Lean to on Shop

[knightstead]

I'm getting closed to having the inside of my shop finished and getting to the point where I need to get a plan together for my lean-to.
It'll be 44 feet long and I'd like to make it as wide as possible, hopefully 21' or 22'. The shop has a 4/12 pitch and I had the builder put
up a ledger board on the end of the trusses to make things as easy as possible. I can't continue the 4/12 pitch since the side wall will be
too low (ledger board is 13' off the ground). I was planning on a 3/12 pitch and spanning the roof with 2x10 Southern Yellow Pine rafters
(24' long) on 16" centers. End wall would be 18' from shop wall to help with strength, the other 3'-4' will be overhang. My father in law
thinks this is not suitable, and he's very knowledgeable on building, so I do value his opinion. His suggestion is to install mono truses
since they are engineered to carry the load and he believes the 2x10's will sag over time. I've priced both options and the trusses are over
$1750 and the rafters will come to roughly $1400. Has anyone spanned that far with rafters and how well has it held up? Building is an hour
southwest of St. Louis MO and we do get some snow, but typically nothing to get excited about. No building codes out there but I would like
to build this thing right the first time. Thanks for any and all input.

 

[Geo-TH,In]

Sometimes building codes are a great idea even if you live where you don't need one.
How many times do you see Bubba's metal building on the news following a tornado or straight line winds. I have to often have deal with both.

Even building to code where there is no SNOW load to worry about can lead to disaster.
Ex. My sister's neighbor has pine trees and a Florida room built to code . Pine needles covered roof. Downpour caved in roof because pine needles prevented water from flowing off roof.

I would research pole barn standards in your area.
Over building is better than seeing your twisted metal on national news.
George

 

[knightstead]

I agree with over-building and I'm willing to spend more if that's what it takes to do it right. My shop is 40x44x12.5 and is stick built, has a 3+ foot frost wall, and trusses set at 4' on center. I'd imagine it will outlast me and I'd certainly like the lean-to to do the same.

 

[Ellis Kinney]

I have done something very similar to what you are considering. You might consider 12" centers instead of 16" centers. Also, blocking will stiffen up the rafters considerably. Maybe one at 8' and one at 16'. I think 2 x 10 would be adequate. Use a board on both sides of your poles on the outside. Ellis

 

[jm.]

Big truss factory right there about an hour south of you in Mayfield ky. I would price the truss and for the $ 300 or so difference no question in my mind which way I would go. I do know a guy that has a trailer load of 2x6 yellow pine #2 they are 24ft long and if a man takes a bundle (84) he is selling them for $350.00 a bundle or just over $3.30 each.

 

[David G]

My main shop is 4/12, lean to is 2/12, both with trusses.

 

[Moonlite37]

Where do you live? I live 100 miles south of St.Louis

 

[knightstead]

I'm not opposed to using trusses but the fact that the shop is finished makes it more difficult. I'd have to install a lower ledger board over the existing sheet metal. I'm sure it can be done, just will take some time and planning on my part. I'm thinking I'd have to make a spacer of some sort behind the board so that the ribs of metal are not crushed. Then it'll take some planning to catch the 2x4 studs with anchors.

 

[David G]

My lean to is 20' wide.

 

[knightstead]

I live in St. Charles but the shop is on some family property in Crawford County. It's been in my family since 1863 and my parents and I went in together last year to build a shouse (1,000 square foot house attached to the 40x44 shop). So far it's worked out well for everyone.

 

[db4600]

Double 2x12, 8?o.c.. 16? lean.

 

[dpendzic]

assuming a snow/liveload/deadload of 30 psf, a 2x10 with a section modulus of 13.875 in cube, and a 18 ft span at 16 inches on center, the stress in the 2x10 would 1410 psi--depending on the grade of the 2x10 it may be ok--southern pine is graded by the SPIB and they have many many grades up to dense select structural which is good for 2000 psi or more
if it was graded lumber there should be a stamp on it stating the grade

 

[Janicholson]

The trusses can be engineered to be supported from the top chord. Metal brackets to the existing girt. The pine on that span will sag as flat as that is. Will you use standing seal metal roof? Jim

 

[PJH]

I would cut a strip out of the metal so the lower ledger board would lie flat against the studs.

 

[hrRoss]

i went with lam-ply 18" tall, 27ft long on my 96' shed, its the handiest machinery storage. made 2 bays 24 ft, back 15ft no-till drill in there, and 8 row planter in the other bay. rest are 16 ft for tractors haybine etc

 

[farmerjohn]

Hopefully the builder was competent in installing the ledger board securely enough to bear the weight of a roof, that?s a LOT of weight to be hanging from the end of the rafters. You say you don?t have much snow but it needs to be able to withstand the once-in-100 years record snowfall.

 

[knightstead]

The metal will have to match the existing, and it is not the standing seem. I looked into that option when we had the building put up but the expense was more than we thought it was worth. Looks like trusses are the more popular option, I'll dive deeper in that and see if I can make it work. Even if it costs more it'll save a lot of time and work cutting and adding bird's mouth notches to 34 rafters.

 

[Texasmark1]

As I remember the deflection coefficient, length dimension is linear, beam width is of the second power (squared), and height is of the 3rd power (cubed).

My shop, built with PE engineered drawings is 30x50x12, all Southern Yellow Pine, 3/12 slope, trussed, 5' centers, #3 2x4 horizontal purlins on 24" centers with a straight line roof continuation across a 15' shed using #3 2x8 rafters on the same 5' dimension. Been there since 2005 and holding up just fine. The firm was from the NE corner of Oklahoma so apparently that was the stress level for weather occurring there.

 

[Blackhole49]

The lean to on my big barn was an after thought. I tied it with lag bolts to the top of the trusses then tucked the shingles in. Mine is about a 2-12 pitch with 2x10s on 2' centers with a 13' span. I would want to go any longer than that on 2x10s. Mine was put up in 2002 in SE MI and snow has never been an issue (same with the lean to on my house which has been there 35 years). I would use the trusses. 2 of my 25 2x10s have sagged and I doubled them up. When I put the lean to on the house, it was going to be temporary so I built it with 12' 2x4s on 16" centers supported at 10'. When I decided to put a patio under it, I doubled the 2x4s. I bet neither met anybody's structural code.

 

[caterpillar guy]

30 years ago dad changed the roof slope to his garage/shop. It has 20 foot ash and oak 2x6's for rafters with just the 2x6 then 3/4 plywood for roof decking. Tar shingles and now steel over that. Steel has been on there for 10 years and rafters since the early mid 80's. No sag in that time. Central Mi, Shiawassee county. The bottom of the rafters are nailed to a stub between the plates like a pole barn then rafter nailed to them.