LumberJocks

New Shop - from the ground , up. #2: Help! Laminated Veneer or dimension lumber build up?

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Blog entry by curliejones posted 11-24-2013 01:58 PM 1135 reads 0 times favorited 5 comments Add to Favorites Watch
« Part 1: Site work - not exactly FINE woodworking. Part 2 of New Shop - from the ground , up. series Part 3: Finally - something I can see! »

Here’s a sketch of the shop I hope to start soon. I’m pretty good with framing and have used post and beam for sheds and stick framing in the house. I am at a sticking point in design over something I’ve not used before, LVL (aka microlam). The sketch shows the front of my proposed shop as 22 ft across and shows a simple shed roof at a 2/12 pitch. I’m in SE Louisiana and have short duration snow loads, though rarely even that. Halfway across the 22 ft and at rafter level you see an X marking the spot for a beam that runs the length of the shop, 30 ft. You are looking at the end of the beam. I plan to put a post, built up from dimension lumber at the halfway point, or 15 ft. I’ve been searching the tables and having a tough time with them for sizing the beam. The requirements as I see them: I want a beam that can span 15 ft and another beam end to end that can span the next 15 ft to cover the distance front to rear of the shop. I know there will be some days when I’ll wish the was no post in the middle of the shop, but I also see it as a way to have a drop point for dust collection and electricity, avoiding cords and hoses running to walls. I can live with it. I’ve called a couple of local lumber yards and they (liability) want me to spec the size. Seems most advice says go to a “real” lumber yard and they will call the manufacturer who will help you size it. Let’s say response has been slow so far, but I still have some diminishing hope. – What’s on top? I want the beam to support the rafters directly; I will not use ceiling joists. The rafters will be 2X8s 12 ft long, 24” oc, overlapped by a foot each and nailed together atop the beam. I want to sheath the roof with plywood, probably 5/8” sheathing grade. I will use tar paper and then a bubble foil, strip every three ft with 2×4s and fasten a 26 ga. metal roof – not a really light or really heavy roof load unless…. – A few years ago we had an eight inch snowfall here, extremely rare, and my home made house and sheds came through that just fine. I need to be able to “weather” that event should it occur again. I’m 62 and it was the greatest snowfall I’ve seen. WE have had sustained winds in excess of 100 mph (Katrina) and The 2×6 walls will be completely sheathed with plywood for shear strength. – So – in my amateurish estimation, there’s a deadload of 15 psf and a live load of short duration, possible of 20 psf? That would be the rare snowfall. If I correctly appreciate the physics involved, the roof loads are supported on one end by the the 2×6 walls with double top plates and shared on the other end by the beam they rest upon. – Thanks to the curious who have hung in with me thus far. The “Calling all LJs” part of this is has anyone built such a beam to span 15 ft using (3) 2×12s? My case would involve (6) 2×12 as I place a second beam end to end and I’ve considered a slight stagger of the middle 2×12 by about 1.5 inches to created a tongue and groove effect for the end to end joint where the beams meet. I would join the beams additionally with scabs or metal plates. – I know LVL is in style these days, but I’d like to know my options. Getting some SYP 2×12 is easy work, but ordering the LVL is getting to be a pain. I’ve seen the rules of thumb for LVLs such as 1” of depth for each foot of span. My unsupported spans end up being close to 14 ft with the required bearing surface on each end, so I’m thinking two 1-3/4” X 14” AND 15 FT LONG lvls nailed together would make one beam, then do it again and place it end to end. My goal here is no sagging no regrets! – Thanks so much for sharing your experience with 3 2×12s and or lvl doubled up.

-- Like Guy Clark sez - "Sometimes I use my head, Sometimes I get a bigger hammer"



5 comments so far

View cabmaker's profile

cabmaker

1311 posts in 1560 days


#1 posted 11-24-2013 02:33 PM

15 ft? Double 2×12 should be no problem!

Why not rafter the 22ft run and eliminate any or all interior supports ?

If your wanting the exposed beam look on your elevation just put in a dummy.

Jb

View Bigrock's profile

Bigrock

253 posts in 1714 days


#2 posted 11-24-2013 02:40 PM

Hi:
I was wondering why 22’? Most materials come in 4. Is it a lot problem? If it were me and the little cost I would make it a min. of 24’. You will be surprise how fast you will fill up a shop with tools and other items.

You may want to look at a steel beam which would not be as tall or a wood box truss. You do have choices out there today. Look at all of them. Talk to a local Structure Engineer. I have a 28’ x 28’ shop with 10’ ceiling without any columns to get in the way. I used trusses (6 to 12 pitch) loaded for storage and fold up steps. Wood storage.
Have Fun

View nailbanger2's profile

nailbanger2

969 posts in 1895 days


#3 posted 11-24-2013 04:20 PM

Another fan of trusses here. If you go with SYP rafters, they should be 16” O.C.

-- Wish I were Norm's Nephew

View curliejones's profile

curliejones

88 posts in 1018 days


#4 posted 11-24-2013 04:24 PM

Hi cabmaker and Bigrock. —I believe the 22ft run would take 2×10s min spaced 16”oc. I was going for the lighter stuff for ease of handling, usually working alone.
Same reasons for a steel beam, tuff for a DIYer working alone. Trusses, same issue. Getting outside help to come when I need them??? well I guess I have trust issues other than in myself.

-- Like Guy Clark sez - "Sometimes I use my head, Sometimes I get a bigger hammer"

View curliejones's profile

curliejones

88 posts in 1018 days


#5 posted 12-15-2014 12:01 PM

Footnote* I’m reviewing my chronicle since the shop is finished. I consulted a vendor who put me in touch with a manufacturer of glu-lam beams. A 3.5” x 12” was all I needed and enabled me to use 2×8 rafters, easily handle by one (me) climbing a ladder. I supported the beam in the very middle of the 30 ft span with a built-up post made of (6) 2×4s and (2) 2X10s with the beam resting atop the 2×4s and between the 2×10s making a saddle for the beam ( see pics in Part IV of this series). I decided on a 26 ft span minus the 2×6 walls and the clear span ended up at 24-1/2 ft. The one post in the very middle of the shop give me a spot drop electricity and eventually dust hose and perhaps air, if deemed necessary.

-- Like Guy Clark sez - "Sometimes I use my head, Sometimes I get a bigger hammer"

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