Water Management Without Overhangs
TCH2001
| Posted in General Questions on
I am building a design driven modern / contemporary home with no overhangs. It is less than ideal without the overhang for water protection on the siding, etc but looking for advice on the best way to protect the underlying structure.
Current plan is shingled roof with synthetic underlayment and OSB sheathing with traditional house wrap and hardi lap siding.
Any insight on preparation at roof/wall connection or siding installation to reduce potential water issues?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
TCH,
First of all, can you tell us your name? (I'm Martin.)
Water-management details aren't optional, in my book. Your plan is unwise.
"It looks cool" shouldn't trump "roof overhangs protect your siding."
For more information, see this article: "Every House Needs Roof Overhangs."
+1 on what Martin said. Even a few inches of drip edge would help. The roof underlayment should probably overlap the wall WRB. Maybe Zip with a liquid WRB and StuccoWrap. Hardi with treated wood furring.
Martin and Jon are right that a roof overhang is the best way to protect the siding. I can understand not wanting one with a flat roof, but the sloped roof without overhang I never understood. There is also no gutter in the detail, so you will be effectively routing rain down your wall. There is no good way to make that last.
There are some alternatives that are employed when constructing tall buildings where overhangs are useless, but you'd have to use the types of cladding found on such buildings.
There are other ways to implement overhangs that might fit your aesthetic better, like porches, balconies, or awnings. It will only be partial protection, but it is better than nothing. Windows and doors will always be weak points, so sheltering them helps. Besides, it is nice to be able to unlock the front door without getting wet.
Gun to my head, I would detail the wall like a roof. Peel and stick membrane on the whole thing, and a rainscreen. Add at least a little drip edge too, so the roof runoff is directed away from the wall. I'm not sure it would help, but I would consider making the rainscreen a little larger than usual -- maybe 2x4s as the furring strips. Treated wood probably isn't necessary, as there should be enough drying potential in the rainscreen. If there isn't, you're screwed anyway.
At the very least, don't build like this in a high rain area like the pacific northwest. If you are getting mare than 30" of rain a year, you are probably going to wind up in trouble. But you would be fine in a desert.
You're going to need to work on your insulation strategy along with your desire for no overhang. I agree with rainscreen and continuous WRB on roof overlapping walls. What zone are you in? Rain and ice is going to be tough on siding and openings. Maybe synthetic stucco?
Just so happens there's an ad just to the right of this response! "Slate Rainscreen cladding". No overhangs.
What's a "design driven" house?
Malcolm,
I'm just guessing, but I think the phrase means something like, "The project has an architect who is more interested in making a bold visual statement than in issues like water management and durability."
I've seen plans for buildings like this with a drip edge that extends maybe 3-4" out to provide the function of a bit of an overhang with a different aesthetic. That would be better than nothing. I haven't seen it in person to know how it looks or how well it works.
If it's not too late to add eaves, this blog post has a few images of pretty minimal/contemporary looking homes/cabins with eaves that still have a similar aesthetic feel to an eaveless design: https://www.project-o.fi/post/the-overhang-2
Are you the owner, contractor, designer, or some combination of those?
If you're committed to the eaveless design, I wonder if you get get whoever is driving this design-driven process to come up with a really cool looking custom gutter.
Making the overhang thin is somewhat appealing from the perspective of avoiding thermal bridging through protruding rafters. But problematic from the perspective of snow and wind load on the overhang--depending on length and loading, it might require steel support.
Some flavors of modernism aim to value functional forms over ornate forms. I think it's tragic that people who espouse that value failed to follow up with sufficient study of functionality to understand which features of traditional architecture are functional and which are ornamental. And so we end up with the choice between architecture that adds features and undermine functionality, or architecture that omits the features the provide essential functions--the two options illustrated by the photos linked in comment 16.
Yeah, it definitely seems like it would be wise to have an engineer take a pass at the super thin overhangs to confirm they stand up to the local wind and snow loads.
Regarding "form ever follows function" I think it's interesting that that phrase came from Sullivan's essay "The Tall Office Building Artistically Considered" which, to grossly oversimplify it's points, is about decorating the exterior of an office building to symbolically communicate the functions of those interior spaces.
Not really making a point here, just food for thought ;)
https://ocw.mit.edu/courses/architecture/4-205-analysis-of-contemporary-architecture-fall-2009/readings/MIT4_205F09_Sullivan.pdf
These folks show some decent details for hidden gutters. Adding in gutters would make the siding last much longer. Option 1 would work best in your case.
http://blog.buildllc.com/2012/09/case-study-house-status/
Lot of those modern houses look great in pictures, but nobody shows how they look 5 years down the road. No overhangs is overall a bad idea unless you have metal siding.
My first inclination would be to take Brendan's advice and try and find a design whose aesthetic you like with overhangs. But I think your link is interesting. As you point out: whether you could make it work without metal siding is an open question.
Ask Hugh Newell Jacobsen's firm how they do it. Every house he designs has that detail. BTW, this is not one of his:
An A-frame building is a roof without eaves. So as Aedi says, treat the walls like a steep extension of the roof and it could work.
Jon,
An A-frame has eaves. (The eave is the bottom edge of the roof, where the water drips off the dripedge.)
The eaves of an A-frame may only be 10 inches above grade, but they are still eaves. And it should be noted that the eaves of an A-frame shouldn't dribble water down the foundation wall -- the eaves of an A-frame should overhang the foundation.
Well, I am all for design forward. So I'm with you on this. The hard part is balancing good practise, durability, cost and ease/willingness to build.
I hate the look of eavetroughs. Infact I designed and built concealed gutters on my current build (flat roofs). So I agree that a no eaves look is very sharp.
Apparently the main concern here is water, so the question is how do you design to manage that?
For the roof, maybe consider at a recessed gutter. Here's a fun example detail I found. https://goo.gl/images/njUv98
I'd also suggest a better roof system like maybe a galvalume roof with an air gap and peel and stick roof underlayment.
Also, I would personally splurge on a better wall assembly. Since you're not doing exterior insulation, I'd suggest a peel and stick for the WRB as well, Hardie is not my favourite since it absorbs water but as long as it can dry I think it should be fine. pay extra attention to your fenestration details as you would probably see more water exposure than usual with overhangs.
Also a major consideration is your basement detail which you haven't shown us. Having good soil drainage, good foundation waterproofing membrane, drainage layer and an exterior foundation weeping system is important to prevent water and moisture problems.
I'm no expert, so take my optimism with a grain of salt, for what it's worth.
Jamie
i'm not trying to be annoying, I really don't understand. How does what has been termed a "design driven" or "design forward" project differ from others?
Malcolm,
If you'll allow me to be so bold to say here is the difference:
If it looks like this:
https://img-aws.ehowcdn.com/600x600p/photos.demandstudios.com/getty/article/171/191/86516703.jpg
Or it looks like this:
Image 2
The first one is a conventional design, the other one might be considered "design forward"
Ah - so it's an acronym for Contemporary Modernism.
I hope those are not my only two choices.
The pile of gables in the first example is also design driven, just driven poorly as those extra roof details serve no real function.
Having owned a house that has no eaves I would never own or build another one unless it was flat roofed. The one I bought was designed from some Better Homes and Garden plans from the 80's I believe. Very tall, 12/1 roof and lots of vertical wood siding. It was 25 years old when I bought it and the siding was toast. Water came off the roof and ran down the walls. It got behind the paint and bubbled it. Then it damaged a lot of the wood. No gutters except for over the rear door.
Mick
Malcolm Taylor posted this example of an overhang-less roof in another thread:
https://architizer.com/projects/perfect-wall-house/
Notice the gutter, and the awnings over the (first floor) windows and doors. Not only do they protect the walls at the most vulnerable points, they reduce glare from the sun and unwanted summer heat gain. While the second floor windows are pretty exposed, the dormer is literally constructed out of the same materiel as the rest of the roof. The windows are also "innies", providing further protection. The home still manages to look quite modern.
I'm planning a build similar to this house you posted in #23. 2x4 construction, exterior insulation, metal roof and siding. I'm trying to get more info on how to detail the drip edge and add the gutters in a house like this. Any pointers anyone?
Here is a Matt Risinger video of the h0use construction:
https://www.youtube.com/watch?v=hTwq-qUnr9I
I'm late to the party, but my house is a traditional version of the one in the link in #23 above. There's no overhang/soffit, but on three sides, I have a 6" wide half-round gutter system. That keeps the roof runoff off of the siding, and the siding seems to handle direct rain without a problem.
The lack of a gutter or overhang on the back (as in #23's link) does mean that the windows on that wall get more direct rainwater, and I've had some minor moisture problems with the wood windows as a result. (They weren't well-painted by the builder and the recurring wetness from rain caused some water damage to underfinished wood.)
I am about to add Bahama shutters to the windows on that gutterless wall, which also faces west, so I'm getting sun protection in addition to a rain shield on the windows. That works functionally and aesthetically on my house in the tropical south.