boxes for light fixtures in old house

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  #1  
Old 10-01-01, 03:45 PM
Able Sashweight
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1920's house, brick exterior, lath and plaster interior walls and ceilings. Attic is accessible. Joists are full measure 2 X 4.

The inspector flunked me for rough in inspection, the work including reoplacing 98% of the K&T ith NM. The problem is the lighting fixtures. I want to reuse all of them (replacement is not in the budget). The fixtures were mounted without boxes. Since I touched the wire, he wants boxes.

Here are the cases

1. Outside, surface mounted onto brick walls. The NM comes through a hole in the wall, and would otherwise have been spliced within the spave of the base of the fixtures. I really don't want to chisel big holes in the brick. its an old ourdoor fixture. How can I water seal it? Are fixtures grandfathered?
One lamp is under a covered porch. The other is out in the weather.
2. Surface mount on the ceiling. The old fixtures were wood screwed through the plaster, throuch the lath, and into a 1 X 4 laid flat and bridghing the joists. The 1X4 is parallel to the lath. Not sure how its fastened to the joists or how the lath to it.
A. In one bedroom room there is a paddle fan, and I'd like provision for one in in the other bedroom for the future.
B. The nook has a 10-15 pound chandelier.
C. utility and hall fixtures are light weight.
3. The bath has a surface mount wall mount U channel fixture, with a hollow metal base about 4 X 4 X 3/4". This lamp needs to be centered over the build in medicine cabinet. Alas, there is a stud whose left edge is about at the left edge of the lamp base. So mounting a box to the right of that stud may well through me off center. I dislike notching studs.

Each case may need to be treated differently. Yuck.

Kind of bugs me to
bore a 4 inch hole through a 3 3/4 inch board.
chisel out a hole in brick to hold wires that could be held in the base of the fixture.
chiseling brick at all. Plaster is patchable. brick scars are forever.

Are there thimble sized boxes for the brick problem? Are pancake boxes serviceable here, and how do I handle the wire fill rules?

And how do i deal with cutting a four inch hole through lath of the ceiling? It will weaken the plaster, and I think it will need to be reinforced. How?

Perhaps the best redeeming features are
brick and plaster are not combustible.
The attic is accessible.

Oh, what a pain in the glutimus.

Able
 
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  #2  
Old 10-02-01, 12:17 PM
Wgoodrich
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Able don't panic and keep cool. Your problems are minor and easily cured. First we need to talk options considering boxes then you need to take those options to your electrical inspector and discuss your plans on the boxes you intend to use and ask if he will accept those options as fullfilling his requirements and concerns.




I will copy parts of your posts and then you go look at what you have and can buy.

1. Outside, surface mounted onto brick walls. The NM comes through a hole in the wall, and would otherwise have been spliced within the spave of the base of the fixtures.

REPLY;

You should be able to use a round surface mount box on your round bases. This surface mount box is weather proof with rubber gaskets and can be mounted to your brick. You should slide a piece of PVC conduit into the brick to protect the Romex from abrasions then use a threaded terminal adapter glued to the end of that PVC to screw that PVC to the back of that weather proof box. This can be used where you have more than one Romex entering that outside box. This weather proof box can be painted the color of your fixture or approximate color of your brick. Check this box against your outside fixtures. If these outside fixtures are with round bases often the base of the older fixture will match the diameter of the round weather proof box making a nice looking finished fit.

If you have an outside fixture that has only one wire in it you should be able to use a normal pancake box that will mount to the surface of the brick and the base of the older light fixture should be able to mount over that pancake box using a sealant between the light fixture base and the brick to make a weather proof seal. Only use this option if you have only one Romex entering that pancake box.

There is a trick in the NEC allowing the cone of a fixture to be used in box fill calculations. Check the NEC article number 370-16-A considering the dome of a light fixture. Check with your AHJ to see if you can use this trick adding volume to the pancake box allowing more conductors in that installation. Be aware that the NEC requires that dome to have its cubic inch marked. This may allow your AHJ to say no in using this trick. It is his call.




I really don't want to chisel big holes in the brick. its an old ourdoor fixture. How can I water seal it? Are fixtures grandfathered?
One lamp is under a covered porch. The other is out in the weather.

REPLY;

I hope the reply above gives you enough options to solve your concerns on this questions.




2. Surface mount on the ceiling. The old fixtures were wood screwed through the plaster, throuch the lath, and into a 1 X 4 laid flat and bridghing the joists. The 1X4 is parallel to the lath. Not sure how its fastened to the joists or how the lath to it.

REPLY;

There is what is called a remodel box that you can use cutting a hole fitting that remodle box with wings or madison hangers allowing you to mount a light fixture up to 16 pounds if 8/32 screws are used in that boxes mounting yoke. You again have the option of using a pancake box if you only have one Romex entering that ceiling light box. If you have more you may take the option of mounting a junction in the attic and only running the one switch leg to the light fixture allowing that pancake box to be used.



A. In one bedroom room there is a paddle fan, and I'd like provision for one in in the other bedroom for the future.

REPLY;

Paddle fans require a box approved for the purpose. You must use a box that is marked for use with a paddle fan. These fan boxes come in differents styles from a remodle fan box that you cut a hole through the ceiling fitting the fan box and a rod is inserted through that hole with the fan box attached then the rod is screwed securely into the ceiling joists by stabbing them as your screw. Another fan box is designed to straddle a ceiling joist and is screwed to the ceiling joist by scews and leaving a saddle design around the joist making the round hole of the fan box. Another option is using a pancake box approved as a paddle fan box. These fan boxes come in steel, fiber, or even plastic. The main point of the fan boxes are the mounting nuts holding the 8/32 mounting screws that hold the fan are molded into the back of the box with guides at the surface of the box that obsorb the vibration of the fan so those threads are protected from that vibration that causes failure of the threads of a normal box.



B. The nook has a 10-15 pound chandelier.

A normal remodel light box whether recessed or pancake style should be fine for this fixture the poundage is within the scope of maximum pounds allowed for that normal light box. 410-16 allows normal boxes to support light fixtures up to 50 pounds. If a fixture of fan weighs more than 50 pounds then you must provide adequate additional support.


C. utility and hall fixtures are light weight.

REPLY;

370-27 allows device boxes with 6/32 screws to be used to support a fixture that wieghs 6 pounds or less and is not more than 16" in diameter. These device boxes also come as a remodle flush mount or again you may use pancake boxes if only with one Romex.

3. The bath has a surface mount wall mount U channel fixture, with a hollow metal base about 4 X 4 X 3/4". This lamp needs to be centered over the build in medicine cabinet. Alas, there is a stud whose left edge is about at the left edge of the lamp base. So mounting a box to the right of that stud may well through me off center. I dislike notching studs.

REPLY;

If it were me I would buy a new bath light fixture that has a box built into the fixture allowing a surface mount and flexibility to center over the lavatory.

Others may pipe in with more ideas hopefully to help you.

Hope some of this helps

Wg
 
  #3  
Old 10-02-01, 04:58 PM
Able Sashweight
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Thanks, wg, I needed that.

For the ceiling cases, the existing 1 X 4's seems to be intended for fixture weight support, and may be toenaield in place. If that's the case, then I would remove them if the box support supercedes their function.

Still nervous about cutting 4" holes in lath. Doing that for wall mounted receptacles didn't overly compromise the lath strength. Worried about the strength of the ceiling, cause lath is pretty bendy in the thin dimension. Still, I can find a way to reinforce.

I have yet to see a box volume for my fixture domes. Though not antique, they are generally not recent. One of the outside fixtures has been exposed to the sun long enough to have its glass turned violet: Lots of room in the base, but no markings. Still, I'll look them over.

To be clear - may a pankake box be surface mounted, on either brick or plaster (non-combustible) and without being lidded, fixture mounted over it and mating to the wall/ceiling surface? That's assuming of course that the fixture foot print is big enough to enclose the pancake box.

AS



 
  #4  
Old 10-03-01, 09:43 AM
Wgoodrich
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Yes pancake boxes may be surface mounted with the fixture cone covering that pancake box. Only one Romex may be installed in a pancake box without using the box fill capabilities of your fixture cones. Just call your AHJ and ask if you can use the cone as box fill calculations. If he say yes then you can put more than one Romex per pancake box.

When you cut holes in plaster and lathe use a sideways cutting drill bit. If you use a recipocating saw the vibration often causes damage to the lathe and plaster. They now make a roto tool with a sideways cutting drill bit that acts like a saw blade only is rotary without the vibration causing damage to the plaster. You can also use the sideways cutting bits in a regular drill but the rotation is not near as fast for the cutting speed. Be careful using these sideways cutting drill bits they tend to want to take off on you and cut a wild slice where you didn't plan to cut. Use your thumb against the wall surface as a brake and guide method and be careful. This method of cutting out boxes has become quite popular due to the lack of damage to your plaster and lathe. Lathe does not support the house, only the plaster. Vibration tends to want to separate the plaster from the lathing.

Let us know how you come out

Good Luck

Wg
 
  #5  
Old 10-03-01, 04:43 PM
Able Sashweight
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There are a few new how to questions below, marked with ???. Lots of the rest is thinking out loud.

And in case it matters, my locale still uses 1996 NEC.

Nice tip about side cuting drills. I got good practice with cutting rectangular outlet and switch boxes. Handwork intensive, but I only mangled the plaster in about 3 out of 35. Not sure my methods translat to curved holes, so the roto tip is particularly good. And even a very sharp, carefully applied jigsaw vibrates the lath loose from the plaster.

I think I understand the pancake box well enough to mull over. i gather it must be screwed through to something substantial - is a 1 X 4 laid flat and toe nailed between joists substantial enough? for 6 pound probably. for 30 or 50 pounds? Perhaps I can sister the 1 X 4 with a 2 X 4, and screw them together from below.

Pancake pros:
Lath isn't cut.
cons:
small volume permits only one NM, and requires AHJ acceptance of the dome volume

BTW, NONE of my domes have volumes stamped in them. And none are standard sizes from the table (370-16.a?)

I grock the fan support boxes, and see pancake, eared boxes for fastening directly to joists, and the kinds with adjustable bars for spanning two joists. Here I get nice volumes (like to solve these problems for the longer term), and can see how to place one or the other anywhere in the ceiling, wither with added blocking or by using the adjust-a-bars.

As for the outside, I'm still stumped. Neither was meant to be afixed to a box, though one might attach to a hickey, if I understand what those are (which I may not!).

The wet location has a rectangular back, and is less than 1/2" deep. Pancake is too deep to hide behind it, unless I chisel it into the brick.

The under the porch fixture has a large roughly rectangular base with scalloped edges. Pancake wouon't fit under this one either

Perhaps would be better to remove a brick, split off enough to fit in a 2 X 3 box, and mortar the remainder of the brick back. Then it the fixture onto the surface, over the embedded box, fastening the fixture directly to the brick wall. The AHJ indicated this was ok.

??? Is it legal to surface mount an old lamp fixture to a wall in a wet location (rain exposed), over an electrical box, using Silicone sealant between the flange of the fixture and the wall? (This thing was up there for decades without sealant before).

???Are the rules different for the fixture under the covered porch (is this considered a "damp location")?

???What is a "masonry box" and should I be using one in the brick wall?

AS
 
  #6  
Old 10-11-01, 01:34 PM
Able Sashweight
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Well, the inspector passed my rough work yesterday.

Utility room, with old porcelain base, got a small pancake box cut into the sheetrock. Good fit.

The small hall with accoustical tile over lath (where'd the plaster go?!) got a blue 4/0 box suspended from a metal brace. Flimsy, but easy and adequate.

Nook (funky chandelier), 1st bedroom (celining fan), and 2nd bedroom (pendant, someday probably a ceiling fan) all got solid treatment. 21 cu in metal ceiling fan boxes, side mount ears, and fasted to the joist which was conveniently nearby. Alas, this would sag sideways under weight. So i fit a 2 x 3 high density Douglas Fir cross brace above it, end screwed to the joists with 4 inch deck screws. these i can stand on.

Bath wall mount fixture got a 2 X 4 pressed metal box, side screwed to the stud. It happens to be centered on the mirror. Don't know if that was dump luck or forsight of the builder.

Two outside fixtures go small pancakes, surface mounted. I'll have to cut out some kind of shim, since the boxes at their perimeter are too deep for the fixtures which go back up. But i didn't have to chisel brick, and keep all of my options open.

So it all worked out, except for the ceiling plaster i buggered on the first hole cut.

Someone in this forum suggested that a key skill for electricians is efficient drywall repair. I get to learn plastering.

Thanks for the help!
Able
 
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