Insulation applied to EXTERIOR of flat roof?
 

I am looking at a house (ok, its under contract already) and I hadn't realized that it had no (or very poor) insulation under a portion of the roof that is flat. On the interior, there are lovely hardwood exposed beams. The EASY way to insulate would be to roll out nice thick insulation and put drywall up over the beams. Great for energy, bad for ruining the look I liked. For sure, I would benefit from an elastomeric paint- that would help considerably. But I wonder if a product exists that lets you insulate a flat roof from OUTSIDE (its flat but does have maybe a 5 degree pitch). Its just a thought and I am googling now but I figured maybe someone here knows something about this or has other good ideas.

I haven't done this but just an idea.
Get sheets of foam insulation, lay that on the roof, lay thin sheets of plywood, cover the plywood with asphalt shingles (or roofing grade tar paper).

Snowroof is the only thing that comes to mind

Similar discussion I started earlier. Roof Overlay - Insulation

What type of roofing material is on that flat roof ? I would tear off what is on there now , loosely nail down some 4 ' x 8 ' sheets of foam anywhere from 2 " to 3 " thick . Over that I would screw down metal roof panels . But you do have to have some roof pitch for it to work .

We had the exact same situation in our house. Nearly flat roof over the family room. Exposed beams (on the inside). Replaced the roof for the rest of the house and wanted to insulate the large living room in the center of our house.

There is a rigid insulation that our builder suggested. Something like R-30 level of insulation. But it would require some basic framing (because it's about 5 or 6" thick) to enclose on the exterior.

Or, put up drywall for the ceiling on the interior and enclose either that rigid high efficiency insulation, or put in thinner fiberglass insulation (R-19).

It was about $6K to do the exterior rigid insulation (to preserve the exposed wood ceiling), or half that to drywall and R-19 the ceiling from the inside. So we went for the cheaper option.

I think I am the only one whi notices the difference. My wife, family, neighbors, and friends haven't noticed anything different. So maybe losing the rxposed beams and ceiling height is something no one will notice.

Had it done in my flat roof hacienda style home in Albuquerque.
EX-E1 SUSTAINABLE BUILDING SYSTEMS, LLC

Roofing over Insulation a metal deck is the typical installation on commercial building. Flat and taper insulation is used everywhere.

You guys need to get out more.

Call a commercial roofer. They do it every day.

About a decade ago I got a quote from https://www.yelp.com/biz/bronnis-roofing-and-siding-ann-arbor for doing the roof of a 12,000sq condo.
About $45k then and I'm sure it would be much more today.
Probably not an accurate quote 'cause I bought him lunch but he wouldn't let me take pics.

Setup would have been triangular (to drop the water into the scuppers) custom-made hard foam sheets, covered by plywood (for strength), covered by sufficient mil (25-30?) torch-down rubber sheet up the walls, covered by the white rolled paint.

(edit: Forget the above. Just noticed your location)

I've seen spray foam used. They were able to get the right pitch so water ran off. It was covered with a rubber paint.

Here's video: https://www.youtube.com/watch?v=zIl4MhekwrA

your new place is in s fla ?
our codes are nuts
but we live in hurricane strike zone
so anything can be blown off

what is the current roof material ?

we are thinking of 3 1/2 layers of ply screwed and glued not nails
with lapping joints to become one big ply roof
wish we could just paint it but codes require blowaway shingles minimum
over tar paper nailed to the ply that will also blow off in any real hurricane
not so much for heat insulation as survival

read about local condo's that had foam roofs that failed
and I think the code outlawed that type roof

Our new build is done with insulation on the top of the deck, peel and stick membrane then Polyiso insulation then a top layer and screwed to the deck and two ply torch on membrane over that, can use metal if you have enough slope need about 1 1/2" over a foot.

Any commercial roof co will inform you of the details, not cheap though, up here about $20 sq ft if I remember right.

Yes!

I have a flat roof. Didn’t know anything about it. I had to install a few vents. I called the same company that installed the roof system. I quickly learned a lot about it. I shadowed the workers asking questions and helping.

My roof is an IB SYSTEMS. single sheet of plastic. It has a 3” thick foam board directly underneath. He told me the r-rating but I forget. It insulates awesome.

Another option may be insulate and drywall the sections between the beams.
You would lose some of the visual depth of the beams, but still have the "exposed beam" aesthetic (and no messing with the existing roofing material). YMMV...

This is exactly what I was thinking while reading through the earlier posts. You could cut sections of rigid 2" thick insulation board to go between the exposed beams on the inside. Some construction glue would hold it in place while you could bury some wide head screws to ensure it won't drop. Paint it to taste, done. I woule be leary of putting any insulation on the exterior of my house knowing how the wind, rain, snow can infiltrate anything.

When done right the spray foam with the silicone sprayed on top works well. When not done right it is a nightmare.

This was sort of my idea- I was going to roll out some thin insulation or cut boards, and then put some fairing strips in and put in a false ceiling losing half of the beam depth.

Interesting ideas so far everyone.

What I know right now is that the roof is flat with enough pitch to throw off water. It is some black stuff that looks similar to what I have on my current house, and when I put the elastomeric coating on it at my present house it cut down heat a good amount. That said, at my present house the flat portion was only over an exterior porch so I wasn't super concerned anyhow. I'm waiting on the inspection report, hope to get it today. That should have pics of the roof and hopefully tell me more about what I am dealing with up there. I will share.

RAMM.

more info. the seller of my house paid to transfer the warranty to me. she gave me the receipt for the job. IIRC, the roof was 13 months old when i took over. brand new (in roof years).

what shocked me was how inexpensive it was.

i hate flat roofs..but if i had to have one, IB roofing systems is the ticket. it is designed to handle minor ponding. mine ponds a tiny bit. i called the main headquarters and they told me the system was created as a solution to ponding roofs; on the east coast. the roof is white and it reflects a lot of heat in the summer. the hardboard insulation is really nice and quiet too.

i wont retire in this house because as an old man, i wont want to climb up there to do my twice a year sweeping. that would suck..i could break a hip! i'll install another brand new roof and sell the home..move into a condo :)