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roof structural advice please

roof structural advice please

roof structural advice please

(OP)
house built 1952. A few rafters cracked and one is split. Im considering adding supports. Advice?

tks,
pa

RE: roof structural advice please

(OP)
more pics coming.

RE: roof structural advice please

If you add a 2x4 brace down to the top plate of the interior partition wall, that won't do any good if the wall was originally non-bearing, and has only 1-2x4 top plate and studs at 24" o.c.

Better to sister those rafters.

RE: roof structural advice please

(OP)
two 4 feet long 2x6, both sides of damage, liquid nails and structural screws?

RE: roof structural advice please

or do it properly and put a new full length rafter. Then you don't have to worry about it cracking/splitting in a separate location.

RE: roof structural advice please

One full length like jayrod says.

RE: roof structural advice please

What is the white stuff all over the rafters? Glue?

RE: roof structural advice please

I had the same question,

I assumed they had roof leak issues and figured if they siliconed all of the possible areas of water penetration it would help. It to me just looks like a messy, futile effort.

RE: roof structural advice please

(OP)
white stuff subfloor adhesive. qualified sources instruct to use subfloor adhesive rated apa-afg-01 to adhere roofing planks and gable support members for added strength during a hurricane. Insurance companies give discounts for such after inspection. While I was doing such a few years ago, I noticed that split, so i squired some in.

RE: roof structural advice please

ahh I see. I live in NEPA so I've never seen anything like it.

RE: roof structural advice please

I live in Florida and have done a lot of roof and attic inspections, including filling out an insurance discount form, and I have never heard of applying adhesive of any type like that to help for uplift. I think it was a waste of time, sorry, I do appreciate your efforts. Unless you apply adhesive before joining together two wood members, applying it along the joints or edges isn't likely to do much of anything. On the subject, there is currently research on the usage of spray-on adhesive polyurethane foam (similar to Great Stuff - yellow foam in a can) along the truss-roof deck joints in order to improve uplift resistance, but that is a different beast than subflooring adhesive.

The big thing in uplift is roof rafter anchorage to the walls via uplift connections, and gable end bracing. The former is nearly impossible without removing soffit and other stuff at a minimum because access is nearly impossible. The latter is fairly simple and I recommend doing it, you have the space and clearly have an unbraced gable end, and it usually is one of the things that insurance companies offer discounts.


Here is a good website on the subject. Scroll down to the end of the document for the details on gable end bracing.

http://www.floridadisaster.org/hrg/content/roofs/b...



The other thing you could do for uplift improvement is to reinforce where the rafters connect to the ridge beam, looks like it is just toe nailed. You want to prevent the rafters from failing via uplift by shearing out those toe nailed connections (low capacity).

You could go a couple of different routes:
http://www.strongtie.com/ftp/fliers/F-LRU12.pdf
Or some type of twist strap that would connect to the sides of both rafter beams and go under the ridge beam.

RE: roof structural advice please

(OP)
sites referenced list using the subfloor adhesive and/or that spray-on adhesive polyurethane foam for uplift. Sites u referenced I been and got some of my info. I have not talked about the hurricane straps that i have added or the gable end supports that I have planned, because they are not relevant. Soffit removal and replacement was easy. Needed to add extra screws anyway. I decided to replace roof and decided to fix these cracks 1st. Then finish do rafter tie downs and gable bracing after the new roof. 4/12 roof gables are not as prone to failure as steeper roofs. When the old roof material is removed, i will use grk R4 - #10 x 3 1/8" screws to secure the planks and especially at the gable and soffit ends. this is one of the suggestions to help support gables. Actually 9D shanked nails are recommended. Once screwed down, i wont need the subfloor adhesive or foam for plank uplift.

Im not looking for info on how good or smart it was for me to just shoot some subfloor in there w/o really thinking. If I thought it was adequate, I would not be here.

rafter to ridge beam will be with right angle simpson A33. However, since none of the sites suggest this, its one of the last things i will do.

Also adding vertical supports between rafters and joists. However all this is not why Im here.

RE: roof structural advice please

(OP)
Im not even sure I posted the right pics, since i cant see them on this site without downloading them. too much trouble to post and download pics here.

RE: roof structural advice please

paulmars, consider reviewing the screws shear value. Some screws are not appropriate for the shear wild loads.

RE: roof structural advice please

(OP)
no way to get a full length 2x6 up there.

What are the best strongest screws to use?

RE: roof structural advice please

Boy, from the first few photos I was wondering if the house was just glued together!

Mike McCann
MMC Engineering

RE: roof structural advice please

I have personally used the Simpson SDS. Excellent.

RE: roof structural advice please

I agree with AELLC. The simpson fasteners are outstanding. The GRK brand is good as well. Standard wood construction screws don't match up.

On the topic of a full length 2x6, remove a piece of the soffit and slide it up from the outside, it's quick and easy as long as you pay attention when taking the soffit down

RE: roof structural advice please

(OP)
tks. Ive considered that "On the topic of a full length 2x6, remove a piece of the soffit and slide it up from the outside, it's quick and easy as long as you pay attention when taking the soffit down", however Id need to remove fascia too and drip edge. Its just too involved. Neither of these are sagging, but still Id like to strengthen.

which screws stronger grk or simpson. I need 1" and 3"?

RE: roof structural advice please

Can't tell you off the top of my head. you could just go to each website and compare.

RE: roof structural advice please

(OP)
Ive tried that "you could just go to each website and compare." GRK does not spec their #10 RSS, just their 1/4" and larger. I dont want to use that large a screw. Additionally, Im not sure the specs are directly comparable.

Im actually considering using both, but that sounds lame. Like the guy down the street when I was a kid who used 1 quart each of 5 different brands of motor oil when he changed his oil.

p

RE: roof structural advice please

The Simpson SDS comes in only 1/4" diameter, 1.5 to 8 inches long.

The SD is only 8 ga x 1.25", but Simpson says the SD is not structural - but try telling that to me, the SD is far better than using a nail. BTDT.

ROTFL @ 5 different brands of oil. I hope he didn't use Pennsylvania-origin oil.

RE: roof structural advice please

(OP)
Thank you

 

RE: roof structural advice please

I have additional info on Simpson SD9, etc fasteners, and long screws that replace H2.5 type ties, etc.

The SD9's are structural and they look to be more appropriate than the SDS types and the SD8, which is non-structural. They are an allowable substitute for nails in Simpson hardware and they may increase the actual capacity significantly by preventing nail withdrawal. (even double the actual tested load capacity)

RE: roof structural advice please

I thought SD's were only for metal connectors. SDW screws are specifically rated to sister PSL, LVL members together. SDS screws would also work well however, would go at least 3/4 full length as long as bearing ends look okay,...shear won't govern. If framing members are 2x6's you probably will not have an issue with the not having enough surface contact for double row stitch screwing as you would if you had the typical 10 to 12 foot true cut 2x4 Berkeley span members with 3 inches of deflection center span. Just do your shear flow calc on the fastener spacing,....closer at ends, further in the middle. You can Google the shear flow equation/calc for fasteners,...no kidding. Good luck.

RE: roof structural advice please

PS. Regardless of the screw you decide to use, should work base upon proper allowable shear load capacity with correct shear flow calculation. Also, screws must be full depth,....e.g. 2-2x members = 3",....use 3" long screw, not 2 1/2" long. think SD screws max out at 2 1/2" so that would throw them out of the running,.... but you should check to make sure.

RE: roof structural advice please

The SDS are too large for most Simpson connectors. That is what I meant. To use screws instead of nails in H2.5's etc to increase capacity dramatically.

At the Simpson seminar, they load tested sawn lumber fastened by a single H2.5A, using nails. Failure at 3500#. Failure mode was nails bending and pulling out. The H2.5 was mangled but in one piece.


Same thing with SD9's. 8000#, failure mode was the H2.5 snapped apart suddenly. The connection to the wood itself was tight.

RE: roof structural advice please

(OP)
Whats the best grade bolts to use for two 4' sisters, one each side of the 1st crack (wood knot)? I think four bolts would be good. Washers too.

RE: roof structural advice please

I prefer screws over bolts, always have. The Simpson screws are very pricey but superior. Look at their SDW series.

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