Help me frame my shed style roof

[justinadams02]

Hello!

I am finalizing plans on a detached garage/office for my back yard. I’ve had some initial plans drawn up by an “architect" on Fiverr.com based on my own design. I'm just flying by the seat of my pants, but these drawings have gotten me through the plans review process with my city and also given me a way to get bids from trades and materials. I was originally going to hire everything out, but after getting dozens of bids it looks like I will need to attempt do everything I can on my own to keep the price tag reasonable. The price of lumber and labor seems to be pretty high right now.

The concrete, stonework, garage door, spray insulation, some electrical, and plumbing rough-in will be hired out. I plan on framing the building and putting up an R-panel or standing seam roof myself. I am going to have to re-submit my plans to the city for some concrete slab detail changes and would like to get any other revisions done at the same time.
I have never framed anything before and while I’m excited about learning along the way I also want to eliminate as many mistakes as possible before I get going. I have some questions.

My building is not square. I tried to maximize the space of my non-square fence line while also adhering to the required setbacks in my zoning ordinance.

I went with a shed style- vaulted roof because I like the look and it seemed like it would be simple, but trying to figure out the roof framing is proving difficult. There’s plenty of videos and literature out there that discuss framing a shed roof over a square building. I’m trying to adapt these to my footprint.

Is there a framing system out there that will work for the roof on this thing or should I scrap the plans and some square footage and go back to a rectangular building? The wall that will be at an angle is giving me fits. Should I keep the rafters perpendicular to the top-plates on the North/South walls and try to make the ones on the east side of the roof rest on the side wall with some very fancy birdsmouth joints? Should I try and angle the layout of the rafters to fit the foot print? “Lookouts” notched in the interior rafters look promising as a way to support parts of the “flying” rafters/ fascia.

I have been told that these 2”X12” rafters will sag quite a bit across this 22.5’ span. I don’t have to worry about snow load. I’m at a 1/12 pitch now, will a 2/12 pitch reduce sagging? Should I look into using wooden I-joist for this span? Maybe even steel? Is there a way to reduce the span without adding columns and breaking up the open floorspace?

Any advice, direction, or encouragement is greatly appreciated!

 

[ducatithunder]

I joist would work well for this. Give you the clear overheard. I dont see why the wouldnt work for a skewed building. Once these are boxed the joist become very sturdy. With your layout the center wall would have to be load bearing. I used Ijoist for my garage. They were installed on 12 inch centers. The joist were Nordic NX-40 which are 14inch tall. I cut down the ends for a modern look and to thin out the fascia. The roof is stout. Same 1/12 pitch with a 28ft span wall to wall. These were very easy to work with. I designed/built my garage pretty much on my own with heavy lifting help from others when needed. Feel free to PM me if you have any questions.

 

[Hank11]

I think just go back to a square building. The additional space won't be worth the additional cost of the more complicated building process. IMO.

ducatithunder's build is pretty great. Your's looks nice too. Good luck!

 

[ducatithunder]

BTW ... right now with lumber prices through the roof, is a terrible time to build a garage unless absolutely needed. If you wait out this storm you will def recoup alot of money with you as the builder and cheaper building material prices. I commented at Lowes the other day how Im glad my building was finished prior to Covid when I saw the price of studs and sheathing. Lumber prices have doubled if not tripled in my area. The cost savings for DIY will be null and void by the lumber market.

As for the standing seam roofing ... here are my thoughts. I went back and forth on doing my roof install myself. I had to do standing seam due to the 1/12 pitch. I had covered the entire roof with ice and water shield to buy me the time needed to get the roof up and protect the sheathing. I decided to just hire it out as my work schedule and free time were clashing. Having a couple buddies help with lifting walls is a far cry from assisting with putting up standing seam, even the click lock style. Materials were roughly 4-5K. I hired out the job to professionals. 2 days and 19K later I had a very nice standing seam roof installed. Hindsight ... best decision of the build. My panels were roughly 36ft long since the front and rear overhangs add 3.5 feet on the front and 2 feet in the rear. They rolled the panels on site. I watch 5 guys struggle with those panels for 2 days and a thunderstorm half way through. The roof was perfect when they were done. Providing the DIY labor def allows you to make take funds saved and apply it to other areas. Im sure I could have done it but it would have taken at least a week or longer and most likely wouldn't have looked as nice nor had any warranty associated with it.

 

[TractorJeff]

2x12 on 12 inch centers shouldn't be a major sag problem? You did say there is no snow load? Metal Roof is a lot lighter than a Shingle Roof.

 

[justinadams02]

2x12 on 12 inch centers shouldn't be a major sag problem? You did say there is no snow load? Metal Roof is a lot lighter than a Shingle Roof.

I am in North Texas so it looks like we are at 5psi.

 

[justinadams02]

BTW ... right now with lumber prices through the roof, is a terrible time to build a garage unless absolutely needed. If you wait out this storm you will def recoup alot of money with you as the builder and cheaper building material prices. I commented at Lowes the other day how Im glad my building was finished prior to Covid when I saw the price of studs and sheathing. Lumber prices have doubled if not tripled in my area. The cost savings for DIY will be null and void by the lumber market.

As for the standing seam roofing ... here are my thoughts. I went back and forth on doing my roof install myself. I had to do standing seam due to the 1/12 pitch. I had covered the entire roof with ice and water shield to buy me the time needed to get the roof up and protect the sheathing. I decided to just hire it out as my work schedule and free time were clashing. Having a couple buddies help with lifting walls is a far cry from assisting with putting up standing seam, even the click lock style. Materials were roughly 4-5K. I hired out the job to professionals. 2 days and 19K later I had a very nice standing seam roof installed. Hindsight ... best decision of the build. My panels were roughly 36ft long since the front and rear overhangs add 3.5 feet on the front and 2 feet in the rear. They rolled the panels on site. I watch 5 guys struggle with those panels for 2 days and a thunderstorm half way through. The roof was perfect when they were done. Providing the DIY labor def allows you to make take funds saved and apply it to other areas. Im sure I could have done it but it would have taken at least a week or longer and most likely wouldn't have looked as nice nor had any warranty associated with it.

I am praying lumber prices go down some before I start putting it together. Just getting the site prepped and slab poured will probably stretch into the spring with the rate I am going. We are having our 2nd boy in May so I will be kicked out of my home office at some point and will need the space.

I may try and do the 1 on 12 roof in R-panel because I feel like it will be far less visible than the south facing 4 on 12 face. I had a quote for 10k to installed R-panel professionally on the entire thing. I think I figured the materials would cost me about $800 (without sheathing)

 

[justinadams02]

I think just go back to a square building. The additional space won't be worth the additional cost of the more complicated building process. IMO.

ducatithunder's build is pretty great. Your's looks nice too. Good luck!

Thank you!

I will likely end up going back to rectangle. I think I only lose 70+/- square feet. If I can find a way to do it somewhat painlessly with the current plans then I would like to.

 

[justinadams02]

I joist would work well for this. Give you the clear overheard. I dont see why the wouldnt work for a skewed building. Once these are boxed the joist become very sturdy. With your layout the center wall would have to be load bearing. I used Ijoist for my garage. They were installed on 12 inch centers. The joist were Nordic NX-40 which are 14inch tall. I cut down the ends for a modern look and to thin out the facial. The roof is stout. Same 1/12 pitch with a 28ft span wall to wall. These were very easy to work with. I designed/built my garage pretty much on my own with heavy lifting help from others when needed. Feel free to PM me if you have any questions.

I Tried to PM you ducati but I have to get my post count up a bit first.

Your build looks awesome. I like how you cut down the ends of those joists.

How did you attach the pieces perpendicular to the rafters (Lookouts maybe). Are there brackets for that connection? Also how did you attach your rafters to the top plates?

I'm wondering if I can keep my rafters perpendicular to my north/south walls and use lookouts of increasing length to span the gap created by my angled east wall.

 

[ducatithunder]

I

How did you attach the pieces perpendicular to the rafters (Lookouts maybe). Are there brackets for that connection? Also how did you attach your rafters to the top plates?

I'm wondering if I can keep my rafters perpendicular to my north/south walls and use lookouts of increasing length to span the gap created by my angled east wall.

Thanks. Lots of planning then re-planning, lol. I blocked out my rafter ends based on the nordic Ijoist recommendations. They have a downloadable "book" that calls out what you can and cant do. Each joist has a 2x6x8ft board clinch nailed to support the cantilever. That also give the face to nail the subfacsia to and a nailer on the edge for attaching the T&G soffit. Ill post a picture if I can find one.

They make an adjustable bracket for attaching the joist to the top plate. They are hard to find and rather expensive. For a roof with more slope then 3/12 they work well. For the 1/12 roof you can build a bearing plate. On top of the top plate I have another 2x6 that is beveled to the degree needed for 1/12 roof pitch. I chose the bevel plate as with a low slop there is much more contact on the wall for support. This is another nordic approved method. I would download the book and see what you can do. Find your local joist distributor. I had weyerhaeuser and nordic that were available local. The Nordic supplier gave me a much larger discount. Either brand is good.

As for extending the eave or lookout, IIRC you should be able to extend out 4 ft with the way I blocked and supported the I joist. I can post a picture of the joist when I cut them and built them out. The sides are blocked and keyed into the web of the main joists. You just need to keep and eye on how much overhang you have. I did mine based on snow load and wind. You may only have to worry about wind. Based on your drawings you should be more then adequate for that span and Ijoist.

If you end up squaring up the back wall and keep it at the 21-22ft your garage may not be very deep. Mine is 28ft deep by 46 wide. I have another garage attached to my house so this is not my main garage. More for the "other cars", car lifts, and workshop. I would suggest that take a look and if you can deepen the garage to 24ft or deeper vs having the extra 70sqft of the skewed wall and complexity, unless its done that way for curb appeal or to match your house. It almost appears you have it slanted based on the setbacks for the property?

 

[justinadams02]

@ducatithunder - Yes I am hemmed in by set backs and proximity to the main house. Sadly I can't go any deeper on this property. This will give me practice for when we have some more space.

I taped out the dimensions on my living room floor of the space I would lose by squaring off the east side and starred at it for awhile to try and decide how much headache it was worth. It mostly confused my dog.

I will be tracking down a joist distributor tomorrow. I've got to figure out how much detail the city needs if I go that route, and how to communicate the joist system to my Nigeran architect on Fiverr so I can get it drawn up. Thank you for the advice.

 

[ducatithunder]

@ducatithunder - Yes I am hemmed in by set backs and proximity to the main house. Sadly I can't go any deeper on this property. This will give me practice for when we have some more space.

I taped out the dimensions on my living room floor of the space I would lose by squaring off the east side and starred at it for awhile to try and decide how much headache it was worth. It mostly confused my dog.

I will be tracking down a joist distributor tomorrow. I've got to figure out how much detail the city needs if I go that route, and how to communicate the joist system to my Nigeran architect on Fiverr so I can get it drawn up. Thank you for the advice.

No problem. Enjoy the build. Im sure your wife will be tired of you talking about the details of the build a week from now, I know mine was. I had a basic hand drawn scaled drawing. Called out stud spacing, doors, headers, materials, elevations, and basic footings. It was very very basic. As for the joist, when you talk to the distributor they should have an engineer on site that can load the joist for you base on your span etc. Youll have a stamped drawing for it to give to the city. Try not to over complicate it. The city should have the required callouts and details you need to provide at your zoning office. Sometimes less is more, especially when permits and the city are involved. Just make sure that the engineer involved with your roof design, concrete, and load bearings gives you the details and its stamped. That middle load bearing wall might need an engineering stamp based on the height. In my county anything over 12ft needs to be reviewed by an engineer.

 

[Voi]

My cabin here in the Black Hills has a 2/12 pitch, 20' span with 12" I-joists.

No interior load bearing walls. I don't recall what our snow load rating was.

We did a structural steel, exposed fastener roof that is rated down to 1/12.

Vapor permeable membrane on roof sheathing.

3.5" closed cell on underside of roof deck. Then blown in fiberglass.

Didn't have a chance to read the thread. Let me know if you have any questions.

If I could do the cabin again I would have used structural Glulam beams on 10' centers and then done purlins on edge.

 

[justinadams02]

@Voi - What made you go with the I-joists over 2X12s for the 20' span? I found out today the joist would run about $600 more than using dimensional lumber for my project.

Using the Glulam beams what would you run as purlins? I'm envisioning something sitting on top of the beams running perpendicular to them?

 

[Voi]

@Voi - What made you go with the I-joists over 2X12s for the 20' span? I found out today the joist would run about $600 more than using dimensional lumber for my project.

Using the Glulam beams what would you run as purlins? I'm envisioning something sitting on top of the beams running perpendicular to them?

Went with I-joists for snow load & ease of installation. Although after bevel ripping both top plates, cutting filler for hurricane clips & installing said clips the only advantage was the light weight of the I-joists.

My plan was to use 9" tall I-joists perpendicular to the beams. It's a seasonal cabin so I didn't need to meet code for ceiling insulation. 9" would have been enough.

Long story as to how that didn't happen but it's one of my few regrets.

There is a build in the gallery section that used that method. Up in Canada, IIRC.

 

[TRWham]

Have you considered steel bar joists?

 

[CraigStu]

I like what you are looking to do except for the angled wall. That is definitely an extra difficulty that would cost extra to have done by a contractor. For someone w/ limited experience (I am in that category too) trying to do as much as possible himself, I wouldn't even consider it.

 

[justinadams02]

@CraigStu - Yes the skewed wall still has me nervous, but after talking to the lumber guy (family friend) at length yesterday its sounds like it's something I can tackle with some patience and help. At this point I am going for it. I'll be cursing myself when I'm on the roof trying to cut my r- panels I'm sure.

@TRWham - Steel was the first thing I thought of as a rafter alternative and will likely dig into the possibility a bit more before I pull the trigger on the 2X12 rafters. I will compare cost and figure out if the city will let me do a steel/stick hybrid without an engineers stamp.

 

[firebirdparts]

The skewed wall is kind of interesting because the height will be varying at a rate that is not the decline of the rafters, but that's not really that confusing. When you build something yourself, if a 2 x 4 is too long you can just cut it again. Your time is worth $zero.

Those short rafters are going to look funny landing on the wall at a 5 degree angle, but you'll cover all that up. The rafter plan, as shown, is infeasible, but oddly enough the straight side is much worse. Overhang that doesn't just occur by rafters hanging over has to be "finagled" on any building.

Seems like bar trusses are very far over the line into overkill.

 

[Hank11]

I kinda like the skewed wall but its will be skewed at every step of the process right down to trim work, making the whole project take longer. Maybe a lot longer. If its square, you know what to do and how to cut and fasten everything. Skewed and its all funny angles and some funny compound angles. A square version of your build in the simplest roof form you could have. Add a "ladder" each side for even overhang all the way around and that part is done.

Look at ducatithunder's first picture. See all those side extensions or tails at top right that form the overhang? Imagine doing that on a skewed roof where each one is a little different. Ugggh.

 

[Cypress]

I joist would work well for this. Give you the clear overheard. I dont see why the wouldnt work for a skewed building. Once these are boxed the joist become very sturdy. With your layout the center wall would have to be load bearing. I used Ijoist for my garage. They were installed on 12 inch centers. The joist were Nordic NX-40 which are 14inch tall. I cut down the ends for a modern look and to thin out the facial. The roof is stout. Same 1/12 pitch with a 28ft span wall to wall. These were very easy to work with. I designed/built my garage pretty much on my own with heavy lifting help from others when needed. Feel free to PM me if you have any questions.

I just wanted to stop in to tell you that you have a very beautiful structure there sir. Well done!

 

[TRWham]

...
Seems like bar trusses are very far over the line into overkill.

I don't think so. Bar joists on wide (maybe 4') centers with a steel roof deck with foam and a membrane or maybe SIPS with a metal roof over would make quick work of framing this. This building has design characteristics of commercial structures so perhaps a few common commercial construction methods would help.

 

[ducatithunder]

I just wanted to stop in to tell you that you have a very beautiful structure there sir. Well done!

Thanks for the kind words. Its still a work in progress, but isnt everything.

 

[justinadams02]

Update!

I had the slab poured this past spring. Skewed design is set in stone (concrete) now. I tied into the copper water lines under the existing house's slab with copper transitioning to PEX out to the new garage. I also had plumbing for a couple of sinks and a bathroom roughed in and conduit for electrical ran through the slab.

Everything was permitted , ready to frame...then lumber futures hit the moon and I put this on the back burner.

Prices are back down and I am ready to go again. I have a question about insulating the roof.

This will be an open-rafter ceiling over an unvented space. Decking will go over the rafters then I will cover the decking with R-Panel or Standing Seam. I would like the option to condition the space. I live in north Texas. Its awful hot and humid.

How should I insulate the roof? The two contenders seem to be spray foam between the rafters or rigid foam between the decking and the metal with ventilation through gaps between 1X4's sandwiched in. I don't have a full grasp on how to prevent condensation and provide good insulation from the Texas heat.

 

[nadogail]

I have some time to help, I can bring all my own tools for framing a house, shed or garage. Where are you located? and if I will be away from home for more than a day do you have a place to lay my head down at night?

 

[justinadams02]

I have some time to help, I can bring all my own tools for framing a house, shed or garage. Where are you located? and if I will be away from home for more than a day do you have a place to lay my head down at night?

This would be great. I'm afraid it may take longer than a day but I do have some extra pillows

 

[nadogail]

Where is the job?

 

[justinadams02]

Where is the job?

Fort Worth, Texas