[Dan71]

The rim joist and sill plate are rotten and I need to replace them on at least 12 feet. The problem is, I have a 12' x 15' x 6" concrete slab in the way. You guessed it, right above this is a sliding patio door. There doesn't seem to be any flashing or water proofing. It seems that they tried to key in the slab to the rim joist. The scrap of denim is to keep the critters from getting in. The rim joist now has the consistency of mud. These are only 4 of many pics.
Any suggestions? Should I get rid of the slab or try and do it from the inside?
I basically want to do this right and once and for all.

Thanks for your input
Danny

 

[Dan71]

This a quick sketch of the profile of my current set-up.

 

[loneframer]

That right there is about as wrong as I've ever seen that done.

Typically, we will step out every 5th block, 2 coarses down, waterproof the foundation, flash the bejesus out of the exposed wood and excavate a trench in the fill down to the corbelled block for support of the slab.

I don't see any efficient way to repair that without ending up in the same situation in a few years without ripping it out and starting over.

 

[Knucklez]

is it really necessary to connect the slab to the foundation wall? i see that as a most likely problem area.

you may have to cut the concrete slab with a concrete cutter to give yourself some room to get in there with a new rim joists. not sure what to do if there is rebar in your concrete, will this trouble the saw? i just don't see how this could be done from the inside of the house.

Knucklez

 

[Wildie]

I would cut the slab in such a manner that it bisects the Sono tube piers and then break up the concrete between the cut and the house.
Make the repairs to the rim joist and cover it in to prevent moisture from coming in contact with the wood.
Avoid any connection between the concrete work and the house. You may have to put in more piers to support the new cement work.
Another option would be to replace the removed concrete with brickwork.

In either case, make sure of good drainage. Connected to the foundation footing tile, if possible.

 

[Dan71]

Well, you just confirmed what I thought.
My common sense told me it was built wrong, but since I'm not a pro, who am I to argue.
Now I have to get rid of that slab. When in doubt use C4?
Thanks for the comments.

 

[AGWhitehouse]

I would cut the slab in such a manner that it bisects the Sono tube piers and then break up the concrete between the cut and the house.
Make the repairs to the rim joist and cover it in to prevent moisture from coming in contact with the wood.
Avoid any connection between the concrete work and the house. You may have to put in more piers to support the new cement work.
Another option would be to replace the removed concrete with brickwork.

In either case, make sure of good drainage. Connected to the foundation footing tile, if possible.

I agree with this...in addition I would put in membrane flashing along the entire face of the structure to be buried. On top of that place a drainage board (corrugate sheathing would suffice) to allow any moisture along the building face to drain away unimpeded.

 

[Dan71]

I guess I forgot a small yet important detail on my sketch. That is the slab is approximately 48 inches off the finished grade. In this case drainage from ground run off is not the culprit. More likely than not the lack/absence of waterproofing is the problem.

 

[kwikfishron]

Get rid of the slab and build a deck.

When you think you’ve seen everything….and to think that was someone’s great idea at the time.

 

[AGWhitehouse]

Yes, I agree with Kwik. Either put up a deck system or put in some stairs to a grade patio. Sounds like the person who built that had access to some cheap concrete...

 

[SteelToes]

What about...

building a temporary support wall inside the basement and right above on the first floor.
Cutting the damaged section out (joists and sheathing) 1-1/2" past the existing foundation wall.
Pour new concrete and waterproof on the outside.

Ideally you would want to get rid of that slab and build a deck like already suggested but that would involve some massive work. You would have to pull the sheathing off to the nearest “sister” replace the rim board and joists install new sheathing and new flooring + interior walls.

This way you can maybe get away with just cutting the rotted section out…

 

[AGWhitehouse]

You'll need to maintain a minimum bearing depth for the joists and sill plate on that foundation wall.

 

[SteelToes]

You'll need to maintain a minimum bearing depth for the joists and sill plate on that foundation wall.

Of course.
All of that would have to be calculated but it looks feasible to me

 

[Dan71]

I went to City Hall yesterday afternoon and got my permit. The slab is coming down today. Wish me luck!

 

[Dan71]

It fought long and hard, but the slab came down! Darn saw only cuts 5" deep. The slab was 6" and the 1/2" re-bar was in the last inch! The slab never even twitched!!! Went back to the rental store and traded the saw for a jack hammer. Wasted 1/2 a day!! It's all gone now and so is the rotten wood. Thanks for all your comments they were very helpful. Cheers!
Danny