Weird Roof - with Pics!

[Dmitri L.]

Hi BP nation! 

Would like to ask for some advice on a deal in the works - 12 unit multi-family in the Tokyo area in Japan.

The building is a reinforced concrete (RC) structure, which is common here due to earthquake codes. What is a bit strange, and I hadn't seen until now, is the roof. Instead of the more typical flat concrete roof with waterproofing sealant, this one is built with concrete slab laid on a slight incline, with what look like asphalt/composite shingles over top, and the shingles painted over with a waterproof coating!

Pictures attached (Right click -> view image; for a larger version). Note the flat concrete roofs on some of the buildings in the background, which are alot more typical in Japan. Also the building right next door with a very similar roof construction - newly replaced. The age of both buildings is similar, so I suppose that should tell me something :)

The seller will "redo" the roof as part of the deal, but that really just means re-apply the waterproof coating. Existing shingles stay in place as-is. I think it's mostly a way for them to cover their a$5 (seller must warranty some items such as roof leaks and plumbing for 2 years after sale, by law), and I'm not sure that it really meaningfully extends the life of the roof. (The whole exercise costs around $3k USD).

Just wondering if anyone might have come across this type of roof, and could comment on what I should expect from it in the future. It does seem to physically be in decent shape besides some flashing which will be spot fixed as well. It does look like the shingles are absorbing some moisture around the seams..

Not super worried about the replacement cost if it's needed in the future, since the total area is under 2000sqft on a building that grosses $130k/yr. (The aging hydraulic elevator is a much bigger concern... but that's a different story!) 

But if anyone has any experience or tips, would greatly appreciate it!

Cheers

-Dmitri

[Jassem A.]

I wouldn't think it would be a problem. If the roof is made of concrete I don't think it would decay as easily as wood no matter what you decide to put over top of it.