Is it safe to cut a notch in joists and rafters in my attic?

Question

The people who put the electrical system in my house put all the electrical cords over the joists and rafters, instead of using a hole saw to put the cords through the boards. Now that we own the house, we want to put a floor in the attic. So the electrical cords must be placed lower than the surface of the boards so we don't nail through them, and keep the boards flat. My thought is to cut a notch in the boards, just deep enough to lower the electrical cords below the surface. My concern is whether I will weaken the roof support, or cause any other damage to the house by doing this.

Answer 1

due not notch as your rafters will lose strength disconnect the wires if you are able or call a electrician and drill your hole through the center of the rafters

Answer 2

I am not a qualified carpenter or engineer so take this answer for what it is - my experience.
I bought a home that was built in 1925 and had no plumbing. Some time later, probably the 1940s by the looks of pipes and fixtures somebody installed running water. In doing so they notched the ceiling/floor joists. The wood was rough-sawn true 2X4 and 2X6 and was in some cases cut half way through.
The house is still standing after all these years.
It would seem notching a half to 3/4 inch from your joists should have no effect, especially if they are 2X6 or larger and as you will lay a floor over top this will add to the rigidity and strength of the structure.
Before doing any worked check with someone who is qualified to make home repairs and do not simply go on my advice.
As for where to notch joists, I have to disagree with Floyd B. I believe notching along the bottom is the worst place as this is where the most stress is loaded upon the lumber - think of a bow. The last place you want to cut the wood fibers is where the most stress is.

Answer 3

TC...has the most logical answer to your question. For a few reasons. No one can actually see the job at hand, what the span of the joist are( how much load they are bearing),or what condition the attic is in. The type of wood. And the spacing..as in 12",16" ,19.2",or 24" on center? If that attic was not designed for living area...most likely 2x6 joist. or if a rather large span 2x8's could even be 2x10's. If over 15'07" A 2x6 only has a dead load (building material weight of 10lbs squared a foot) and a live load of 30lbs(squared) per foot at a span of little over 11' at 16 on center ( southern pine).
So my suggetion...If it were my home. Either add to the top of the existing joist on top and notch the bottom of the 2x4's for the wires...but the best thing to do...yes, little costly...but the best. Get 2x10 for the area in question...naill them the the existing ceiling joist..and drill threw them...also...use construction grade liquid nails to join the two and also to secure the subfloor, which will also help prevent squeaking later down the road (the plywood(advantec is great, but also a little pricy) Be sure to use a tounge and groove 3/4" subfloor. Screw that down also, nails will back them selves out after time.

Answer 4

Jeanne, there are basically four approaches to this issue:

1. Disconnect the wiring, drill the holes, thread the wires and proceed. The obvious problem is that you've got to cut power to do this, and mess with the junction boxes -or worse: actually cut wire and install the boxes to hold the splices later.

2. Apply firring strips on TOP of the joists, leaving a gap between the wires. This is a bit labor intensive and requires putting the strips everywhere so you have a level surface everywhere. There are also code issues, because now the wire in the gaps is exposed to penetration of screws or nails from above -a "no-no." You can mitigate that exposure by bridging the gap with metal to deflect anything coming through. Of course, you'll need to notch out the strips to the thickness of the metal, so the ends of the metal are not above the top of the strips. The easiest way to do this is to prepare, in advance, some strips of the appropriate thickness with the metal bridge already attached to them -when you come to a wire, just use one of these sections.

3. Notch out the joists to accept the wire, then glue (Liquid Nails) and screw a 2X4 to each side of the joist, below your notch, to restore the strength of the joist. You've got the same code problem as above, so you'll need to put in your metal bridging -in another notch so it fits flush with the top of the joist.

4. Go UP. Install new wiring in the roof trusses and rafters. This assumes that the center section of the ceiling can be made into a flat ceiling as opposed to simply following the pitch of the roof all the way up. You establish the width of the flat part of the ceiling by affixing 2X4's that span the slanted rafters from one side to other and made level. Now, the new wiring can be made to run in the cavity between your ceiling and the roof. In that area, duplicate the wire runs you see below, including junction boxes. There are probably some wires that penetrate the ceiling below your attic floor. For those, you'll need to run wire from your cavity, along the inside of a roof truss, then over (between joists) to the point of penetration. Make sure all runs have PLENTY of extra wire dangling at the ends. Your electrician or contractor can then use those wires to establish new power, and cut away the old wiring.

I hope this helps.

Answer 5

Attic Joist

Answer 6

Don't cut the joists or the rafters. Kill the power to the wires and drill a small hole through the center of the joists. You should not have to go any bigger than a 1/2" hole to get the Romex through it. Rehook the wires and finish the attic.

If you buy or rent a right angle drill it will make the job easier. good luck.

Answer 7

Use furring strips to raise the height of the joists above the wires. You can rip (cut lengthwise) 3/4" plywood into one and a half inch strips for this purpose. Just glue (construction adhesive) and nail the strips to the top of the joists wherever there isn't a wire. When you nail the floor (decking) down be sure to avoid the areas where the wires run. Also lay glue on top of the joists with furring strips before you nail the decking down. (Gluing furring strips will also somewhat strengthen the joists.) You should make sure the joists are strong enough to support a floor based on the span (the length of the joists). 3/4" tongue and groove plywood would be the ideal decking. Hope this helps.
Added: Construction adhesive is never overkill. Too many nails would weaken/split your furring strips. Plenty of glue and less nails for the furring strips. Nail the decking 6" apart on the edges 8-12" in the field (middle of plywood sheets). It would also be more cost effective to rip plywood for furring strips than it would be to purchase the needed amount of strips as 1x3 lumber.

Answer 8

Jeanne B;
The only way myself or anyone else couyld competently provide you with that answer is to actually survey and calculate the ceilings load. It mat seem minor, but those 3/8 to 1/2 inch deep pocket to accomadate the wires could present immediate or a later structural failure; thus I'm going to strongly suggest you not go this route without consulting with an engineer.

There is another way to do this that is much less labor intensive, not to mention safer; but, before I advise you on it I'll need a bit more info concerning the span of these joists and their dimension(s), i.e., 2X10X? or whatever, and what you plan to do with the room. With this info I'll do some load calculations and confer with you further on this project.

I'm not soliciting work; believe me I don't need it; nor am I looking to make any fee here. This is a free site and service; and I participate on it merely to unwind, relax, and to help people out.

Best regards,

Mike Lonergan
TradesProfessional, Inc.
http://www.tradesprofessional.com

Answer 9

While cutting a notch in the top of the joists would be the easiest
It would also be the worst place to put the notch.

It would be best to disconnect the wires, drill holes in the joists & run the wires through the holes. (Make as few & as small as you can.)

I have seen the rules that apply for this but I don't remember them. (I think that you want the holes in the bottom 1/3 of the joist.)

Answer 10

TC's response is appropriate. The only person who can give you a correct answer if a joist or rafter can be drilled or cut without further reinforcing is a structural engineer. Look for architects in the yellow pages and request services.

Answer 11

I don't know for sure if your idea would result in damage ,but I have a suggestion. Why not nail strips on top of the joists that are the same width as the joist's and as thick as the wires and leave gaps to acommodate the wires.