Wiring in block walls?

[tedge]

I'm bidding on 4 bath/shower buildings, all built with concrete block walls. I've never wired anything in block walls, so I'm looking for some guidance. I assume that I would cut a hole into the empty air space in the block and attach a box somehow. For those of you who do this sort of work, how do you attach/secure your boxes? How does one sneak a full length peice of EMT down into the secured box on an outside wall where the roof sheathing is in the way? Any guess as to a percentage of extra time involved as compared to wiring with MC in sheetrock? Thanks in advance.

[brennan]

Are the block wall already up?

[cadpoint]

You have to work in the masons terms, you need to work with them,
usually they will run 4 courses of block a day, they might do other.

A course is 7 5/8" with 3/8" mortor joint *(per ED) X 4 and is usually the SOP.

I've only worked EMT for an approx. 2'-6" length for ease of the brick mason, and tape each end, I've seen higher, but it comes down to working with my the mason, if you work with them they will easily remove a block when you might spot an error, as opposed to long sticking them, JMO.

You'll need deeper mud rings, and don't forget the power for motion paper towel dispensor ...
I'd also duct tape your boxs if they filling the blocks..

[DAWGS]

Install your boxes and conduit as the block goes up. The brick mason will cut the block around your box. Make sure you use masonry boxes. Install your conduit in 3' lengths as the mason runs his block courses. They just lift the block over the conduit, and generally dont want to be lifting blocks more than 3-4'. When you get to the ceiling just 90 stub your conduit out, or offset out of block.

[tedge]

Ok, so it sounds like a lot of wasted time sitting around waiting for the masons. Hmmm... These buildings are very basic, so there's not a lot of boxes to put in. Allthough most will be at the same height, so they'll be done on the same day.

So they generally fill the voids after the blocks are up? That's what holds the boxes in place then? Should I secure them temporarily somehow until the voids are filled?

[SiddMartin]

you could also stub out in the floor and run you conduits in the slab, not sure if applicable though

[fireryan]

They will mud the box in place but its nice if you fill the voids under your boxes with some cardboard or small pieces of block because its easier for them to mud in the box that way. Its best to stay on the masons good side as they can make the job a living hell for you

[fireryan]

If the block walls are already up you can fish a flex down and then mud the boxes in yourself. I have seen some guys use shims to secure the box in place but im not sure how dependable that is? Anyone else do that or not?

[cadpoint]

Ok, so it sounds like a lot of wasted time sitting around waiting for the masons. Hmmm... These buildings are very basic, so there's not a lot of boxes to put in. Allthough most will be at the same height, so they'll be done on the same day.

So they generally fill the voids after the blocks are up? That's what holds the boxes in place then? Should I secure them temporarily somehow until the voids are filled?

Seems you never worked with a mason. To get your conduits to a circuit service point or correct for a run, plus cut your conduits for your boxes. OK say your bored.

With all the extra's of all your circuits all at one elevation, don't be the only one there that hour.

If your good the second conduit can be ready with an offset can be ready to be set in place for them, use math and go with a about a EOC of 10" from box.

[tedge]

The blocks aren't up, it is only at the bidding stage. I'm just trying to get an idea on the work involved so I can make an accurate estimate.

Cadpoint- No I haven't worked w/ a mason before. I see them building chimneys and rock walls, but there's not a lot of block buildings going up in my area. So I should plan on having a couple of guys there to keep ahead of them eh? Pardon my ignorance, but why would I need to make offsets? Couldn't I just come straight down the void w/ my conduit sections into the top of the box? Am I missing something?

[Minuteman]

You won't need offsets with a deep masonry box. Cut your EMT into 3' lengths or so, that way the mason can set blocks over top. Be ready to add another EMT section. Use raintight fittings and wrap them and the boxes with duct tape. Usually, this is something that an apprentice handles. When it's time for another piece, the mason will be sure to call for the apprentice (and raz him a little). :smile:

[wawireguy]

I'd use PVC in the walls to your boxes. Bring a heat gun in case you have to make some bends in your PVC. You can put tie wire through the holes in the back and wrap it around a 6" piece of pvc to hold your box out. You'll want to be there when they grout and hold your box in to make sure the grout doesn't push it out. Put ground pigtails in now in case the back of the box gets grouted.

[480sparky]

Ok, so it sounds like a lot of wasted time sitting around waiting for the masons. Hmmm... These buildings are very basic, so there's not a lot of boxes to put in. Allthough most will be at the same height, so they'll be done on the same day.

So they generally fill the voids after the blocks are up? That's what holds the boxes in place then? Should I secure them temporarily somehow until the voids are filled?

If the brickies are worth their salt, trust me.... you won't be wasting much time. Usually, a good brick crew will be hard to keep up with. And if you don't, they won't have any qualms about going on without you. Plan your box layout, have everything ready to go the day before they start laying block. Msons get paid for laying block, not waiting for the electrician. If you end up ticking the brickies off, you'll end up with mud (mortar), coins or pebbles in your conduit.

As for securing the boxes, most brickies are nice enough to place a scrap chunk of CMU behind your box to wedge it in, then they fill in around the box with mud.

[infinity]

The last bunch of brickies I worked with installed the boxes as the walls went up. They would layout the first course (usually the foreman) on one day and then start the block the next day. After the first course went down we would do our layout on the face of the block. We would also prefab 4 11/16" boxes with connectors, 30" EMT stubs and duct tape over the 2" mud ring. Then we would lay them out at the locations that we had marked on the block. As the courses went up the brickey would cut out a block with his wet saw and mud the prefab boxes right in. After he got up a few courses we would go back and install a 30" piece of EMT. and repeat the process. For several boxes all at the same height we would prefab them together with nipples in between so he could set two or three at a time with only one stub up.

Working well with the brickies can make a huge difference in your production.

[tedge]

So 2" mudrings on 4 11/16 boxes is the way to go huh? I was thinking that the voids wouldn't be big enough for a box that size.

I was told today by the GC I would be working for, that he put in their scope that they were to do the boxes and add the sections of pipe as they went. I just need to have everything on site and laid out. Thanks for all the replies.

[Sonny Boy]

I was told today by the GC I would be working for, that he put in their scope that they were to do the boxes and add the sections of pipe as they went.

That's a BIG NO-NO in Washington State.

[mdshunk]

I was told today by the GC I would be working for, that he put in their scope that they were to do the boxes and add the sections of pipe as they went. I just need to have everything on site and laid out. Thanks for all the replies.That's fine and dandy, in concept, but you really don't want them doing that. Just plan on that language in their scope to more or less assure their cooperation, but you still need to do it yourself.

[wawireguy]

I'd just use masonry boxes or 4 square, deep/shallow w/ deeper mudrings. Want to say 1 1/2"? You should have a variety of boxes on hand to deal with different situations like rebar or other unseen issues.

Another thing you can usually stub out the bottom to if you want to or need to.. Run in the slab or out below grade.

[220/221]

1. Use deep masonary boxes and duct tape the opening.

2. Pre fab all your boxes with connectors and 32"-48" PVC stubs.

3. Install ground screws and pigtails BEFORE installation. It is a helluvalot easir when they are in your hand.

4. Bring donuts for the Brickies.

[infinity]

So 2" mudrings on 4 11/16 boxes is the way to go huh? I was thinking that the voids wouldn't be big enough for a box that size.


Actually it depends on the type of block that they're using. Some block has larger hollow cells than others. This particular job the cell was about 5" wide and the block face about 2" thick so a 4 11/16" box fit like a glove.

[mdshunk]

3. Install ground screws and pigtails BEFORE installation. It is a helluvalot easir when they are in your hand.Yeah, I often wished someone made a 10-32 tap that had a masonry bit tip just for those special occasions when you have mortar oozed into the threaded hole.

[220/221]

Yeah, I often wished someone made a 10-32 tap that had a masonry bit tip just for those special occasions when you have mortar oozed into the threaded hole.

That's why they make self tapping screws :)

Nothing I hate more than crawling down on my knees, looking into a black hole and trying to manuver a ground screw into the back of the recep box. It's a really bad angle for me.

[cadpoint]

The blocks aren't up, it is only at the bidding stage. I'm just trying to get an idea on the work involved so I can make an accurate estimate.

Cadpoint- No I haven't worked w/ a mason before. I see them building chimneys and rock walls, but there's not a lot of block buildings going up in my area. So I should plan on having a couple of guys there to keep ahead of them eh? Pardon my ignorance, but why would I need to make offsets? Couldn't I just come straight down the void w/ my conduit sections into the top of the box? Am I missing something?

Tedge, Sorry if my answer was so cavalier, or stark.

As the reply's started and, & "Well Put All! You'll soon see it just different working with these guys. I can only describe it as working in front of the framer with the sheet rocker waiting, and that doesn't capture the mason's work.

Tape everything, pigtail, and tap you your stubs and fitting, Pvc is cool too. and all said before...

The mason doesn't care about your conduit, its just another rod to them. Beside there might just be reinforcing rods in the mix. We are there just for our service. With filled block, the mason doesn't care to carry your conduit everytime to the device side of the wall, thus the offset. Beside the inside cavity of 6" is a prety big float and an offest sometimes is required.

It's more of a trail by fire for you, and the Mason will show there cards of respect for you, reflective of the respect you show them.

Be ready, don't hold them up, stay out of there way, and you'll do fine. :D

[SiddMartin]

they don't like removing blocks that they just leveled and set because you weren't up on your game and missed one. And they dont' like putting boxes in the center of the block, they'll usually move it 2" either way, this is alright as long as you don't need that box DEAD CENTER, in that case, put a 90 on the box in the side and that will bring ur conduit in channel

[wawireguy]

Speaking of 90's, bring a box of factory 90's or whatever you need to do the job. Bring tie wire. Use PVC for gods sake.. Have different boxes taped with connectors in and ready to go. You might have rebar in the way and have to put in a masonry box or go shallow w/4 square if there is a lot of rebar to the back.

[480sparky]

Another thing to watch for is to make sure you'll clear any steel beams placed above doors. Nothing is worse than finding out the switch box conduit you've carefully installed as the mason 'hop' up is finding out it's going to run smack dab in to the end of a beam. Check the details on the prints carefully, and you may have to offset the conduit a cell or two to clear the beam.

http://i214.photobucket.com/albums/cc172/480sparky/boxbeam.jpg

Look close at the opening on the right of the photo. The red iron beam extends one cell into the wall below, and there's an identical beam in above the gray door frame. That beam extends over the first full cell to the right of the door fram. So if you go straight up from the switch box, you'll run right into it.

[tedge]

Be flexible...Understood...

Of the four buildings I'm bidding, one requires EMT in the walls, and the others allow PVC. In either case, I'll take MDSHUNK's advice and be on-site to make sure it is right.

None of the buildings are very big, so I'd imagine they'll put them up in 3-4 days.

[480sparky]

Having a fully-charged sawzall on hand really helps, too. If you're running EMT, you can just hang your bender on the scaffold somewhere handy. Just stay out of the masons' way until it's time for you to do something.

Another tip: When you put the last straight piece of conduit on, take a quick measurement from the top of the brick to the top of the conduit. Then, as you're back out of their way, calculate how long the 90° needs to be to come out of the wall at a mortar joint. Brickies love you doing that... they can just take their brick hammer and notch the brick by hand. If your pipe comes out somewhere else, they tend to get grouchy.