Guest cabin foundation slab

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Old 12-18-15, 03:15 PM
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Guest cabin foundation slab

First, thank you to everyone that contributes here - I've learned so much. This is an incredible forum and place to learn. I didn't find a similar threat to what I'm looking for, but please feel welcome to point me to one if I missed it.

We have a small guest cabin on our property that is about 18' x 16' and I'd like to renovate it. I met the couple that started their family in here. They moved in around 1930. I don't know when it was built though. The main house was built around 1890.

My question is around the slab foundation. The 'cabin' sits to close to the ground and it can rot the sill plate and exterior. I'd like to raise it up to prevent water damage and lower the risk of mice and critters getting in (surprise guests!). I've attempted to take some pictures. What would you do? Pour more concrete on top, start over (close to river so we might infringe on some code), or put it up on a deck like sub floor? We live in the middle of Minnesota. Name:  20151217_163410 (Small).jpg
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Old 12-18-15, 03:30 PM
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Only wisdom I can give is to have you change your profile. You say you live in MN but your profile says MI.
 
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Old 12-18-15, 03:59 PM
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Based on the construction dates, the sill plate should have rotted by now, if it were going to rot, at all. Also, the slab probably doesn't have any footings. You could hire some house movers to lift it so you can add footings & supports, to raise it. I mentioned the lack of footings because cracks could occur, if it hasn't cracked already.

If nothing is rotted or the structure hasn't shifted, I would just renovate from the rim joist upwards.
 
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Old 12-18-15, 04:32 PM
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Not much there left to renovate.
Slab was pored to low, there was no block to get the siding at least 6" above grade.
Doors, siding and windows are poop.
Just not worth saving.
 
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Old 12-18-15, 05:23 PM
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18' x 16' I would not bother with footings and just let it float.
 
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Old 12-18-15, 07:13 PM
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18' x 16' I would not bother with footings and just let it float.
May I ask what size would require footings?
 
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Old 12-19-15, 08:12 AM
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Not really a size thing, but because it is just a guest cabin. In MN I often see detached two car garages (24' x 24') built on floating slabs without issue. Yes, these are permitted jobs with inspections.
 
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Old 12-21-15, 09:35 AM
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So I don't want to be one of those posters you never hear from again. I want to keep you informed what I do here and hopefully it turns out.

Reviewing the wisdom / advice:
1. I probably won't change my profile right now.
2. "Just not worth saving." - It might not be to you, but it is to me. It is a special place with a lot of history and I'm going to try.

Proposal:
From what I've heard, the distance off the ground is important, and the integrity of the foundation. I do already have a rotten sill plate (term? The wood between the studs and the foundation pictured). So here is what I propose:
1. Jack up building
2. Drill / install vertical rebar around edge of slab
3. Install 8" block around edge
4. Place / secure new treated sill plate
5. Place building on new block
6. Landscape away from building
7. Install new gutters

I won't go into everything else, as this is focused on the slab (i.e. siding / sheathing).

This solution brings up the interior floor. I could fill it with something and pour a new floor, but I think I'll do 2x6 or 2x8 decking across and then install a floor. Probably even place insulation down there. I want to do a hardwood on top.

Would you do the interior floor different? Fill it / deck it / step 8" down into it?

Thanks again.
 
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Old 12-21-15, 10:08 AM
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If it were mine, I would not do the wood interior floor option. You would have to be sure the perimeter is waterproof so you don't get moisture between the old slab and the wood floor.

Is the old slab sound? I assume so if you're planning on sitting a course of block on top of it. I would tend to put 4" of compacted gravel over the old slab, then pour a new 4" slab up to the block. Although I have to say, even that makes me a bit nervous, as you run the risk of trapping any water that might get past the outer course of block between the old and new slab. IMHO, the best way would be to hammer out the old slab and pour a new slab that's 6" or so above grade.
 
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Old 12-21-15, 01:18 PM
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That's a good point about the wood floor, and moisture being trapped in there. Thanks for pointing that out.

I'll get started pulling out the old hardwood floor and check the slab condition. Everything else indicates that's in fine condition. But we'll see. I like your gravel fill idea, maybe followed by a vapor barrier. Well, for that point I should do a vapor barrier with whatever solution I do. I'll consider that thanks.
 
 

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