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We just had a roofer install a skylight on our sloped ceiling of our third floor. (The third floor is basically a finished attic in the peak of the roof.) The installer just cut away two rafters (16 inches apart) in order to fit in the skylight. He did not install any headers on these cut rafters.

I asked him about it since I thought you should always put headers on when you cut like that but he said it was fine to leave it without headers. He's a roofer so I thought he must know and I didn't argue, but now I can't stop thinking that this is not right. I was surprised actually that the rafters are only two by fours. Our house is over a 100 years old.

Any advice, please?

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isherwood
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concerned in Toronto
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    Would ask that roofer to come back and jump up and down on those two rafters. Then ask if he still thinks it is okay. – crip659 Apr 07 '23 at 17:34
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    Clearly a case for Mike Holmes. When you say "rafters . . . 16 inches apart" do you mean the structural members under the roof decking? Or do you mean the structural members holding the ceiling of the living space? – Jim Stewart Apr 07 '23 at 17:50
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    These are structural members right under the roof decking. The drywall for the sloped ceiling is attached to these same 2 x 4's. There are no other 'members.' – concerned in Toronto Apr 07 '23 at 18:13

1 Answers1

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We could use more detail about the roof framing for confident answers, but here are some thoughts.

  • A house that old has a few things going for it. One is heavy, old-growth lumber. Another is heavy roof decking (probably 7/8" thick solid wood boards 8-14" wide). Yet another is beefy nails. For that reason, the roof as a system is probably still ok.

  • Yes, I would've headed off those rafters. There's stress on them in one direction or another, depending on overall framing design, and that should be managed to avoid sagging, etc.

  • No, roofers don't necessarily know (or care). They're in a square-foot-per-hour business with thin margins. Any delay could cost them their entire profit margin. Therefore, delays and distractions are minimized. This might be a reason to hire a carpenter who knows some roofing rather than the inverse for this job.

  • Many rafters are still "only 2x4s", even with engineered trusses of considerable span. They do the job perfectly well when used properly. My guess is that your attic has 1x4 webbing in several locations on each rafter reducing local spans.

At this point I'd get a good look into the attic and take a walk on the roof. I'd want to know the exact framing strategy and what the deck feels like under load. There may be repair to be done.

Update after new information... The solution here is fairly simple, I think. Open the drywall and install double 2x4 headers between the adjacent rafters using suitable joist hangers. Just toenailing the headers in place doesn't provide enough shear support, in my opinion. It might be ok if 4 nails can be driven from the outside face of the rafters, though. Still, hangers are dirt cheap.

isherwood
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  • Thanks for your helpful reply. Unfortunately there's no way we're going to go up and walk on this roof. It's steeply sloped and difficult to access. We also can't take a 'good look' into the attic since there really is no attic, the drywall is on the rafters, creating the living space on the third floor. I think I will contact the roofer and try to get them to install headers. The work was just done yesterday and I haven't paid them yet! – concerned in Toronto Apr 07 '23 at 18:38
  • Ah, so it's a hot roof. That should be in your question. – isherwood Apr 07 '23 at 18:39
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    It’s good you haven’t paid. Continue to not pay until this is resolved to your satisfaction. The only circumstance I can imagine where this would be acceptable is if there were purlins (perpendicular beams underneath the rafters) very close to the top and bottom of the new hole. Don’t hesitate to threaten with the possibility of building inspectors. – Aloysius Defenestrate Apr 07 '23 at 19:02
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    You don't think it's necessary to double up on the rafters on either side of the opening? The ones to which the headers are going to be fastened? I assume OP is in Toronto from his name, so snow loading would be a concern. – SteveSh Apr 07 '23 at 19:53
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    Given what I said about the old-school framing, not really. The decking adds a lot of strength. I kinda doubt that's practically feasible anyway. – isherwood Apr 07 '23 at 20:00
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    isherwood thank you for the joist hanger suggestion. I was thinking they'd just toe-nail which wouldn't be ideal but joist hangers solves that problem. – concerned in Toronto Apr 07 '23 at 20:24
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    Simpson Strong Tie offers screws for some connectors. Would those be easier to use and less likely to jar loose drywall? Does the OP need joist hangers or simplly corner angles? – Jim Stewart Apr 07 '23 at 22:11
  • Actually, in thinking about it, I don't see how joist hangers can work. The header will be two 2X4's lying flat, butting up against the vertical rafter which is 4 inches wide, so it's 4 inches against 4 inches. I think corner angles might be the answer @Jim Stewart. – concerned in Toronto Apr 07 '23 at 22:22
  • Simpson LUS24-2 hangers are what you want here. A real lumberyard will at least be able to order them in, if not have them in stock. – Aloysius Defenestrate Apr 07 '23 at 23:12
  • I don't see how the Simpson LUS24-2 hangers will work. They would have to be lying on their side in order to be able to screw them into the vertical rafter--the 2X4's are lying flat so they will not be 'hanging' in the hanger. So it makes more sense to use corner angles like the Simpson Strong-Tie ZMAX Galvanized Angle – concerned in Toronto Apr 08 '23 at 13:16
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    Installing a header here means two different connections--one is the header to the cut ends of the rafters, the other is the connections of the ends of the header to the sides of the uncut rafters. Looks like hangers would work and maybe be best. Angle connectors might also work. This is a decision for an experienced framer or engineer. – Jim Stewart Apr 08 '23 at 15:09
  • I don't know why you say "still" only 2x4. Older construction was based on the idea that certain size members can be used in certain applications without having to perform load calculations, while newer construction uses load calculations to allow the use of minimal-cost members. I'd be more worried about cutting one 2x4 than about cutting a pair of adjacent 2x12s, since construction using 2x12s is likely to have stronger roof decking than one using 2x4s. – supercat Apr 08 '23 at 16:05
  • Another possibility for fastening headers in this case is long structural screws which are designed for retrofit connections, e.g., retrofitting uplift resistant connections between rafter ends and top plates. With the skylight already in place it might be difficult or impossible to fasten the headers using standard joist hangers. I think Simpson makes such screws. One thing though would be to cut the stringer length to be a good fit but not so tight that forcing it in would distort the box of the skylight, and not so loose that tightening the screws would distort it. – Jim Stewart Apr 08 '23 at 17:36
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    Avoid a hasty "improvement" to this installation that might make it leak or damage it. – Jim Stewart Apr 08 '23 at 18:00