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Housecrzy 09-29-2012 04:27 PM

What to do with walls built on open cinderblock
My wife and I could use a little help.
Our 2 story home is constructed on a poured slab and is 1680 sq ft.
The first floor 28x36 with a 1 car garage 10x28 (no basement). Second floor is 28x24. I discovered yesterday that the outside bearing walls are cinder block even with the height of the slab. The bottom plate is 2x4 and in direct contact (no termite shield no vapor barrier) with the open cinder block. Dirt is inside about 10" down. You can literally smell damp earth when I opened the drywall up. There is a 3/4" gap between the 2x4 plate and the slab that is open to the core of the block. We became aware of this because a snake got in to the dining room from this back corner. I assume this was a popular construction method in 1974? The slab in this left rear corner also sounds very hollow when you tap it. We are installing a patio door in this corner of the home. My plan is to fill the open cells of the cinder block with concrete. Would it be wise to drill a hole in the slab and pour or pump some type of grout or concrete into the hollow souding section, any suggestions would be apreciated.

The patio door is standard 72x80 and am installing it approx 22" from the corner of the house with a standard 2x12x75" header

GBrackins 09-29-2012 07:00 PM

if possible could you post a few photos?

joecaption 09-29-2012 08:33 PM

Ha that's my line GB. lol

Housecrzy 09-29-2012 08:45 PM

3 photos
3 Attachment(s)
First photo left corner.
Second shows pry bar in cinderblock with concrete slab with tack strip to the left of it and 2x4 wall plate resting on cinderblock'
Third photo is somehow reversed but is a close up of tack strip on cocrete slab at top of photo 3/4" space and 2x4 on cinderblock.
Hope this helps.

GBrackins 09-29-2012 08:54 PM


Originally Posted by joecaption (Post 1020216)
Ha that's my line GB. lol

sorry joe didn't see you on ..... :)

GBrackins 09-29-2012 08:57 PM

so it sounds like you have a foundation wall made from concrete slab, and a concrete slab that is level with the top of the blocks. how is the sill plate attached to the blocks, or is it?

Housecrzy 09-29-2012 09:06 PM

Single j-bolt
There appears to be a j-bolt in the corner(it can be seen if you look close at first photo second 2x4 bay from left) but does not have a washer or nut on it. It seems as if it were for alignment only as there are no tie downs other than that. At least in this 10'section.

GBrackins 09-29-2012 09:15 PM


Originally Posted by Housecrzy (Post 1020063)
The bottom plate is 2x4 and in direct contact (no termite shield no vapor barrier) with the open cinder block. Dirt is inside about 10" down.

not sure I'm following this comment about the dirt is inside about 10" down, do you mean there is nothing under the concrete slab?

Housecrzy 09-29-2012 09:20 PM

There is dirt inside the hollow cinderblocks where the prybar is inserted (second photo) House walls are built on hollow cinderblocks that are on perimeter of poured concrete.

GBrackins 09-29-2012 09:45 PM

I'm trying to figure out what would be gained by filling the cells of the block, not saying its a bad idea. after all I'm sure the rest of the house is the same. If you have the time and want to fill the cells I do not see an issue but with a slab over them it may be a lot of work with no gain.

I would certainly seal the gap between the slab and the wall, maybe with a spray foam product to keep moisture and vapor from entering your home.

is your carpeting laid directly on the concrete slab?

hopefully other members will chime in with their thoughts ....... btw, where are you located?

Housecrzy 09-29-2012 09:57 PM

The moisture entering the wall space is creating a problem. We can now see the horizontal joints in the middle of the drywall(in some spots). I believe the moisture is actually softening the drywall in these areas. Also where the patio door will sit, I must fill the voids in the cinderblock to seal it. Yes the carpet and pad are installed directly on slab. Lastly the poured slab in corner sounds as though there is a void below it.

GBrackins 09-29-2012 10:04 PM

the space where the moisture is entering is through the 3/4" gap between the slab and wall?

how is your carpet attached, is on the slab?

Housecrzy 09-29-2012 10:18 PM

It looks like the cinderblock was used as the form for the slab it does not cover the cinderblock at all. Because the 2x4's sit directly on the open cells of the cinderblock I believe moisture is wicking into the wall because it sits on it with no moisture barrier or termite shield.

Wildie 09-29-2012 10:56 PM

Its likely that a footing was poured and then the block wall was installed on the footing.
Then the slab was poured inside the blocks, in the same manner as one would pour a basement floor.
This block wall should have been parged and water proofed on the outside.
If it hasn't been waterproofed, you should excavate around the outside perimeter and do so.
Just filling the cavities in block will not be sufficient as moisture will leach in and become rancid.

joecaption 09-30-2012 07:00 AM

Is that Cellotex on the outside walls? (it's a black fiberboard sheathing, you can just stick a nail in it like a thumb tack)

Is that bottom plate pressure treated?

What is that white stuff all over the wood and sheathing (sure looks like mold to me)

How close to the grade is the siding on the outside of this building?

Keep in mind were not there and all we can see is your pictures, but what I'm seeing is no wood sheathing in the outside corners for shear strength.
Sure looks like some form of fungus on that wall to me.
No termite shield. (would not do any good anyway, the way that was built because the blocks were not filled as they should have been so the termites can just go around it)
Lack of back filled voids for foundation bolts. (should have been one within 2' in each corner and others along each wall.)
Looks like no pressure treated bottom plate.

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