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Garage lean to ideas

Started by sbishop, April 14, 2021, 09:39:52 AM

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sbishop

Hi everyone, its been a while and i'm hoping everyone is doing well. I got the ok from the boss to build a lean to on our garage and i'm looking for ideas on the layout. The only way i got approval was to build the wife a craft room within the lean to. I need a place to store 2 atv's, 4 bycicles, some bin's etc. i'm guessing i will need 2-3 divided rooms. i'm planning on removing the existing windows and incorporating them into the lean to if it makes sense, i could use one of those openings as access to the craft room. Any suggestions on the layout?

my existing walls are 10'5" and i would like the lean to be 12 or 14ft wide about 22 ft long (from the first window to the back of the garage). what size rafter would work as i get a lot of snow and this was my first year with the metal roof on the garage and it didn't slide off as the metal has a texture to it (which i liked, didn't have to clean up the snow). i'm planning on pouring a cement slab

any help is much appreciated with the layout.

Thanks
Sbishop









btulloh

Love adding leanto's. You might as well add one on each side while you're at it.  :)  

Your drawing looks like the new roof is the same pitch as the existing roof. With ten ft walls you'll need a lesser pitch, but you're probably already factoring that in. Maybe even better to attach the new rafters on the existing roof rather than extending from the eaves. Lots of variables and choices.

Can't really speak to layout, but no doubt that will be driven by your needs for the new space. And your bosses' mandates.  :D

Have fun.  Can't wait to see how it evolves.
HM126

sbishop

i've already got plans for the other side lean too, i would like to have a roof over my utility trailer. i might just get the cement post dug and poured at the same time, that way i could work away at it when i have time.

i'd rather just attach the rafters to the side of the wall and not mess with anything on the existing part of the roof, i think it will be less hassle for me. i'm thinking at the far end of the lean to there will be enough height to get the atv's in, just need to figure out what of roll up door i could install. the drawing of the lean to was just for show..i'm not a good person to draw..ha

thinking maybe something like this, that middle wall could help support to roof?






mike_belben

Biggest thing i can tell you is that the flatter your roof pitch the more important a drip edge becomes.  A really flat pitch will have water cling, walk back up and drip on the lumber.  And as mine is nailed, i cant unfasten the tin to correct my mistake.  Flat also requires sealants to keep the melting snow from damming backward into the seams and laps. 


Dont skimp on whatever is locally the best method to prevent condensate from dripping off the interior side of the tin.  Here its a wrap of some sort but im in the south and too poor to have ever tried it but condensate underneath is a major concern.
Praise The Lord

sbishop

i'm planning at least a 3 / 12 pitch but i'm thinking i'll push it to a 4/12. i don't really need 8ft wall on the far end, just enough height to get the atv's in and shut the door.

if it was a 3/12 pitch and lean to is 14ft long attaching to my outside wall which is 10'5" i'm guessing my fartest wall would be approx 7ft tall (minus the width of rafter size). if i could get above 6ft i'd be happy.

but then i would have to find a roll up shed door to fit in that space.


mike_belben

Dont discount barn doors or rail type sliders if it solves other issues.  


I cant tell you what pitch problems start at or are fixed by.  I would want @Don P  opinion on it.

I know from experience now.. That cruel teacher...  1/4" per foot has major issues with snowmeltxand edge drip.  but it beats standin in the sun and rain.  If i have no roof give me a leaky one to work with!

Praise The Lord

69bronco

Quote from: sbishop on April 14, 2021, 11:26:43 AM
i'm planning at least a 3 / 12 pitch but i'm thinking i'll push it to a 4/12. i don't really need 8ft wall on the far end, just enough height to get the atv's in and shut the door.

if it was a 3/12 pitch and lean to is 14ft long attaching to my outside wall which is 10'5" i'm guessing my fartest wall would be approx 7ft tall (minus the width of rafter size). if i could get above 6ft i'd be happy.

but then i would have to find a roll up shed door to fit in that space.
It's been awhile but wouldn't a 4/12 starting at 10' leave you 6' at 12' wide?

Don P

4" drop in every foot is 56" shorter 14' out + rafter plumb depth + door header thickness, its getting around 6-7' shorter... I think you're getting too short. Going to a minimal pitch down below is risking meltwater backup inder the transition. Myself I'd probably look at removing the metal and crawling up onto the existing roof with the transition pitch break. You can run supports from the wall up to the underside of the new rafters as they cross the existing wall to keep from overloading the existing trusses. At that point it would make sense to go with a full 8' height wall outboard if possible. Just as a reminder never tag rafters onto an overhang, dig in and support them back at the wall either on a ledger or preferably on top of the existing wall.

mike_belben

Don whats the issue with sistered overhang rafters?
Praise The Lord

Don P


mike_belben

i sistered on my lean-to extension this year.. SYP 2x6s with a full square of overlap.. so maybe 5.25x5.25 ish.. and i think 6 ribbed nails each from two directions, they were C clamped in place real tight first to get them on line with the string.  no light gap in the coincident faces.

 once the floor is poured im gonna put a framed wall under the lap of the two rafters and remove the carry beam of the first segment, thats about 8 inches away at present.  the only goofy thing is theres gonna be some odd snowblocking just hanging around randomly.  i didnt initially think i could get the grade low enough and draining to have any pitch on a 12' extension but its working out well enough.

smiley_swinging_board

i put hurricane ties from beam to rafter on each one, with every single hole filled with #10 galvy nails, just incase you ever pop in and scrutinize someday.  i dont wanna catch too much FF flak on my retired hobo camp.  ;D



smiley_inspector
Praise The Lord

peakbagger

To ruin your day, structural code usually requires that if you go with a shallower pitch on the lean to you create a low spot that can be a high snow load area. I do not claim to be a structural PE but I think the lower roof needs to be structurally sized for a higher load than the primary roof. It may be 30% increase but its been awhile. 

sbishop

Hi everyone,

Finally getting around to making this lean to happen. I poured the slab at the end of May but the weather got hot and lumber prices were crazy so things were on hold till a month ago.

i'm trying to figure out if i'm going to have a problem with condensation from the metal roof. there is a 12X12 room at the back of the lean to will be insulated and heated, rest of the lean to will not be heated or insulate. The metal roof was installed on 1x4 purlins so it is exposed inside. 

How would one deal with condensation dripping from the metal roof? my plan was for batt insulation, vapor barrier and drywall. Any idea if i will have issues? should i install ridgid insulation instead? Thanks for any help

Sbishop





Don P

Is there any provision for venting it from lower to upper end and out? If not sprayfoam would probably be best, seal the condensing surface. A lot depends on how wet an area is below it. Plastic under the slab? 

metalspinner

The metal roof on my pole barn rained condensation down until I spray foamed it.  You will get lots of moisture from the concrete curing ,too. 
I do what the little voices in my wife's head tell me to do.

sbishop

The only venting is between the purlins from the soffit . The slab does have 1" ridgid insulation and vapour barrier .

This area will have some heat from my garage as I can leave the door open into my garage . I keep it around 10c 

What if I was to put ridgid insulation up against the Purlins and then bat insulation below it. Overkill or that wouldn't help?

Thanks 

Chuck White

Earlier this Summer I hired my neighbors to remove the steel from my garage roof, solid board the roof, cover with felt paper, then install new steel!

The dripping QUIT!
~Chuck~  Cooks Cat Claw sharpener and single tooth setter.  2018 Chevy Silverado and 2021 Subaru Ascent.
With basic mechanical skills and the ability to read you can maintain a Woodmizer  LT40!

sbishop

Hi Everyone,

Wanted to let you know that the outside is completed, working on the crackfilling for the 10X12 "She room". other room is completed for now, not insulated yet, probably next year but its dry and has our two ATV, snowblower and lawn tractor!






SBishop

sbishop

Hi everyone,

i'm looking at adding lean to on the other side of my garage but this side will be open. Just looking to have a roof, maybe enclosed and slab in the future but for now a roof.

I had 4 foot tubes installed when i was building the lean to on the left side of the garage and got them filled when the cement truck was here. My question (s) is will 6X6 spruce or hemlock be big enough for the post? also what size top plate should be? Anyone have a calculator?

Thanks for any info.

Sbishop


beenthere

Answer will depend on how the rest of the framing is anchored to the existing building. If only downward load on posts, should be adequate size. If bending forces possible, then need to calculate what the moments may be, and how the top joints are fabricated. What is the plan for "on top of" the posts? Trusses?
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Wlmedley

I built a similar addition on the side of my garage several years ago. I used 4x4's for posts and used 2x6s with 1/2" plywood samwiched between them stood on edge on top of the posts.Later on I poured a floor,layed a row of 4" block between posts and framed up conventional walls between posts.Everything was even and it made it easier to finish interior and exterior walls.My wall length was 30' and I haven't had any problems.
Bill Medley WM 126-14hp , Husky372xp ,MF1020 ,Homemade log arch,Yamaha Grizzly 450,GMC2500,Oregon log splitter

Don P

Half the 11' rafter is supported by the existing building, that's a detail as well. The other half plus the overhang is supported on the outer post and beam you're asking about. Call it 7' x 10' post to post = 70 square feet. I took a stab based on Maine and called it 120 lbs /sf x 70 sf=8400 lbs total load. Check your snow load

Calc is here, I'm assuming you will build it up of several plies of 2x lumber; 
Design for Bending (forestryforum.com)

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