Gravel roof, two layers, remove to replace?

I have a gravel roof, needs replacement, has two layers already.

  1. do I need to have the old layers removed, which will probably require new decking?
  2. is a product like Firestone 160 or 170 a cost effective replacement?
  3. does a 160 or 170 product require removal of all roofing?
  4. is there another less costly alternative to tar & gravel?

Thank you in advance for your response.

David DuVall
Western Kansas

Being a ‘steep’ roofer, I’m not sure about either system you’re mentioning, but I do know you have to remove the existing roofs.

Tar & Gravel has alot of weight to it & you allready have two layers. You could put a lightweight roof over it by shoveling off the loose stone, plate & screw down a light recovery board 1/2 inch - 1 inch making sure all screws are long enough to grab the deck/substraight, & glue down .045 e.p.d.m. rubber, .045 p.v.c., or .045 t.p.o. Thats just a couple options, but if you plan on keeping the property you might as well remove & replace the whole roof system. You yourself said it might need deck replacement, so you might as well remove it all the way down to the original deck and find out. You ever seen a luggage rack on a hurst? Me either, can`t take that money with ya. :wink:

Tinner, he is talking about Firestone 160 or 170 which is rubberized capsheet, which comes in a 1 square roll and weighs 90-100 lbs. each. I dont recall the # codes for 160 & 170 i think one is smooth surface & the other is granulated or one is mop down & the other is torch down, something like that.

Thanks Corey. Add in a base and mid ply and you’re around 250#, give or take.

Modified bitimen was the word i was looking for, for that Firestone product but my wife was in my other damn ear so i couldn`t think of it at the time.

Remove and replace allows you to see the condition of the deck, and makes life easier 20 years down the road when you are trying to find some sort of crazy leak. Also, the weight issue.

Here in Ca. we are required to remove down to the wood sheathing if there are two layers. The only benefit to leaving an old roof layer is the tear off cost. The bad benefits are Extra weight on your home, covering dryrot that will just keep on rotting, heating the new roof to higher temps inturn causing premature failure. Thats why we always tearoff no overlays not worth it.

Building code requires you remove the old stuff. Maximum of two layers are permitted, no exceptions.

Donl, is that code nationwide? or is there exceptions? I have tore off roofs on old mill buildings with wooden decks here in Massachusetts with 9 seperate roofs on them, friggin14 inch screws & shit. When you have to remove 2 or three epdm roofs to get at the remaining pitch tar & gravel roofs. When you have to rip 1 t&g and run the cutter thru again & rip another, like peeling an onion. We all know it should only be two layers but sometimes they cant afford a rip, or limited access. What if this guys place was built during the cold war & the roof deck is a 16 inch concrete pour? We know its not but hypathetically, a 16 inch pour cant take another layer & then some. Ive been on them in Worcester with Bobcats ripping pitch, just piling it up like snow removal guys do while i wait on the next dumpster.

I’ve seen a third layer installed on a couple of occasions but the building was pretty solid and it required engineering work to be completed and submitted. Also if the layers will come apart easy enough I have seen removal of one layer only followed by an overlay. Like previously stated though, dry rot is a killer and if you suspect any it is better to tear off down to the deck and get the job done properly.

Like corry I have come across roofs with way more than the normally allowed two roofs but they were all oddball type projects and were more than likely done without permits.