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Discussion Starter · #1 ·
Original owner enclosed an outdoor porch. They put wall bottom plate directly on porch slab then built up interior slab by 1/5 inches so it is level with house slab. Of course bottom plate is rotting out and I need to replace. Soooo, I need to extend the interior slab out about 5 inches to support a new bottom plate, but it will only be about 1.5 inches thick. What is a good way to do this? With it only being 1.5 inches thick can I even drill and put in rebar to existing slab? Not sure if drill is too wide to directly drill into existing slab without going in at a good angle.
 

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retired framer
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Original owner enclosed an outdoor porch. They put wall bottom plate directly on porch slab then built up interior slab by 1/5 inches so it is level with house slab. Of course bottom plate is rotting out and I need to replace. Soooo, I need to extend the interior slab out about 5 inches to support a new bottom plate, but it will only be about 1.5 inches thick. What is a good way to do this? With it only being 1.5 inches thick can I even drill and put in rebar to existing slab? Not sure if drill is too wide to directly drill into existing slab without going in at a good angle.
Why not treated lumber?
 

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Discussion Starter · #3 ·
Thanks NealTW, that may be an option but I am worried that even over time the pressure treated wood will rot at the lower elevation where water will pool during the spring rain season. I was going to use pressure treated wood regardless for the bottom plate but was still trying to raise it above the porch level where water might pool. Might be overkill but would love some feedback on how long the pressure treated wood might last where there might be rain pooling.
 

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JUSTA MEMBER
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Brick it.

Using common brick as your material, use PL Construction adhesive to anchor the bricks to the pad and riser.

Make sure that you clean out all debris, and that it is dry, then but a bead of adhesive in the corner, and close to the outer edge, and use a rubber hammer to TAP the bricks in.

They will raise your floor to the right height, then place your bottom plate on the brick.

Common brick are 1.5 thick X 3.5 wide and almost 6" long.


ED
 

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retired framer
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Thanks NealTW, that may be an option but I am worried that even over time the pressure treated wood will rot at the lower elevation where water will pool during the spring rain season. I was going to use pressure treated wood regardless for the bottom plate but was still trying to raise it above the porch level where water might pool. Might be overkill but would love some feedback on how long the pressure treated wood might last where there might be rain pooling.
No matter what you do water proofing is still a problem.
Do it the easiest way and water proof it and then use a PVC trim at the bottom so water won't hurt it either.

Bakor makes a spray primer that helps peel and stick, stick to concrete.


 

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Naildriver
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1 1/2" thick concrete will not support a load bearing wall. You need to dig footers and pour concrete for proper support. Not sure if that is what you are looking to do or not.
 
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newbies always do this - ask ?s anticipating support for their theorized answers then leave us in the dark re where THEIR 'WHERE' is,,, htf're we to answer when we don't know 'WHERE',,, & who, in their right mind, thinks 1 1/2" conc's going to support any load at all,,, hell, it'll crack just on its own w/o a butterfly landing on it
 

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retired framer
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Guys, you have to read the fine print.

The rotted sill plate was on the the original slab. Then the concrete was over poured to being it up to height. So this 1 1/2" is filler between the plate and slab.
 

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Hammered Thumb
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This is a typical scenario, one owner encloses a patio/porch, the next insulates and puts electric, the next replaces with nice windows and carpets, the last has to deal with problems. At least your walls are probably only bearing their own weight, but who knows about the roof support having a proper foundation. Probably a 3 1/2" patio slab at best, with level grade, so you will never stop ponding. But you should really try to get the grade lower, I imagine you'll never get 4"-8" below though. So . . . it doesn't matter about raising the old sill plate, you'll still have issues, so just replace it with a double plate and put a membrane outside like the photo above.

If you really want to shim, "common" brick just differentiates it from "face" brick. What is important is an ASTM C90 designation, which specifies load-bearing capabilities. Very few, if any, bricks at the big box will be that, especially not pavers. Either a 2 1/4" high CMU ("common brick size" or "structural brick"), or a 2" nominal (1 5/8" actual used as a soap) CMU would be better. You'll have to fasten the wood sill through this shim to the slab to prevent wall kickout, but again, all this trouble of mortar, drilling for anchors in a 3 1/2" slab and shim, and membrane doesn't get you anywhere better if you can't lower the grade.
 

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Naildriver
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Guys, you have to read the fine print.
but it will only be about 1.5 inches thick.
IT don't matter. That 1 1/2" of concrete will break, crack, degrade and poop on itself once a load bearing wall is placed on it. Form it up, pour it, but make accommodations for footers for the load bearing part. I doubt this slab is more than 3 or 4".
 

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retired framer
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IT don't matter. That 1 1/2" of concrete will break, crack, degrade and poop on itself once a load bearing wall is placed on it. Form it up, pour it, but make accommodations for footers for the load bearing part. I doubt this slab is more than 3 or 4".
I agree with the 1 1/2" not being a good idea, I don't think the slab is problem, its' been there long enough for the plate to rot. So the weight isn't even spread evenly on the slab. I still say just replace the wood.
 

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Naildriver
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Agree, replace the wood with additional preservative and possibly some sill seal, or other sealant to keep it away from the concrete as long as possible. But I would not add 1 1/2" of concrete.
 

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Concrete & Masonry
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1 1/2" thick concrete will not support a load bearing wall. You need to dig footers and pour concrete for proper support. Not sure if that is what you are looking to do or not.
If it's 1.5" thick concrete block fully bedded over a stoop, then it certainly won't be an issue. A 4" thick or 8" thick concrete block isn't any stronger than (actually weaker in most scenarios) a patio block in compression.

That said, I'd probably lay a 4" (half course) block in it's place to get above grade, and cut the bottom of the wall/floor joists as necessary to accommodate the extra curb.
 

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Naildriver
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If it's 1.5" thick concrete block fully bedded over a stoop
How does that work? The OP mentioned "load bearing", so I am going from that. If there is a substantial roof system with a load, 1 1/2" of additional concrete poured to make up for the drop won't stand up, nor will a concrete block. I believe I read that this was an embedded piece of wood to which concrete was poured on the inside. Once the plate was removed, it left a 1 1/2" void on the outside of the original pour.
 

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Naildriver
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But you are talking about balancing an 8x16" block on a space only probably 3 1/2" wide along the length of the patio. It is where he had a bottom plate rot out, but not before concrete was poured against it, leaving the impression of the plate.

Y'all correct me if I am wrong, but that is what I am reading into it.
 

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JUSTA MEMBER
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But you are talking about balancing an 8x16" block on a space only probably 3 1/2" wide along the length of the patio. It is where he had a bottom plate rot out, but not before concrete was poured against it, leaving the impression of the plate.

Y'all correct me if I am wrong, but that is what I am reading into it.
I read it as the concrete was poured inside the room, level with the bottom plate, only on the inside.

Leaving just one 1.5" rise, after the plate rotted, and being removed.

Not a 3.5" groove.

We do need a picture to accurately say though.


ED
 
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