Single Pitch Roofs
Beardoh
| Posted in General Questions on
Looking for some thoughts on single pitch roof designs, similar to what is seen in this house shown in this AirBnB listing – https://bit.ly/4dbmTZM
Location: Climate Zone 6 – White Mountains, New Hampshire
Foundation: Slab (likely)
I like the look of this and think would work in the mountain east (I’ve seen it quite a bit in the mountain west of the US). It appeals to me from a practical side as well as both my wife and I would be more comfortable with working on a flatter pitch when we build.
What would the recommended minimum slope be for CZ6a?
When I play with different house depths, I realize that if we use too steep of a pitch, it makes the big wall too darn big. If anyone has any rules of thumb on width/depth of a building with a shed-style roof, I’d love to hear it.
Not sure if we’d go with roof trusses (to allow for blown in cellulose) or something different….but I am open to suggestions. We will likely have a wall bisecting a large portion of the house for support, if that matters to your comments.
By the way, I very much like the general design of the AirBnB in the link above, where there is a main house and then a suite, connected by a deck in between. I am thinking that to keep the overall project manageable and to get me a woodworking shop, I’d like to build a ‘Shop Suite’, where the auxiliary building has an office/guest-quarters and woodworking shop. We could build that building first, and be able to live out of the one-room suite while building the main house.
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Replies
I'd call that a "shed roof."
I have a "modern" house built in the 1970's in Rhode Island, one wing has a shed roof. See attached. I think it's about 10:12.
There's a couple of problems from a buildability perspective. First, there aren't standard flashings or treatments for the upper edge of a shed roof, the builder has to improvise a termination. It's really hard to ventilate properly, there isn't room at the ridge for a vent. I don't like not having an overhang on a roof -- that's also a problem on the side facing the camera.
As you mentioned, it creates a big tall wall. If you look at the vernacular architecture of New England such walls are rare, they're usually broken up with a skirt of some sort between floors. The reason is that big vertical expanses tend to leak in a driven rain. Not having an overhang makes it worse. This wall as originally constructed leaked quite a bit, we had it redone with 21st-century WRB and flashings, and it still leaks a little when conditions are right.
There is a 24" overhang on the lower edge, it wasn't original to the house but was added when we re-roofed.
Thanks for your thoughts and posts. I am not a fan of the no overhang designs. Do to a screw up by our framers on a house we built in '05, we had our gabled ends without overhangs. At the time, I just saw it as a deficiency. Fast forward after years of rain and replacing fingerjointed trim, I take it much more seriously.
I am thinking 2' overhangs minimum on all walls.
Beardoh,
Just like a gabled roof, the minimum slope is best kept at 3/12 or higher. I've done a bunch of them. Sheds, workshops and houses.
Think through how you intend to insulate before going too far. That may influence how deep you spec the trusses.
You don't have to have cathedral ceilings in every room. A variety of ceilings heights can allow for loft spaces, and also enclosed areas for mechanicals between the ceiling and roof.
As long as you have overhangs, the detailing of the flashing and ventilation is pretty straightforward.
A shed, a workshop, a house:
I like that your designs put an overhang on the uphill side. That's one of the things my house needs.
I was working in that center shop last week in heavy rain (enough to fill the 1000 Imp. gallon tank fed by the gutter in one day) with the door rolled up, and the ground didn't get wet within about 16" of the walls.
Thanks Malcolm - I am inclined to use trusses or I joists and insulate at the ceiling with blown-in cellulose.
Will do on the overhangs, I have watched to many Steve Baszek videos :). 24" minimum...maybe more. I realize that with the tall wall, there is a violation of some of his rules since that ratio of overhang to length to distance from top of the window gets screwed up.
I am considering something very similar (live in NH too) ...
I'd like to use SIP panels & hang the roof I-joists from the inside (off "top flange" hangers) if I could ...
Unity makes a nice shed roof house: the Zum
https://unityhomes.com/home-plans/zumette/
Here is a pretty cool "shed roof" house built out in my hometown that I stumbled across from BackyardEDU
https://www.youtube.com/watch?v=G-_gBAVCSS8
Thanks for those links. I had come across the Unity homes about a year ago and forgot about them...also in NH.
Where are you planning to build in NH?
Here's a slightly different take on the shed roof. This is Marcel Breuer's MOMA exhibition house, "House in a Garden". After the exhibition in New York it was bought by John D. Rockefeller and moved to Pocantico Hills, NY.
The two story section at the left has the master bedroom above and the garage below. The high ceilinged center section is the living area, and there are further bedrooms and utilities in the lower section at the right.
https://www.moma.org/interactives/moma_through_time/1950/houses-in-the-garden/
Very cool. I had not seen a home with the 'side sloping' mono pitch. Thanks for sharing.
JGSG,
My schoolmate Gavin designed this one. I wish I had.
https://www.affleckdelariva.com/en/projects/minton-hill-house/
Nice! That is beautiful
Beardoh,
One more for inspiration.
I call them mono-pitch or mono-slope roofs, mainly because "shed roof" sounds cheap. I have designed and/or built a few of them, including this one I designed that is just about complete now: https://www.instagram.com/p/CwlZV1IrL2Z/?img_index=1, https://www.instagram.com/p/C0wUad-rUOo/. They work well in specific situations but some of the detailing is challenging, and if you want two stories it's usually more efficient to build a gable roof.
Thanks Mike - A few questions pop up:
1.What is the pitch of the roof of that roof in the IG photos?
2.Could you mention some of the challenging details?
3.How was that roof insulated?
I am seriously considering a slab foundation - thinking about comments made in the PGH book :)
It's a 4:12 roof. Here in snow country I don't like to go less than that with a shingled roof, and this project had a very tight budget so we couldn't do a metal or membrane roof.
Perhaps the most challenging detail is client management! I had designed it as a single slope across the whole building, with a small areas on the high side carved out for a bedroom, bathroom and small yoga space. When my client saw the yoga space, she wanted to raise the already-framed roof. She got more space and loves that room, but ultimately couldn't really afford it.
Dealing with what happens at the high side can be tricky. The spans are fairly long so we used I-joists. It has R-60 dense-packed cellulose with a 1 1/2" vent.
This has a slab foundation over Glavel, the first time I used that detail.
Where do you put the vent on the high side? In the roof or in the soffit?
This is vaulted all the way to the peak, so the roof vents into the soffit space. We used Coravent vents directly behind the fascia where they aren't very visible. In fact the insulators wanted to know why they were installing Accuvents without eave and soffit venting!
Thanks Mike. I'd like to use metal roofing, and maybe drop to 3.5/12 pitch.
Sounds like tall I joists.
Glavel is new to me. Interesting stuff. For anyone else looking - https://www.glavel.com/applications/subslab-insulation/
Here is a photo of our current build. Slab on grade, R80 batt insulation with a 1-1/2” air gap below the roof decking. 2/12 pitch.. which is lower slopes than most. Metal roofing with hidden fasteners will be installed. It also has a peel and stick roofing membrane. Our overhang is 4’ on the front, and 2’ on the other 3 sides.
Cheers
Nice...big walls all around...thanks for sharing
Here is a venting and flashing detail that we will be following.
3:12 pitch seems to strike a nice balance between wall height and that nice monopitch aesthetic. Any lower than that, and you start limiting the choices for roofing materials, and possibly needing deeper-than-normal vent channels to promote airflow at low pitch. Much steeper than that, and that wall gets very tall very fast.
I'm also exploring these same types of wall height and roof pitch relationships, as I'm starting to design a big 3-car garage to complement my 1-car shed.
Here's another nice monopitch example, but uses a steel frame and wood beams because of all the lovely glass:
https://www.contemporist.com/an-extended-sloped-roof-runs-the-length-of-this-modern-home/
I do like the common monopitch house layout of having the tall ceilings and common areas at the tall wall side, and having the closed-in bedrooms at the low wall side where things can be more cozy, and maybe a central hallway to divide those two areas.
A vented peak cap on a standing seam metal roof is pretty straightforward.
The Z-channel that forms the closeout between the roof panel and the peak cap is perforated, so the peak cap is functionally identical to one half of a vented ridge cap on a gable roof. Different roof manufacturers have different levels of sophistication for that detail; some advertise much better control of wind blown rain/snow, etc. by using a second "dam" of bent metal against the roof panel, or a more labyrinth venting path. Again, same variety of solutions as on a gable ridge cap.
I have that detail on my shed, but ended up doing a hot roof so I used non-perf Z closure and don't have a vent channel in the deck sheathing.
The shed below is 3:12 pitch. How do you get experience with rainscreens? Practice the standard details on a shed.
I know the OP question was about roof pitch, but there's also talk in the thread about monoslope roof venting. Why not use the system explained in Martin H0lladay's article here (https://www.finehomebuilding.com/project-guides/insulation/insulating-unvented-roof-assemblies)?
I'm curious, rather than suggesting since I'm doing a monoslope roof design as well.
Tizano,
There is nothing wrong with it. It is included as one of the five common roof assemblies we know work in Martin's article: https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work
I used it on the backyard studio I built this summer in the attached photo. Compared to the much simpler assembly #1, it is expensive, harder to build, detail and sequence - and as we have discussed in your floor assembly thread, relies on good weather to install.
That looks really good Malcolm! Thanks for sharing the images. It's nice to see the rafter in the first image which better explains the rafter tails to me. In the second, it looked like they were scabbed on.
Anyway, mine is similar (as you likely gathered :)).
Tiziano,
Attaching that last rafter outboard of the sheathing makes the detailing a lot easier, both at the corner, and at the top of the siding.
Disclaimer: The client insisted on the colours.