Screened in Porch - Roofing Options

[imported_gbeichho]

Hi,

I own a cottage and I am looking to build a screened in porch. The porch is going to be about 13 ' long, 15 ' wide. A couple of contractors have already a look and both of them recommended the lower cost option of continuing the current roof at a very low grade using flat roof material to prevent leaking.

I would like to investigate doing the work myself and creating a proper cathedral roof perpendicular to the main structure. I have two questions:

1) The main roof is currently metal, is it difficult to join another cathedral roof into it? I'm assuming I should make the new roof metal as well.

2) Does attaching the new roof to the old put more strain on the original roof, requiring it to be strengthened?

Thanks,

George

[Wgoodrich]

If you plan to install a pitched roof on the side of an existing roof's flat pitched surface most often you install a ridge board the entire length of the new pitch roof through the existing roof and attach that ridge board to the existing rafters on both pitch angles of the rafters. Then a stiff leg is installed to assist in supporting that ridge board is accepted practice running down to a bearing wall. However a true properly installed dormer would stand on its own not requiring that stiff leg.

To join the two opposite running ridge boards you will create a valley on each side of the new pitched roof where the new roof meets the old roof.

If you old roof has metal roofing then I would match that existing roof style on the new pitched roof if it were me. The valley in this case probably will be a metal valley material that is layed under both existing and new roof with both roof sides overlapping over the metal valley.

Not hard to do but many will try to talk you into a flat dormer style roof to make it easier on them. Looks and life expectancy would support your pitched roof thoughts.

If you go the dormer roof and the pitch is less than 2 / 12 pitch then code requries roll roofing or rubber roof. I suggest rubber roof if you must go a flat dormer style roof with 2/12 pitch or less.

Good Luck

Wg