on converting a sunroom into a master bedroom/bathroom and have run into a bit of a conundrum right off the bat. The existing footings have some significant slope to them – one slopes 4″ over 15′, and the other slopes 2 1/2″ over 18′. I know I could double & shim my mudsill, but I’m hesitant to do so because I have concerns about raising the height of the floor and having to deal with transitions with the flooring on the rest of the house. If they could be hidden in door thresholds it would be one thing, but one of these transitions will be right in the middle of a bathroom and that just won’t fly. The current plans call for double 2×6 joists sitting on 2×6 sleepers, and I’ve only got about 7 1/4″ to work with right up next to the house.  So I’m thinking about the two following potential work arounds:
1) scribe the rims and use joist hangers with the original 2×6 joists, and shim between the sleepers 
2) upsize the joists and scribe each of them. I know this would technically void the lumber grading, but this is sitting on a slab…there’s nowhere for these to move. 

Thoughts on these approaches? Any other solutions I haven’t thought of? Thank you in advance for any responses…

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  1. ct_yankee | Aug 27, 2022 10:04am | #1

    Let's consider your major issue:
    "The existing footings have some significant slope to them – one slopes 4″ over 15′, and the other slopes 2 1/2″ over 18′."
    Do you mean footing or top of foundation wall? Why do they slope?
    If they were level after the initial construction of the sunroom, then you my have a foundation issue that won't be solved by scribing the joist to eliminate the slope. Have you checked the top of the framed sunroom walls to see if the same (or similar) slopes exists? If so, then a settling foundation likely exists, which can lead to future problems if the settling is still active (but it will be very slow and not measured in weeks or months).
    (CT Structural Engineer)

  2. 6hresidential | Aug 27, 2022 11:51am | #2

    I mean the top of the foundation wall. The sunroom is gone now, but there didn't appear to be any issues with settling. They used the concrete slab for the floor with some glue down carpet, and the top of the foundation wall is flush with both the slab inside and the sidewalk/patio on the outside, so I suspect it was poured this way intentionally for drainage. The whole sunroom was made with aluminum clad styrofoam, including the roof which was essentially a low slope flat roof.

    1. ct_yankee | Aug 27, 2022 12:19pm | #3

      Sounds like it may have been a patio of sorts before adding the sun room.
      If so, that may complicate things with respect to long-term durability & moisture control.
      It might help if you have a plan sketch showing how this space relates to the original house.

      1. 6hresidential | Aug 27, 2022 12:47pm | #4

        "original house" is a bit of a loose term, as it appears there have been at least two additions. The house was built in the 50s, additions in the 70s, and the sunroom in like 1990. I understand there was also a pool that pre-dated the sun room, so I would say it is likely that the patio (or a patio) also predated the sunroom.

        Here's the exist/demo sketch...the existing laundry room is where the bath is going to be.

  3. User avater
    unclemike42 | Aug 28, 2022 07:38am | #5

    If you trust the slab is not going anywhere,

    You even could use 2x4s as joists, and shim under them to make the floor at the level you desire. Depends on how far apart the sleepers will be, and how far the joists would be expected to span.

    Not sure why the double 2x6 joists. How far apart are you planning to place your sleepers?

    You could make the sleepers treated 2x6 or 2x4, shim between them and your joists, scribe, cut and shim the joists where needed for clearance.

    Having the joint between new and old in the middle of your new bath is worth some effort to tie the floor support structures to each other.

    If you question the stability of the slab, you would be better off breaking it up and taking it out, at least enough for clearance to properly sized and spaced joists.

    1. 6hresidential | Aug 28, 2022 11:51am | #6

      The drawings call for the sleepers to be PT 2x6 spaced 60" OC. I am not sure why the plans called for doubled up 2x6, but that's how the plans came back from the structural review. They also have me placing collar ties on a trussed roof, so I kind of feel like they are just going way overboard to CYA, but I'm not an engineer, so I'm just trying to follow along.

      2x4s is an interesting thought. The "shim" on the one end would be close to another 2x4 though, maybe more. I'll probably end up discussing it with the inspector when he comes out to bless the foundation before I move on to the flooring, but I appreciate all of the feedback...if nothing else it helps me show the inspector thought is going into this!

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