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Hip roof support

Hip roof support

Hip roof support

(OP)
Looking at a brick ranch built in the 70's, the roof is hip with a ridge board, house is L shape configuration.So 2 ridge boards and each board has a 2x4 a couple feet from the end, nailed to the side of the ridge board and toe nailed into the top of the wall or ceiling joist. These 2x4's have pushed the sheeting up an inch or so, not sure how many years it has been like this, but should these have been removed when the sheeting was installed? How much movement is normally realized during loading?

RE: Hip roof support

No way to answer that without a whole lot more structural information about the building.

Mike McCann, PE, SE (WA)


RE: Hip roof support

(OP)
Let me know what info you need.

RE: Hip roof support

Do you have a roof plan and a section?

Dik

RE: Hip roof support

If the 2x4's are oriented vertically, they are probably creating the necessary heel height and transferring the hip rafter reaction to bearing. And, by the sound of it, the rafter to 2x4 connection may be giving way allowing the roof to settle around the 2x4. At least that's my best guess based on the information provided so far. I'd recommend posting a sketch of the framing plan in this area as well as a detail sketch of the particular condition that concerns you.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Hip roof support

The L shape description suggests that the ceiling joists and roof rafters are not all align in a favorable way (to provide tension anchorage of the rafter tails).
I suspect (as does KootK I think) that the ridge line (and resulting rafters) are dropping.
Often, the 2x4 props were used to provide temporary support (to align things) and in one sense maybe they could/should have been removed but usually they are simply left in place.
The "problem" that I usually find is that the remaining structural components are not truly capable of safely supporting the code required loading.
Roof plan and/or photos will be helpful.

RE: Hip roof support

Quote (HouseBoy)

as does KootK I think

Yessir.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Hip roof support

I have never seen a 40 year old brick ranch with a hip roof that has not begin to sag. They require support at the hip/ridge and also usually at mid-span on the hip.
I rarely see problems with similar high-pitch hip roofs

RE: Hip roof support

(OP)
I will take some photos and upload.

RE: Hip roof support

(OP)
do these photos help?

RE: Hip roof support

They help me to realize that my initial comments were off target. From what I see, it looks as though the 2x4 may indeed have been installed as a temporary support that probably ought to have been subsequently removed.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Hip roof support

Perhaps it was intended to be temporary but it the roof is "sinking" so... the remaining roof framing is not performing suitably with or with out the extra prop in place.
"L" shaped plans with hip roofs that are stick framed without structural ridges are not likely to work.
When I come across them, I often find that "internal ridges" installed in the attic space can be an effective solution. Although, you want to install that framing in the morning!

RE: Hip roof support

(OP)
Did these photos help?

RE: Hip roof support

Yes they help to confirm my (and other's) suspicions.

It's probably not as simple as taking out the 2x4's (that have pushed up the sheathing).

Realistically, stick framed roofs often "settle" a little (maybe an inch or so) but when they don't have a good or robust structural strategy in place and the "settlement" becomes too pronounced, you need to install something that will provide support.

Looks like somebody started out with some sort of internal truss (not a real truss though). Maybe that's in there to create a wide opening and it looks like it is intended to support ceiling weight /loads only. Not likely to be adequate for any roof support so....laying out the existing geometry and alignment of things will be the first step.

The "L" shape of the plan and the use of hips makes it very difficult to get the framing to work well without some designated ridge support. MAYBE the ceiling and rafters are decent size so maybe there is a way to install bearing elements (walls and beams) inside the attic space.

The devil is in the details though. You really will need to find out where walls are located that are suitable for bearing. Start out with a plan drawing to see how things align (ridge lines and hip ridges at the roof and first floor walls that might be suitable for bearing, along with the size and direction of the ceiling pieces.

RE: Hip roof support

(OP)
The bottom horizontal board is a 2x6, the initial thought was to install a support from it to the ridge board at each rafter.

RE: Hip roof support

(OP)
Or would additional cross ties?

RE: Hip roof support

Putting attic walls on ceiling joists can be tricky. It really depends on how well and how closely the bearing walls on the first floor align with the new attic walls. I usually find that there are many places that require some strategy of placing walls and attic beams in order to carry the roof loading over to suitable bearing locations. I would guess that this is especially true for the L shape you describe and based on the photos.
Start with plan layout drawings for each level. Load path is the key. Bracing of attic beams is also important (remember most joists have continuous bracing but new beams in a ceiling would not necessarily have that).

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