Upgrading a Flat Tar-and-Gravel Roof?

Sooo ... our current house has an old school tar and gravel roof. It's a 1975 build, and IMO not as well insulated as it should be. Annoyingly, there is no access to the insulation sandwich for upgrades; it has to happen over top of the existing membrane.

I would prefer to avoid another tar application. We pull a lot of rainwater off the roof for our plants. It would take years to cook out the volatiles off a new tar roof.

I have heard of spray polyurethane as an option to reseal the roof and add some insulation value. Apparently it meets LEEDS specs.

Thoughts?

Why not lay battens across the existing roof, fill the space between the battens with insulation and sarking and fit a metal roof on top.
Advantages;
- get new roof you can drink water from
- up
- you will be able to hear the rain!date insulation
- make your house look beautiful

Yes, I thought about converting the roof to a conventional one. If it was a simple roof, that's what I would do. It's a split level roof, though, with all sorts of complicated bits. I don't think I can afford such a major undertaking.

Douglas, what is your annual rainfall?

Can you send us a photo?
Flashing is something you could do I am sure.

Rubber or Vinyl roof membrane can be applied over the tar after you scrape as much gravel off as possible and lay down foam or bubble wrap. We use Mylar coated bubble wrap with the metal roofs and I have done at least one former hot mop and gravel roof. The foam acts as a cushion so the rubber or vinyl doesn't get punctured.

Oh and also its much safer (especially the vinyl) for water usage.

John F Dean wrote:Douglas, what is your annual rainfall?

Maybe 18 inches annually, on a long term average. Much more last year, much less this year. It's a fairly dry aspen parkland climate, but far from a desert.

I should add that this is not a DIY job. It will be hired out, as soon as I can figure out an option that's less nasty and somewhat affordable.

I do have other sources for plant water, though it's a pain. But it's do-able.

And if you're wondering how I ended up in a house with a flat roof in the first place, the answer is "It's Complicated." Sigh.

Edit: If this was our forever house, I would dig deeper and rework the roof entirely. In 5 years, maybe 10, we may not be here.

I want to thank everyone for their thoughts and ideas.

As you can see I continue to puzzle over alternative approaches that are reasonably affordable, add insulation, and preferably don't stink up my rainwater. We'll get some contractors and quotes, and see what can be done.

Thanks for lending me your ears.  

Given the rainfall, the flat roof doesn’t strike me as that bad if an idea.  My problem is that I can’t come up with a better solution than more tar.  Once I did check into the use of a “rubber” membrane, but the cost vs life expectancy made it undoable.  Besides, there would still be a question of potential toxins.

Thanks for posting this thread, Douglas. Since you asked for "upgrades," maybe consider DIY skylights on the problem spots of your existing roof instead of redoing the whole roof. I installed our fourth skylight and it was not outrageously difficult. The varieties of skylights are vast: small to large, clear and opaque, angled risers so you can direct the light toward the right place in the room, and various kits. They freshen up spaces tremendously giving much needed light, creating lovely tapping with the rain, and cloud movement casts lively shadows in the house. You can insulate the area around the skylight when you create the opening. I really like the play of the light. As the roof deteriorates, I will keep adding these "light patches" to extend the life of the roof and upgrade the living space.