Lean-to shed

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tmccar
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Lean-to shed

Post by tmccar » Tue Jul 09, 2019 4:39 pm

I am looking for soem advice on building a lean-to shed between 2 existing buildings, using 4x2 joists. I would like to build it against the tall shed on the left of the picture.
I was wondering how to tie it to the wall, and how to proceed with the wall framing?

Also, how best to seal the roof at the join? (I will probably have a shingle roof)
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A. Spruce
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Re: Lean-to shed

Post by A. Spruce » Tue Jul 09, 2019 6:31 pm

I think I would extend the roof of the left side building. You will need a headers between the buildings along the front and back. If you attach to the buildings, you can anchor into them, otherwise you will have to install footings and posts to support the headers. With the headers in place, lay your rafters, then sheet over those, and finally install the roofing. It's just that simple.

The hard part is figuring out the correct height of the headers so that your roof deck is the same plane as the existing roof deck to tie the roofs together seamlessly. I say "hard", but it's not all that difficult, and you can lay it all out to scale to figure out what the total height of the header/rafter/sheathing is going to be, and this will tell you where the header will be placed against the building.
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Shannon
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Re: Lean-to shed

Post by Shannon » Wed Jul 10, 2019 7:20 am

If those buildings are the same height I would look at actually spanning the distance with roof joists and simply over lapping the new roof onto the side buildings around 12" or so. even if one is lower then the other I still would do that and just build up the lower one.
Is this a possibility for you?
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tmccar
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Re: Lean-to shed

Post by tmccar » Thu Jul 11, 2019 5:20 pm

Sorry, I've been away for a while.
That's interesting - I had not considered spanning the distance between the sheds.
I'm not sure if it would be practical - the one on the right is a couple of feet lower than the other one.
But I suppose I could build up the lower one as you suggested.
Both roofs have corrugated iron sheets.

What about the side walls - should I frame these as per a standalone shed?

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Re: Lean-to shed

Post by A. Spruce » Thu Jul 11, 2019 5:53 pm

If the existing sheds are structurally sound, I'd simply attach the headers to them. On the shorter shed side you may need to build your own supports, just depends on what you have to work with.
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Re: Lean-to shed

Post by Shannon » Thu Jul 11, 2019 10:01 pm

The problem I see with attaching to the side of sheds you will never get that seal sealed well, you will have leaks. If you lap over the other two, in my mind you eliminate that.
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Re: Lean-to shed

Post by A. Spruce » Thu Jul 11, 2019 10:40 pm

Shannon wrote:
Thu Jul 11, 2019 10:01 pm
The problem I see with attaching to the side of sheds you will never get that seal sealed well, you will have leaks. If you lap over the other two, in my mind you eliminate that.
Working from the higher side, in essence, the roof is simply being extended. When tied in properly, there's no reason that there should be a leak there. IMHO, you have more chances for leaks with an elevation change than simply extending out the roof line.

On the low side, there won't be any choice but to have some sort of wall between the higher roof line and the lower roof line, and this could be a leak point, so there will have to be careful attention to how it is built and flashed so as to keep the water where it belongs. I'm not familiar enough with metal roof to know what kinds of flashings are available for such a transition. I believe the OP said it was corrugated roof panels, which means flashing could be difficult on a transition wall.
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Re: Lean-to shed

Post by Shannon » Fri Jul 12, 2019 6:46 am

yes you would have to do a flashing for sure to tie new roof into old roofs. This may require a custom bent flashing depending how you set things up.I was thinking in my mind of a simple roof butted to that wall and there was no way that was not going to be a problem over time. Brain fart on the flashing on my part
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Re: Lean-to shed

Post by tmccar » Sat Jul 13, 2019 5:15 am

Ok, so the header - I'm guessing that this will need to be substantial (say 6x3) and will be bolted to the existing left and right walls, and runs the length of the new shed??

I think I will have a go at extending the roof as above. I will try to get more photos which may help to throw some light on it.

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Re: Lean-to shed

Post by Shannon » Sat Jul 13, 2019 8:38 am

How much distance between those buildings? Do you have a snow load in your area to factor in? Are you building a foundation? Is this built on the ground or is this a roof top on a flat roof building?
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Re: Lean-to shed

Post by tmccar » Sun Jul 14, 2019 5:49 pm

There's about 13' between the sheds, and there's no snow load to worry about.
I'm not building a foundation - I have a bed of gravel over an old concrete floor (I was thinking of laying 3 skids on this)
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Re: Lean-to shed

Post by Shannon » Mon Jul 15, 2019 8:19 am

I would likey use a 2 ply 2x10 myself.
Let’s see what Spruce thinks?
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Re: Lean-to shed

Post by A. Spruce » Mon Jul 15, 2019 10:56 am

I'd install a ledger along the high side roof line so that the new finished roof will plane in exactly with the existing roof. On the low side, I'd unscrew the roof over the top of the wall, bend it upward, then extend the wall up so that the rafters spanning the gap will sit on the wall and be level.

I don't have a span chart handy, a 2x10 sounds about right for a 13' span though. The rafters would be installed with joist hangers on the ledger and toe nailed into top of wall on short side. I'd also cap the end of the rafters with a 2x10 to keep them stable and give you something to attach siding or roofing to for the transition between the high roof and the low roof.
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Re: Lean-to shed

Post by tmccar » Mon Jul 15, 2019 11:02 am

So ledger will go approximately here?
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A. Spruce
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Re: Lean-to shed

Post by A. Spruce » Mon Jul 15, 2019 11:12 am

roof1.png
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Here's a quick drawing for you. The black portions are the existing buildings and roof.
1 - The light blue is the 2x10 ledger on the high side, the gray is the rafter, the red is the end cap I was describing.
2 - The green is the wall extension to support the rafters.
3 - The dark blue is the existing roofing. You will overlap the new roof (purple) over the old on the high side. On the low side, the roof will either end with an overhang or cascade down the end of the rafters and overlap the vertically bent piece of the old roofing. The vertical face of the new roof can be roofing or siding, but whatever you put here, it must overlap the low side roof so as to have a water tight connection.
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tmccar
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Re: Lean-to shed

Post by tmccar » Mon Jul 15, 2019 3:00 pm

Ok, I see, thanks.
There's a bit of work in that.

-What roofing material would you use?
And what about the ends - a regular timber frame wall?

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Re: Lean-to shed

Post by A. Spruce » Mon Jul 15, 2019 3:28 pm

I'd used corrugated metal, it's what's there, the new should match up to the old well enough

Ends of what between the buildings?
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Re: Lean-to shed

Post by tmccar » Tue Jul 16, 2019 2:38 am

I mean, how to close the ends. I now have just a roof and 2 existing walls.

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Re: Lean-to shed

Post by A. Spruce » Tue Jul 16, 2019 9:28 am

If you take the handrail down, you can fill the block wall and attach a sill plate there for a back wall. The front can be framed any way you like, I'd probably be inclined to install a roll up garage door, which will close on gravel just fine. If you want to frame it down and have a normal passage door, then you're going to need to pour a footing for the front wall to sit on. It doesn't have to be extravagant, maybe 6" square, you just need a flat surface to support the wall securely.
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Re: Lean-to shed

Post by tmccar » Wed Jul 17, 2019 11:54 am

Ok, and for flooring - would 3 skids supporting a frame of 4x2's be ok?
And -any advice for sealing between the back and side walls?

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Re: Lean-to shed

Post by A. Spruce » Wed Jul 17, 2019 12:37 pm

I would recommend leaving the floor gravel or pouring concrete. If you do a raised floor, you're inviting rodents and other critters and pests to come make a home, and the last thing you want is something dying under there.

If you pour concrete, then your front and back walls can rest on that just fine. As for sealing the new walls to the old, those old walls are in pretty rough shape, literally and figuratively. I would probably use T1-11 siding for now, caulk the joint and cover with trim, and plan of putting on stucco later (do it now if you can afford it or do it yourself). Stucco is going to be a similar finish to both of the existing structures, and IMHO, the name of the game when doing remodel work is that it blends in as if it's always been there, and this shed is no different. You want to add value to your property, not create blight.
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tmccar
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Re: Lean-to shed

Post by tmccar » Sat Jul 20, 2019 5:02 pm

Ok, thanks for the advice!

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Re: Lean-to shed

Post by tmccar » Tue Jul 23, 2019 5:20 am

I would like to keep my roof at the level of the lower shed (mainly because the taller one is much taller than I need and I would not be very comfortable working at those heights). Is this viable?

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Re: Lean-to shed

Post by A. Spruce » Tue Jul 23, 2019 11:59 am

Yup! You'd have all the same concepts as before, only you'd be working with ledgers on both sides instead of just one. Sealing the roof against the wall may be a problem, but not insurmountable.
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