Since this will be a ridge BOARD vs BEAM, do i just get a 30' that's tall enough for the 2x8" rafter cut end face to full rest on the side of the ridge board? For northern Wisconsin, the live load requirement is 40 psf, but for a 10/12 pitch it goes down to 30. The local Menards uses Global LVL and their span chart is found here. The cabin will be 30' long with 4.5" wide logs, so 29' 3" inside to inside. LVL seems to be a common solution, however, i'm struggling to understand their span charts. Getting ready to start designing our tongue and groove milled log cabin and i'm trying to figure out what i'm going to do for a ridge board to make the span. Small Cabin Forum / Cabin Construction / Understanding LVL span charts for a ridge board That thing is a sail, brace it well, probably even the crown posts to ridge, hurricane ties rafters to plate, flat straps on top of the rafters over the ridge to the opposite rafter to keep it from inflating and blowing apart up top (lumber band strapping works)Īll you lack is finishing if that all works.ĭisclaimer, I'm just a nail banger, use all that at your own risk.- Forums - Register/Sign Up - Reply - Search - Statistics. The plates will have less load so should be good, the rafters already checked. Load 2375, span 120, width 3, depth 7.25, #2 syp 2x8, 10 min (wind), yes 2 members, 2&3x8, no,no, passes, the fail in deflection is for a floor, it passes for a roof at about 7/16" deflection Tributary area is 9.5' x 10', from crownpost to crownpost 2375 lbs That also works, deflection is around 13/16" Lets back up and try a 3 ply 2x12 using #1 SYP Nope but closerīump width to 6, that's a 4 ply 2x12 built up beam, Bingo, about 11/16" deflection at full load, good. Width 4.5, depth 11.25, Fb1380, the rest the same. The crown post is supporting 1/2 the 19' width side to side- 9.5' X halfway towards the front and halfway towards the rear-10' so 95 square feet x 25 lbs per square foot= 2375 lbsĮnter load 2375, span 240, width 4, depth 10, Fb 1536, E 1.4, Fv 280 The middle bent is bearing the most load so we'll check it. Span 10'x2' on center x 25psf=500lbs per rafter Side girders, uniformly loaded, same calc as just above. The ridge should be an LVL, the supplier will spec it for you, prolly a triple 14" (if you want to play with it lvl Fb 2800 psi, E 2.0, Fv 280) 3 full dimension 2x12's in #1 passes, 1-1/4" deflection at full load, it's probably not going to feel real good walking on the roof at midspan. Not even close, deflection 13", its headin for the ground. It is uniformly loaded, calc here ĩ.5' of tributary width x 24' long x 25 psf=5700 lbs load. try 3 full cut 2"x10'sįb goes to 1619 the rest are the same, passes barely in bending, deflection at full load is 1". If built VERY light call the dead load 5psf so 25psf x 114sf=2850 lbsĪdjusted for wind, Fb for SYP is 1536 psi, E is 1.4, Fv is 280psiĮnter all that into the calc, nope. Code minimum live load is 20 lbs per square foot. The post is supporting half the ridge so 12'. The ridge is supporting half of each rafter pair so 9.5' of width. I'm assuming we're talking about southern yellow pine. Ply and osb don't really make a beam stronger, they might add a tad of stiffness but I just neglect them in any strength calcs. The other guys type faster, and we got a storm blackout blip partway through my post dang it.Ĭedar isn't beam material.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |