Roof slope for heavy snow load

We would like to build a modern house in New Hampshire (one story, 40’ x 86’) with a 1/4" slope roof. The roofing company our contractor uses refuses to warranty a roof with this pitch because of snow load. I see many other roofs with minimal pitch in cold climates, included the Flatpak prefab and many others. Are none of these roofs warrantied, or is this a problem only with this particular roofing company? Our contractor wants us to change the design to a 1/2" inch pitch – we don’t want this. Suggestions, info most welcome.

are you saying he wants to decrease the pitch? 1/4 to 1/2 (4-12 to 2-12) or is it a typo and you meant to 1/12 (12/12)? Not sure i’m understanding correctly.

If the first is right lowering the pitch would most likely increase the load and likelyhood of ice dams so that would make no sense at all

If the second is right and and the roofer needs that much pitch to have confidence in his shingling you might want to try another roofer. As long as the roof is well ventilated ice damming shouldn’t be a problem and many roofs are done that pitch in snow country with no problems.

If I’m misunderstanding and the weight of the snow is the issue either decreasing the span between rafters, larger rafter size or both would take care of the problem and still be able to maintain the pitch you want.

Sorry if I was unclear – we want the flattest roof we can get. From what we understand, 1/4 inch per foot is the best we can hope for, and we’re okay with this. Unfortunately, the roofing company won’t warranty a roof with such a minimal pitch, so the contractor wants us to increase the slope. This will change the entire look of the design, which is minimalist, modern, one-story, with a roof that appears flat. I see minimally pitched roofs in other snowy climates and can’t figure out why it’s so difficult to get a contractor and a roofing company to agree to build this for us. Just trying to figure out if what we want is impossible. We’re willing to do what it takes to make it safe so it doesn’t collapse, but don’t like the idea of an unwarrantied roof. We’re wondering if the problem is the the roofing company, which is used to building traditional homes with pitched roofs, or if any roofing company would refuse to warranty such a low pitch in a climate with heavy snow.

You can have yourself a .25/12 if you like, but it won’t get shingled. There are many flatroof methods that will work perfectly for you. Some flat roofers on here will probably chime in.

Although shingle companies warranty their materials for a 2/12 (2 inch per foot) installation, a lot of companies (the people who actually come out to fix/repair) won’t warranty it due to its low slope.

IMO you’re being unreasonable.

It’s not a good idea to have a flat roof in snow country to begin with if you don’t have to.

Don’t worry so much about the warranty, just get some Sarnifil, Fibertite, or IB installed by factory certified installers and you will be fine.

Flatpak prefabs were developed for Minnesota snowloads and all have flat roofs with warranty. There are homes with flat roofs in Norway and Colorado. My question was not whether our design was reasonable, but how to get someone to build what we want.

Thanks for the responses.

The majority of schools, offices, hospitals, etc around here have flat roofs (1 or 2% slope), and we probably get as much snow, or more, as NH.

This is a problem with the roofing contractor. There are plenty of people who will install a flat roof for you, but first you need to have your architect hire an engineer who can design your roof for snow loads in your area.

Edit: In regards to warranty, flat roofing manufacturers offer warranties if you use their complete system (Soprema, Iko, to name a few). Maybe take a look at the national Roofing Contractors Association to find some other roofers in your area who know a bit more about flat roofing. … fault.aspx

Excellent ideas – thank you!