Wood shed roof strength

[Dudders]

Is it a lean-to against a taller building? If so, you could support the central section with chains from a higher point, or several points. It's what I'll be doing for a lumber shelter very soon, albeit not as deep as yours, but it'll be 45' long in one span. The other building has to have the strength to take it, which mine does. Otherwise, I'd strategically position a hefty power pole or two and run chains (or cables, as holeycow says) to take the weight. Turnbuckles to adjust perfectly.

 

[Yarz]

Do you need the clear span for the entire height of the opening?
If not, you could add 45° braces in the upper corners, reducing the distance without support. Then if you're putting your wood in with something like a skidsteer/tractor, you can lower the wood to drive in (full width is available), then lift up to stack as needed.

Something like this:
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[Dudders]

I put this barn up about 40 years ago, but had to replace the roof and all its timbers 15 years ago. The first roof I put on was single-skin plastic, and condensation was forever dripping off it onto hay and straw stacks, eventually rotting all the timbers as well. So it all came off and I remade it with 2" insulated roofing sheets on a framework of second-hand softwood timbers. The spans are 15' between post centres, 3 bays. The front beam is 3"x 8", the others 2"x 9". There's never a heavy snow-load, although the roof has a shallow pitch. As you can see, it's all still dead straight. I reckon the same dimension timber could take another 5', if the roof was steeper and you put in Yarz's braces at each end. But I'm not an engineer - I just go by what feels right!

All the lumber came out of a demolished large Victorian house, dating from about 1850. I don't know what it is, but it's beautiful stuff, good as new, must have come over from North America in one of the tall ships, maybe a clipper like Flying Cloud? Growing to a great size, felled and milled, shipped over the Atlantic and then 150 years of history in the roof of a family house - 2 world wars, etc - before re-use here. And this barn might not be the end of the story - the timbers could still be around doing another job in 200 years' time. Awesome.

The back of this barn is where the lean-to lumber shelter will go - one clear span from end to end, 45' in all. As the new roof will be lower than the main building, chains will support it from the higher building.

 

[Oldtoolsnewproblems]

45 braces in corners are definitely happening, also I found my strength tables and I'll be following up with both what the right thing to do is, as well as what I actually end out doing

 

[esshup]

Ok honestly I had thought a lot about a removable post and I think I'll go back to just doing that, keep it simple etc.

The only thing that comes to mind with a removable post is with the snow load. If the load deflects the beam enough, removing the post will be a PITA as well as getting it back in. You might need a hydraulic jack to take enough of the deflection out of the beam to get the post in and out, then you have to watch to make sure the beam doesn't crack with the snow load.

Another way to eliminate that problem is with a snow rake and clean off the roof before removing the post.

 

[Marine5068]

Hopefully this is the right forum.
Title hopefully says it all. I'm building two lean-tos for drying wood. One for firewood and one for drying lumber. The one for lumber is gonna be 7ft by 18 or 20ft. Steep slope to shed snow since I'm in new England and we get a fair bit. I know I'll be to put some anchors in the ground to deal with wind loads, even though it's in fairly shaded woods so it won't get nailed.
My big issue is I want to minimize the number of posts to make getting long lengths in and out easier. Was hoping to get away with only one in each corner in the open side, but I could be convinced to add one 5ft from one end for extra support.

Normal roof guidelines are not very helpful when you're only spanning 7ft, way less load than usual. Was hoping to get away with sistering a 2x4 to a 2x6 because that's what I have left in my scrap pile. Just looking at it it almost feels like a 4x4 would even be enough, but I could be wildly wrong

7' span would require a 2x6 at least.
Why not use 4"x4" post anchors, the kind you hammer in?

 

[Marine5068]

I put this barn up about 40 years ago, but had to replace the roof and all its timbers 15 years ago. The first roof I put on was single-skin plastic, and condensation was forever dripping off it onto hay and straw stacks, eventually rotting all the timbers as well. So it all came off and I remade it with 2" insulated roofing sheets on a framework of second-hand softwood timbers. The spans are 15' between post centres, 3 bays. The front beam is 3"x 8", the others 2"x 9". There's never a heavy snow-load, although the roof has a shallow pitch. As you can see, it's all still dead straight. I reckon the same dimension timber could take another 5', if the roof was steeper and you put in Yarz's braces at each end. But I'm not an engineer - I just go by what feels right!

All the lumber came out of a demolished large Victorian house, dating from about 1850. I don't know what it is, but it's beautiful stuff, good as new, must have come over from North America in one of the tall ships, maybe a clipper like Flying Cloud? Growing to a great size, felled and milled, shipped over the Atlantic and then 150 years of history in the roof of a family house - 2 world wars, etc - before re-use here. And this barn might not be the end of the story - the timbers could still be around doing another job in 200 years' time. Awesome.

The back of this barn is where the lean-to lumber shelter will go - one clear span from end to end, 45' in all. As the new roof will be lower than the main building, chains will support it from the higher building.

That's great but not here in Ontario, Canada. We can get 3' of snow up on a roof and then a huge wet rain after. Ours needs to be heavy engineered roof support here. Basically just means it costs more money to build here.

 

[holeycow]

And here in northern Alberta my calf shelter wood storage has the opening door mid-span header support removed and has a clear-span length of about 15 1/2 feet. This with a single planed 2x10 fir header board. There's only a tiny deflection after about 10 years of being this way (centre post removed). If the snow builds up I can shovel it off in 10 minutes (which I've never had to do).

dry snow, dry cold. I couldn't do this in many areas.

 

[Marine5068]

2"x6" Eastern White Pine rafters at 18" o/c over 9'10" span with H 2.5 hurricane ties. 1 centered row of 2x6 blocking and 1x4 strapping every 12" with metal roofing.

 

[Oldtoolsnewproblems]

ok most load refs that are for sawn lumber and not lvl max out at 14 ft span, which I can live with by making the mfrom angled brackets up high in the front, and on off center post to give a 14ft max span. assuming i cut down my panels to 7ft and give it a 6in/ft slope, i end out with a 6'3" roof area and an aggresive 27 degree roof angle to help shed snow weight. using absolute worst snow loading for my area of 50psf, which is unreasonably high, I can get away with a 4x8 beam or two 2x10s sistered, and honestly a 2x8 sandwich is close enought to meeting spec that I could get away with it.

for fun I'll re-check the nubmers for a true 20ft span and see what it comes to. would ppl be interested if i figured out how to share the worksheet i made?

 

[holeycow]

You could incorporate plywood into your built-up beam also. Nailing pattern is important! And use glue, like pl400, 500 or similar. Ideally, use long enough nails so they can be clinched (across the grain). Overkill, but strong.

 

[Snap]

Hopefully this is the right forum.
Title hopefully says it all. I'm building two lean-tos for drying wood. One for firewood and one for drying lumber. The one for lumber is gonna be 7ft by 18 or 20ft. Steep slope to shed snow since I'm in new England and we get a fair bit. I know I'll be to put some anchors in the ground to deal with wind loads, even though it's in fairly shaded woods so it won't get nailed.
My big issue is I want to minimize the number of posts to make getting long lengths in and out easier. Was hoping to get away with only one in each corner in the open side, but I could be convinced to add one 5ft from one end for extra support.

Normal roof guidelines are not very helpful when you're only spanning 7ft, way less load than usual. Was hoping to get away with sistering a 2x4 to a 2x6 because that's what I have left in my scrap pile. Just looking at it it almost feels like a 4x4 would even be enough, but I could be wildly wrong

Snow load specs vary by town in my new England state and there are many zones in the state to the north. It used to be a simple starting point but it's an exercise now just to get to the starting point. A 2x4 has very little load carrying capacity (a 4x4 twice very little) and a few years ago I saw over four feet of snow on a lot of roofs south of Boston. Figuring 30 pcf and that's more than a gym floor load.
Your state may or may not have requirements for such a structure but if not then you'd have to decide how important not collapsing is to you. Actually though, lumber for a substantial beam isn't a big investment for piece of mind.

 

[Snap]

I see mention of LVL......they are not good for possible wetted use. Think what happens to plywood left exposed.

 

[Snap]

45 braces in corners are definitely happening, also I found my strength tables and I'll be following up with both what the right thing to do is, as well as what I actually end out doing

Those braces are not going to reduce your span. You are not going to make adequate connections to make the braces work in that manner and even if you did it would put significant bending in the posts that they connect to so they would need quite a bit of beefing up; robbing Peter to pay Paul.
I always laugh at toe nailed knee braces. Might as well have saved the lumber and not have done it at all because it's just window dressing.

You should design your beam for the full span between posts and use the knee braces to provide lateral stability.

 

[Snap]

ok most load refs that are for sawn lumber and not lvl max out at 14 ft span, which I can live with by making the mfrom angled brackets up high in the front, and on off center post to give a 14ft max span. assuming i cut down my panels to 7ft and give it a 6in/ft slope, i end out with a 6'3" roof area and an aggresive 27 degree roof angle to help shed snow weight. using absolute worst snow loading for my area of 50psf, which is unreasonably high, I can get away with a 4x8 beam or two 2x10s sistered, and honestly a 2x8 sandwich is close enought to meeting spec that I could get away with it.

for fun I'll re-check the nubmers for a true 20ft span and see what it comes to. would ppl be interested if i figured out how to share the worksheet i made?

You are at a bit of a disadvantage trying to use load tables. Running the actual calculations removes span restrictions that you're finding.
Anything is possible if you commit to pay for it.
If convention wood framing isn't making it for your hopeful span, finding a source for used steel would be a clear span solution.

 

[Marine5068]

This is the woodshed I built (overbuilt) last year. It is 12' x 30'. I used 16' 6x6 posts, triple 2x10 beams, and 16' 2x8" rafters on 2' centres. The wood piles are over 7' tall. The roof is 4/12 pitch and the snow comes off the steel roof real easy, never any sag in the roof. Material cost was under $4,000.

Here's mine I just finished.
26'x10'x8'tall
2x10 beams, 2x6 rafters, P.T. decking for siding with air gaps, P.T. deck in firewood section, gravel floor in wood splitter storage section.
Metal roof
Just needs the doors built now.

 

[Snap]

Here's mine I just finished.
26'x10'x8'tall
2x10 beams, 2x6 rafters, P.T. decking for siding with air gaps, P.T. deck in firewood section, gravel floor in wood splitter storage section.
Metal roof
Just needs the doors built now.

View attachment 964170 View attachment 964171

Looks nice but I'd do a little figuring on the nails transferring the beam loads to the posts (unless I am not seeing the whole picture).
I usually see nail capacities listed for less than 100 pounds each depending on the wood species/grade, nail size and penetration.
Maybe a stud or cleat under the beams at each post would be inexpensive insurance.

 

[Marine5068]

Looks nice but I'd do a little figuring on the nails transferring the beam loads to the posts (unless I am not seeing the whole picture).
I usually see nail capacities listed for less than 100 pounds each depending on the wood species/grade, nail size and penetration.
Maybe a stud or cleat under the beams at each post would be inexpensive insurance.

Yep.
Front beams rest on top of the front posts attached down with hangers and face supported with diagonal braces.
They kind of look like nails but you can see the 4 structural screws at each post, made for post and beam fastening.
But I was thinking of adding a 2x block under each beam inside and against the post with a couple more structural screws in the blocks for added shear strength.
Won't hurt.

 

[Marine5068]

So the plan is to use 8ft roof panels at a step enough slope to shed snow, so it will probably be 6-7 feet deep, then maximum possible open front span to make it easy to bring in some long lumber I cut. Figure less than 20, more than 15 would be ideal. I know it will be a pretty large beam but I'd rather not manhandle large boards thru a small opening.

This is for drying lumber, not firewood. Also some tool storage

Why not bring the lumber in the end. That way you can locate the posts closer and reduce the beam size.
Plus your 20' beam span will be hard to find. Not much 20' lumber out there.
You'd have to mill one or have it milled or buy a laminated beam to get that length(20') and depth(18")

 

[Oldtoolsnewproblems]

sorry got locked out for a bit and felt lazy. I ended out felling a dead standing tree that was right next to where I was setting up, and it was exactly the right diameter,, didnt mill it or anything, just put a mortise at both end , added legs and tilted it up. was feeling real proud of myself until i was nocking the bark off getting ready to put a lid on it when i saw the crack it took when it fell..... curse words.