snow and tile load on roof
My log home engineer came down with Alzhiemers 6 mo. after clearing my roof system for 150 lbs/sq ft; combo of concrete tile and snow load. <!—-><!—-> <!—->
I have a ridge beam and purlons 16″-18″ diam. of doug fir, 14/12 roof pitch, with a span of 14 ft between the ridge beam and purlon, the span is sheathed with 2×6 T&G doug fir decking running vertically to the beams, insulating panals (7 1/2 foam with one face of 1/2 OSB) that are glued and screwed to the decking.
I’m having second thoughts about my engineer because when I walk and bounce on the roof I get some flex (less than 1/4 inch). Should I be concerned and if so how do I fix it? I do have the clearance in writing.
Call another engineer.
Birth, school, work, death.....................
Please call another engineer. Not to insult your previous engineer, but you can't be sure how many episodes were chalked up to lack of sleep or senior moments before being diagnosed.
...that's not a mistake, it's rustic
Sounds like the engineering should be double checked.
The ridge beams and purlins in the attached image are 14" to 15" average diameter (logs: 10" tips, 16" to 18" butts). I don't have the numbers in front of me but I believe the spacing between purlins along the trusses (there's another truss not seen in the photo to the extreme right) was 8'. The span between trusses was about 28'. The loads on the roof were similar to yours.
There was NO "bounce" in these ridge beams and purlins whatsoever. (I know all beams deflect ... there just wasn't enough in these members that a person could sense it).
Edited 11/18/2005 10:57 am ET by JoeBartok
You should have it double checked.
My guess is that the 14' span of 2x6 t&G decking is where the deflection is comming from, but can't tell for sure.
You are correct, the flex is in the decking. Site inspection is difficult because of location. The T&G is the ceiling on the inside. I need to "fix" from the outside.
Edited 11/18/2005 2:33 pm ET by chauncey
I, unfortunately, am not that familiar w/ log home const. I simply suspected that 14' seemed like a long span for 2x decking laying flat.
The only guess I have, for a fix, is to somehow "channel" out the foam core at the joints of the roof panels (running the 14' lenght) and insert 2x6's "rafters" on egde in the channels. Although only occuring at +/- 48" oc, this would increase the deflection rating somewhat.
I have NO idea if this would work, but your choices appear to be quite limited.
PLease check w/ a local engineer, preferable one familiar w/ log homes.
I'm not an engineer but that 14' seems a bit long to me; almost double the 8' in the example I posted. And how long is the span between the purlin endpoints?
Edited 11/18/2005 4:42 pm ET by JoeBartok
The "channaling" idea is workable because that turns the roof into a large hollow core door. But at this stage it would be a real pain in the ---