Lightweight Over Plywood Deck?

My client has approached me regarding a re-roof project involving a wood deck. He has said that another contractor is suggesting a tapered system over lightweight and wood deck.
I personally have never heard of such a system…nor have I found any NOAs.
Has anybody ever come accross this before or know of any NOAs??
My engineer said even if there was such an NOA, he would never reccomened it.

I’d appreciate any thoughts on this.



i dont know why you would need lightweight over the plywood??..i have done many jobs with a tapersystem right over plywood or with a good pitch just a base sheet or dense deck over plywood with internal drains or to a gutter…the building will be insulated from the inside so you dont need an r value…plus with lightweight you would have to pre drill holes and get special screws and plates to hold down the tapersystem…time consuming…

I appreciate the response…
I agree with everything you have said, but for some reason my client has got this system in his head from another contractor that is also bidding the job.
I want to tell him that there are no NOAs for such a system, but I can’t be 100% sure of that( I just simply would never recommened it). That is the reason I thought I would throw it out there, just in case someone here has come across a similar system.

I have never heard of such a system and to me it does not make much sense.
What purpose is the lightweight concrete supposed to serve?
As justinconstruction07 pointed out it just creates more work and material expense.

I’m told now by the client that he actually meant to say that it would be tapered lightweight and not light weight with a tapered insulation.

either way i think the lightweight is a bad idea. What is he gonna base sheet right over the light weight?.i guarentee theres gonna be leaks from the screws popping up through whatever he goes over the lightweight with.The screws always manage to pop up with light weight.A tapered insulation system is the right thing to do.This other guy sounds like a hack.

Lightweight concrete tapered systems are phenomenal. Use a fleecebacked single ply adhered directly over them. A good lightweight applicator can guarantee drainage with any kind of on-roof equipment.

I would question putting that much weight over a plywood deck. Usually, that is best over a concrete or steel deck.

That makes much more sense.

its never a bad idea to try to get your flat roof tapered a bit.

if that helps any.