ECN Forum Forums Code Related Discussion NEC & other Code issues Is a block wall "wet"?

I inspected a kiddie jail in Naples Fl made out of this stuff (Ytong). They used a big router to cut the channels and mortared over them. No Romex, it was EMT.
It turned out to be a problem because in spite of the skim coat of fiber reinforced concrete, the little weasels figured out they could tunnel through it with a spoon. The builder also had a huge problem proving he had enough fire resistance (fire marshal signoff) but the manufacturer finally came up with the testing data.
I have a core I picked up on the job and this stuff floats.

a kiddie jail made out of some sort of floatable cheese Greg?

gotta say, i get some strange calls but......

~S~

I encountered the stuff in the 80's, overseas. It sure looks interesting. As the picture suggests, you can easily pick up a block that, from a short distance, looks like you would need a forklift to move.

The texture is rather rough .... sort of like the scouring blocks restaurants use to clean their griddles. You can very easily cut it, carve it, etc .... often using another piece as your 'tool.' Yet, it has the same compressive strength and fire resistance of 'regular' blocks.

Overseas, it was common to use one of these to make chases for your wires:
http://www.masterwholesale.com/details/1190749723.html

Or, a rotohammer with a chisel bit was used to carve a slot.

The wiring method was similar to our "smurf tube." Slots were simply mortared over.

As I read our NEC, if you did that here, you would need to have 1/8" of steel to protect the wires, as the slots aren't quite deep enough.

In places where the block had to be up first and then channeled, I have been using emt, and then they plaster over it. 2nd floor and up though the masons stop at the second course, which they have made a 3" x 3" channel in the top of it. The channels have been cut extra smooth, unlike what you get trying to make knockout block using regular hollow tile. The dimensions of the wall block is 23-1/2" long, x 10" wide, x 8" high each. There is plenty of space from any outside edge of the blocks to the channels in the middle. I route out for boxes where I want them, and drill a 1-1/8" hole from the channel at an angle down thru the second block to my boxes. A regular router with a wood bit works really good routing out the boxes, takes about 1 minute per box to route. The compressive strength of the block is only about 700 lbs per square inch, so I don't really think this stuff is all that great like they try to hype it. During a hurricaine when the coconuts start flying will be the real test.

As far as fire resistance goes, it is terrific. I have put my propane torch with the 1" tip on a slab about 1" thick for at least a minute or two until it was glowing red. My hand on the backside never felt any heat at all. (Actually I watched the rep demonstrate this for me first before I tried it.) So in that regard, my opinion is it makes a better fireblock than even hollow concrete tile, which transfers the heat around more than this stuff will.

The Ytong came in 8' tall blocks, various lengths as I understand, 8" thick. I didn't get to see how they actually got connected together, that was before I got there. All the power came down from the top.
The structural contractor was very excited about how fast this stuff went up. It came in on a truck, they set it with a crane and he was ready to put the roof framing on it one day.
I had too much electrical stuff to look at to spend much time looking at how this all went together structurally but I am curious. I have to believe they needed some poured concrete, just to get the wind resistance and uplift protection. I bet it was the interior walls that were the "easy" part he was so excited about. I still have to believe the exterior needed a tie beam, solid concrete dowelled columns and corners etc.

Yep, the house has a super structure of metal I-beams that the local building dept required. I agree with them on that, however we are two thirds up and it is coming out really solid I must admit, steel or no steel.