Aluminum Deck Plate Roofing

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.