Pond roof?

I have been called about a pre-listing insp. They have informed me they have a pond roof (The roof is 2x12 8"o.c. and holds 4" of water at all times with a float and water source). Has anyone heard of them or know where I can get some info???:shock:

Yes I have heard of them various times .
Have never seen one and most of what I have read is usually a little strange and sone ones Ideas.
I do not think I would build one but willing to learn.


Would love to hear how you make out.


I believe that an IRMA roof, Inverted Roof Membrane Assembly, was intentionally designed to hold water rather than to shed water.

There was a discussion on JLConline dot com about two months ago about a similar topic.

I looked up Inverted Roof Membrane and found this pdf file so here is the link if you think it will help you.



IRMA roofs simply have the insulation applied outside of (above) the roofing membrane rather than under it. They are never intended to retain water. The reason for the inverted construction is to protect the roofing from UV rays and to also protect it against major temperature variations.

You guys are bringing back old memories about what I always called the upsidedown roof system. BUR.

Steel deck on the structural steel and then a 5/8" gypsum board applied to mop down a 3-5 ply system and then a complete mop over the whole membrane. Then the insulation was applied and held down with 10# of stone ballast. This was usually river washed stone that was available at the time.
That was banned in the late 70’s, for the impact enviroment it created on the rivers.

Wicked poor system. Saw it installed in the early 70’s and never again.
Any leak in the system was impossible to find and the steel structure had to be designed to hold that ballast system.

Never seen it again in this area.

Marcel :slight_smile:

I knew I remembered reading about this type of roof before over at the JLConline.com/forums



The Building Envelope Forum that you found is a free e-zine run by a retired building scientist, Jacques Rousseau, formerly of Canada Housing and Mortgage Corp. It comes out 4 times per year and has some of the best Canadian building scientists, architects, etc contributing. Would definitely interest you but note that some like Rick Quirouette (a lifetime building scientist) think like me about roofing moisture problems.

The archives are found here:

You’ll have to read this one- “The Anatomy of an Ice Dam”:


A paper about a study regarding pond roofs from 1984 or so.