This came up in another "homey" forum.

Is the inside of a free standing block wall a "wet location"?

How about the inside of the exterior block wall of a building?

What is the difference?

I have no real opinion. I can make a case either way.

Greg- I think reading the definitions of "wet" and "damp" locations says it pretty well.
There isn't any mention of block wall(s) as being either wet or damp. So I guess they are dry?
My opinion is that a block wall is not a wet location.

Greg:
Is the free standing block wall capped?

Seriously, I have to go along with George. That's twice in two threads!

I do not believe a 'block wall' is always a wet location.

Code does say that a masonry or concrete wall, in contact with the earth - such as a basement wall - is a wet location.

A freestanding wall, such as one that might be built to fence off a patio, would be a wet location IMO.

Additional thought:
Interior side of an outside block wall IMHO is dry, under normal conditions.

Any wiring 'within'/'inside' basement walls in direct contact with earth, by definition is a wet location. Wiring methods on the interior surface should comply with dry locations; or in some instances possibly 'damp locations' due to condensation moisture.

As to a 'free standing' masonry wall, that's a 'judgement' call. George said block is not mentioned in the NEC. Reading ('08) wet locations, I now have to differ with him. 'Block' is IMHO opinion understood to be made of masonry/concrete.

Sorry George, I now only agree with you in one thread.

My opinion (not that you care)

Free standing block wall seperating 2 patios (or the like) outside.Exposed to weather.
Either inside or outside the blocks,capped or not, Wet Location.

I knew this was going to be a split decision. I have also never got a good answer as to why an exterior wall of a house is dry, right up to and including the canopy of a jelly jar luminaire.
I know there is supposed to be a seal between the luminaire and the wall but the bugs I see in them seems to tell me this is far from perfect.
We can't even keep water out of a Bell box.

First of all, I've concluded that Greg is a trouble maker.:) And most of us inspectors are trouble makers.
Hotline1, (John) I looked in the '08 and the wording is the same as the '05 for definitions of "wet" and "damp" locations. I am wrestling with the fact that you claim a slab of concrete and a poured wall are the same thing as a concrete block or a cinder block wall. I have seen block walls that were wet/damp but that's a building issue. I guess like it says in "damp locations", some basements could be considered damp but they are basing that on a concrete poured wall. I look at the hollow core of a block and the fact that the code does not mention block walls and that's why I stake my claim.

Maybe we can disagree on this one:)

Let's open up the question a little.

Can Romex be run inside a block wall at all? Even when the wall is in a 'dry' location?

Article 334 has some interesting twists to this question. First of all, it differentiates between different types of masonry construction. It lumps 'wet' and 'damp' locations together. Perhaps, most importantly, it differentiates between "NMC" and the other typs (NM and NMS).

Mind you, "UF" is none of these, and has its' own section. (A side note: UF can be run in masonry, but not in poured concrete).

What are the differences between NM, NMC, and NMS? I was given to understand that the first is the old cloth-covered stuff, and thet the last has yet to be produced. Is this correct? How can you tell them apart in the field?

334.19(B) specifically allows NM to be installed in the cavities of block walls in normally dry locations.

Basement block walls, freestanding unfinished walls, etc, are not dry. But if the block wall is above ground, covered by a roof, and protected from the weather by siding or brick (etc), then it's a dry area. Why wouldn't romex be allowed in it?

(FYI, 334.2 defines NM, NMC and NMS :))

Typically a block wall will be tar coated (underground), "parged", painted or stuccoed (above ground) and that is the water barrier.
As for NMC, I admit I have never seen it but I understand it has a plastic inner wrapper instead of the brown kraft paper so it won't wick up water. I believe they see this in Canada but I could be wrong. I also have heard it called barn cable.

You tell them apart by the labeling.

When I looked at wire vendors online they send NMC inquiries off to the UF page. With the economies of scale, I really wonder why they would make 3 separate products. The other thing I am seeing UF that looks a lot like NM these days, just without the inner paper liner. The jacket is not much if any heavier. Back in the olden days this was fatter than NM and solid plastic.

Just to play devils' advocate ... is this patio wall 'wet?':

Reno:
Based on the nice graphic, IMHO, the wiring method should be suitable for wet location. Usual install is PVC conduit with THHN/THWN, or UF depending on the 'skills' of the installer.

Masons & landscapers are known to slip in jobs (without permits/inspections) for work like your graphic, with UF stubbed up. Some sleeve UF in the stubs. NMC shows up in HO/DIY jobs occasionally, and would not be acceptable.

Why is it any "wetter" than the wall on the side of the house? Parged block is as weather tight as aluminum/vinyl siding. Since this is detached from the house you would still need a wet location wiring method to get to it so this may not be the best example for the devil to advocate.
Dog leg this over the the corner of the house and feed it from the house wall. Then we have something to debate.

Wall rec: I would say wet. It lacks the over hang of the roof as found on a outside wall of the house.

Patio lighting: wet also,same as a post light,and the rout to get there as stated wet.
RE dog leg to house: as soon as you enter that patio wall, Wet. IMO.

I guess you don't live in a place where it rains sideways.

Wouldn't an unpermeable wall cap be the same as a roof?

snow? 3' deep? does that count? Yes. it rains sideways here too.

Good points. But I will have to go with wet. Logic more than code definations.

How about this - current situation in my home. In one section the basement is separated by a poured concrete wall from an exterior cistern (large 10 x 12 x 8 enclosed water tank) that is full of water. So standing in the basement at that location you are 12 inches away from water that is at a level above your head. The interior basement is finished and completely dry. Finished wall has recepts ect. Is this a wet location?

I actually tend to go the other way, all exterior walls with penetrations to the weather should all be wet, at least at the penetration but that would really turn over the apple cart wouldn't it?
No more Romex to the jelly jar.
The normal installation here is smurf to exterior lamps, sticking out of a hole in the block. The electrician puts in a pancake and installs his light.
They do this to deal with the penetration through the poured concrete cells and tie beam with the other end up in the attic. Usually it gets fished with Romex. I still see the opportunity for water to wick up in the kraft paper wrapper of the Romex and that is supposed to be why Romex is dry only.

In Ann's care there is no penetration to the "wet side" so this is only an issue of the membrane not leaking.

I am currently wiring a 6000 sq ft 3 story house constructed of this material for the interior and exterior walls. AAC Blocks Look at the guy carrying a site made knock out block. Those are very easy for the masons to fabricate on the jobsite. I am running horizontal runs of romex in channels like these, except I am strict that they maintain more than the code allowance of 1-1/4" from the side walls of solid material. The stuff is very easy to work with, provided the masons are of good caliber. The bottom floor of the house is 50 per cent retaining walls so I ran conduit for 100 per cent of the ground floor wiring, but upstairs the wiring is romex. Passed my rough in for ground and second floors last week, no problems. Once I got used to the methods of wiring AAC block houses, I have no problem with running the romex inside the walls in channels we are making for it. The only real technicality I see is I am not really "fishing" the cables between boxes, I am laying them in channels, stapleing them to the bottom of the channel( yes you read right, that is just as easy as putting staples into Georgia Pine) and covering the channel with painter's tape prior to the glue for the next course. They glue these blocks together with something like thin set, not mortar. Its been an interesting job so far.

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.