We are in the process of shopping for a new roof. We currently have a tar and gravel roof which seems to be hard to maintain as our neighbors have huge eucalyptus trees that shed on our roof. Each time we go up to clean it, the gravel that was put on to protect it gets swept away thus exposing the tar to the rays.... Because of this, we were looking at what other roofing options were available. We have a flat roof and live in S.F. Do you know anything about the Sprayed Polyurethane Foam (SPF) roofs that being sold? I just had a rep. come out and give us an estimate. The cost appears to be cheaper than a tar and gravel roof and comes with a 10 year warantee. Can you enlighten us on this new type of roofing material? Thanks.