Torching down over tar gravel roof that is smooth


#1

I have just removed all the gravel from my tar and gravel flat roof with a spud bar. The roof has been hot mopped with 3 layers from what I was told by roof contractors. I called for a few estimates. Some of the roofing contractors said the roof is in very good shape. 2 of the contractors said they would like to torch down some bitumen right to the roof, meaning they will torch down right over the 3-ply fiberglass. both said this was the best way. Does this sound correct to you pro’s. This concerns me a bit. Not the torching , but torching right to the fiberglass. I never seen this done before. but then again Im an electrician and do very little with roofs. I always thought you would have to lay a new base fiberglass sheet that’s fastened to the roof with roofing screws and plates. I was also told not to worry about the torch down because the roof is 3 ply fiberglass already. You pro’s have any thoughts on this. I was going to cold process the roof myself, but for the prices I was given I know torching is better. I did require the contractor to post a person for fire watch for a least 4 hours after the main crew is gone. Because I might not be there when they leave the job site. It’s My house.

The prices were very good, I think. since I did all the gravel removal and made the surface very smooth and power washed it with soap and water.

1st estimate. 4,800 . 2nd estimate. 5,200

both estimates include the works, flashes etc. job time 2- to 3 days.

one roofing contractor said tear it up. Put some poly-iso down with edpm. For 23k Im not a big fan of edmp… Another wanted to install foam and keep the roof. For 17k and some change. Not a big fan of that either.


#2

you can scratch it then torch down right over it.

RooferJim


#3

Tar catches on fire like its nobodys business. Personaly I’d refuse to torch over it.


#4

are they going to be priming the 3 ply asphalt roof with asphalt primer??what will the metal edge details be? is your contractor an approved installer of the material he has proposed to install?is he insured,bonded,licensed?
epdm is an awesome system also.when it is installed correctly.
how big is this roof anyway??


#5

I would not torch directly to the old roof because any defects ( splits, blisters, etc,) that develop in the old will telegraph and manifest throughout the new.

I think you wasted your time spudding, but now that it is done, I would pour down a base (a board is better with a solid mopped base) and torch to it with proper terminations to ensure you dont lose your roof.


#6

RoofBoss it’s 1500 square feet. 1/4-12 . One of the torch contractors said that they would add the roof primer for an extra $ 500.00 . Tar monkey said old tar burn like hell. I have not gone into detail with the metal work yet with him. I did require every bidder to put it in writing along with a copy of there bonding and insurance to include licence. Some roofers here in NM just have bonding and lic. I would require that they have additional fire insurance. My insurance company told me today. “Make sure they have fire insuranceâ€Â


#7

AaronB. has a good point. done all this work already.
just wondering if the surface could be primed. then put down dens deck with a torch over right onto the dens deck. this might save me some money.

I could insulate the bottom of the deck form the inside. I do have all the ceilings and walls down and have not closed them up yet, but need to soon. for my final.


#8

If I decide to go to a Cold App SBS granular system. What would be a good cold app product that binds well. that henry stuff at home depot I will not touch. I got a lot of call backs on the electrical jobs where it just began to unbind.
I tell the home owners to get a roofer now after I install the masts going through the roof I eve get them to get the hols in the roof before the job.

I take it cold application have got better Since CA and NY have done away with some torching and hot mopping.

If I do the cold App SBS. do I still need to prime the roof. and put down fiber sheets for the SBS . I read some gaf install sheets and according to them, nail in the fiber sheets. is there another way. or does the SBS system need a base sheet at all. Since I have a smooth surface.

Torching is beginning to scare me a little.


#9

Better yet, have an insulated foam roof installed with a polyurea topcoat by a ROOFING foamer with many many references. This will save you a ton of money and even pay you back. It could be a lifetime roof with proper application and maintenance.

Do NOT let an insulator foamer do the roofing, though. They just do not know the intricacies of roofing. MAny bad foam roofs were installed in the Chicago area by insulators that thought it was easy money…“just spray and pay” mentality.

Ask roofboss. :slight_smile:


#10

Also, if you install a MF Densdeck, there is no need to prime the existing.


#11

AaronB.thanks for the great advice, have a great week.


#12

Roofboss, correct me if Im wrong, but I believe DensdeckPrime can be torched right to, also Duraboard.


#13

yes my liege it can!!!


#14

[quote=“stevenje98”]If I decide to go to a Cold App SBS granular system. What would be a good cold app product that binds well. that henry stuff at home depot I will not touch. I got a lot of call backs on the electrical jobs where it just began to unbind.
I tell the home owners to get a roofer now after I install the masts going through the roof I eve get them to get the hols in the roof before the job.

I take it cold application have got better Since CA and NY have done away with some torching and hot mopping.

If I do the cold App SBS. do I still need to prime the roof. and put down fiber sheets for the SBS . I read some gaf install sheets and according to them, nail in the fiber sheets. is there another way. or does the SBS system need a base sheet at all. Since I have a smooth surface.

Torching is beginning to scare me a little.[/quote]

First of all, is your existing roof asphalt or coal-tar pitch?

If it is asphalt, then between the torch and cold-applied I would recommend the cold-applied but with torched laps. As far as priming for the cold-applied, yes you should prime the existing roof, but it need only be a light priming if the roof has been swept and is fairly clean. You can accomplish putting a light coat of primer down by spray from a pump canister. If you opt to use roller knaps, you may put the primer down too thick, which will start to dissolve the asphalt.

Another option would be to install a base sheet overtop the existing roof, and then installing a new membrane to the base sheet. If your existing roof has insulation, you will likely want to use a venting base sheet.

Naturally, the best solution is to always remove the existing roof and start anew; however, I realize that this isn’t always financially feasible for everyone.

Anyway, if you provide more information, I can provide more help.


#15

We have done quite a bit of roof maintainance and repairs by scratching an area and torching a ply right over it. In the past we have reroofed several jobs that way, never a problem. Although in the past ten years we have gone almost 100% single ply for the commercial roofing division. Better way to go in most cases.

RooferJim