Insulating a flat roof residential


#1

I AM A CONTRACTOR IN MISSOURI AND I’M BIDDING ON A ROOF
THAT IS FLAT, THE THING IS THAT THE HOME OWNER IS GOING TO REMOVE THE INTERIOR CEILING AND EXSPOSE THE WOOD IN THE ATTIC AND SHE WANTS ME TO INSULATE THE FLAT ROOF BEFORE I LAY THE MODIFIED BIT ROOF I HAVE DONE PLENTY OF MOD ROOFS BUT HAD NEVER HAD TO INSULATE THEM, IF ANYONE HAS ANY SUGGESTION I WOULD APPRECIATE THEM,I WAS THINKING OF PUTTING A LAYER OF POLYCOT, THEN MAYBE A LAYER OF 1/2 INCH RIGID BOARD THE POLY, HAD A R VALUE OF 14 AND RIGID HAD SOMETHING LIKE 5 OR 6 NOT SURE ANY THOUGHTS WOULD BE HELP FUL :?:


#2

Please use LOWER CASE

Well, rigid board or ISO has a 6-r per inch, so 1/2 inch will have like 3-r value
Never heard of polycot. Can you put insulation between the rafters?


#3

sorry (new here) the product is not called poly my mistake it is called prodex it is a foil foam poly product,and as far as insulating the rafters she wants to leave them open kind of like a cathedral ceiling why i don’t know,i know they use the prodex for metal buildings, and have even used under shingles, but just not sure about a flat roof
i was thinking put layer prodex and two layers rigid ?


#4

If I am understanding you right…then you want to insulate the rooftop with some kind of ISO board and torch over that.


#5

You can install a Modbit system over most any kind of roofing insulation although I wouldn’t recommend any type of wood fiber.If torching then the base sheet installation is critical. Theres many different systems like cold applied, self adhesive and mopped in that can go over Iso insulation thats fastened to the deck.


#6

thanks guys appreciate suggestions have been very helpful


#7

It sounds like you may be a little over your head on this one. Think long and hard before committing to putting on a roof that you have no experience with.

Your insurance is up to date, right?


#8

The easiest way for you to get yourself in trouble, warranty and financial wise, is to install a product and system that you have now experience in dealing with.

Since you have NEVER installed a modified bitumen roof membrane over any rigid insulation board, this shows a very limited range of previous experience. With the home owner being the specifier, you are just asking for a whole bunch of problems to follow you around after you get involved in this project.

Ed