2006-08-09 06:44:15 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
Its referred to as ballast, most of the above is true. It protects the roof membrane from damage by the sun. But its primary purpose is just to hold the roof membrane down.
Its going out of style and few new buildings are installed with gravel ballast.
2006-08-09 06:53:52 · answer #1 · answered by Roadkill 6 · 0⤊ 0⤋
Roofing materials must be fireproof to prevent the spread of conflagrations cause by wind-blown embers. Entire cities used to burn down (Chicago, Boston, etc.) Roofing shingles employ a coating of sand to keep fire brands from igniting the tar or asphalt in the shingles. Pebbles on a roof waterproofed using tar and asphalt papers would serve the same purpose and on flat roofs would even allow foot traffic.
2006-08-10 09:14:02 · answer #2 · answered by Kes 7 · 1⤊ 0⤋
Buildings with flat roofs have a thick layer of asphalt or tar on them to seal against the rain. Rain hits with a bit of force in a downpour, so the aggregate (gravel) is the to absorb the shock of the rain hitting the roof, so it doesn't divot the tar.
2006-08-09 13:52:32 · answer #3 · answered by jogimo2 3 · 0⤊ 0⤋
They have a rubber membrane roof that is easily damaged. The pebbles serve to protect the membrane.
2006-08-09 13:50:19 · answer #4 · answered by Oh Boy! 5 · 0⤊ 1⤋
That would be a tarred roof with pea gravel applied to strengthen the surface and prevent the tar from running.
2006-08-09 13:51:59 · answer #5 · answered by Anonymous · 1⤊ 0⤋
thats stone 2 cover the tar they put down first
2006-08-09 13:50:09 · answer #6 · answered by Harold T 5 · 0⤊ 0⤋
those are martian pebbles
2006-08-09 19:09:50 · answer #7 · answered by ronw 4 · 0⤊ 0⤋