The stuff known as "aluminum deck plate" is available in 8ft-by-4ft sheets (about 1 1/4 by 2 1/2 meters). A single sheet of farily thin stuff (but rather thicker than "tin roof" material) may cost about $80 at this writing, and perhaps less in quantity. I've been mulling over various facts about roofs for a time, and was looking for better alternative to the fairly common asphalt shingle.

The first thing to consider, about a roof, is its angle. Generally speaking, a more angled roof is found in more northerly climes, so that snow doesn't build up so thick as to collapse the building; it avalanches off first. These roofs generally have two flat angled sides that join at a central peak/edge.

Well, not so long ago I found myself in a house that had a leaky roof, and the reason it was leaking was because the peak/edge was level. The overlapping shingles along the peak didn't actually encourage rainwater to always flow to one side or the other of the roof; some water could get between and then under the shingles. Only at the peak/edge. If that edge had had a tilt, then the normal way that shingles overlap would have prevented that leak.

Currently I'm thinking about a roof that is basically flat but not level. It has no ordinary peak/edge. The highest point of the roof is one CORNER of the building. And the diagonally opposite corner of the building is where the lowest point of the roof goes. There is no reason such a roof cannot be appropriatly steep, for more northerly climes.

With this angled flat roof in mind, we start at the lowest corner. The rafter beams have all already had a layer of plywood covering them; the main roof material only needs to be added to prevent leaks.

At the lowest corner we lay down a full-size sheet of aluminum deck plating. Think of it as an extra-large shingle. It has been pre-drilled with mounting holes. We need to use aluminum-alloy screws (a very necessary elecrolytic-corrosion prevention measure), to mount them to the underlying wood. And we use silicone to fill each mounting hole before each screw is applied.

Sheet after sheet of deck plating, and in a not-too-abnormal shingling fashion, we work our way up one edge of the overall angled roof. The overlap only needs to be a few centimeters, especially if more silicone sealant is used. Also, since aluminum is a malleable metal, the last sheet, that extends past the higher edge of the roof, can have a bend-down portion, so that no rain can get under the roof at any part of the higher edges.

Back to the low edge, and lay down another wide swath of deck plating, shingling over both the latest sheets and the sheets of the first swath. Swath after swath, we work up to the other high edge of the roofline. Every sheet on this edge has a bent-over lip, of course, and the final corner piece needs two bent lips, with perhaps a brazed/filled cut between them.

In most places aluminum corrodes very slowly, if at all. I tend to think this roof should last for quite a few decades, with practically no maintenance. And the main door to the house would be on one of the higher walls, of course. Rainwater won't be flowing off so much on that side. I'll try to draw up some sketches in the not-too-distant future.
-- Vernon, Sep 22 2006

One source of deck-plate sheets http://www.diamondl...om/diamondpiece.htm
Just so you know they are readily available. [Vernon, Sep 22 2006]

Corrugated metal http://www.ondura.com/started1.htm
What's wrong with just using this? [xenzag, Sep 22 2006]

Metal Roofing Alliance: Aluminum Roofing http://www.metalroo...luminum_roofing.cfm
Or these shingles? [jutta, Sep 22 2006]

Metwood http://www.metwood.com/
Everything you need but the roof cover. [reensure, Sep 27 2006]

Large sheets catch wind very easily, you are going to have to have some pretty strong attachments. Especially since from certain wind directions, the angled roof is going to act as an airfoil.(+)
-- Galbinus_Caeli, Sep 22 2006


[Galbinus_Caeli], that depends on how much the roof-sheets extend past the walls. And since on the high side the sheets are bent over the edge, there should be less catching-of-wind than you are indicating.

[xenzag], ordinary steel rusts.

[jutta], hmmmm, never heard about those before. Thanks!
-- Vernon, Sep 23 2006


cat on a hot thin roof?
-- Zimmy, Sep 23 2006


They don't have to extend at all. An angled roof generates quite a bit of lift over its entire surface. Shingles are rigid enough to avoid lift off even though they are only nailed at the top. These sheets are probably too large for that, so they will need to be attached all around the perimeter, sealing those attachment points may be the most difficult aspect.
-- Galbinus_Caeli, Sep 23 2006


Agreed [Galbinus]; it seems to make sense that the fast-moving air above the roof will be at a lower pressure than the stationary air within the building, or is this a misinterpretation of Bernouilli?
-- david_scothern, Sep 23 2006


Sorry, I am not an areonautical engineer, so I am not sure Bernoulli is the right mechanism. But whenever you deflect an airstream you create high and low pressure points.
-- Galbinus_Caeli, Sep 23 2006


Hey, an ordinary peaked roof AS A WHOLE therefore should have the same problem. Or at least the side of the roof exposed to the wind. I think the engineering is such that that is a solved problem. Next, I know that these sheets need to be attached in more than the usual places, which is why I specified using silicone-filled holes, for the mounting hardware. Obviously such a detail isn't so necessary if you have the same amount of overlap that ordinary shingles have, but I only specified an overlap of a few centimeters.
-- Vernon, Sep 25 2006


//Hey, an ordinary peaked roof AS A WHOLE therefore should have the same problem.//

They do. Building codes (in the US) are very paticular about how your roof is attached to your house for this very reason. Here in Georgia, US, I was required to add eight inch steel straps to alternate rafters.

Watch some news footage after a hurricane. You will see a lot of relatively intact houses with no roofs.
-- Galbinus_Caeli, Sep 25 2006


I've worked on a few all-metal homes. Thanks to gypsum board, wood, tile, and paint you'd not know them from the stick and mortar house next door. The roof can be plated with flat shingles, barrel tile style plates, "Key West" style plating, or wire backing with heavy set foam slathered on.
-- reensure, Sep 27 2006



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