TPO or torch down 2 ply modified bitumen

Hi to all experts

I have a 20,000 sq ft flat roof. Current roof is built up modified bitumen ( did I describe that correctly?)
It is black and uncoated.
We have several leaks and called roofers down for quotes.
Most want to rip it out and start over and charge more than 6 figures. I do not have the money for it. No can do.

I have 2 roofers coming in at about $50,000.
One is offering TPO mechanical installation. This will be applied over the existing roof. 15 to 20 year guarantee
Second is offering to install steel plates over all airbubbles. And 2 ply bitumen which will be torched down and also applied over existing roof. 15 to 20 year guarantee

2 other quotes for repair and patch the leaking areas. There are 13 spots which leak. And then coat the entire roof.
These prices were $15,000 and $22,000.
No warrantee on $15,000 quote
5 year warrantee on $22,000 quote.

Can anyone offer opinions? Which type roof is a better system?


If going over a built up asphalt roof and tear off not an option I would personally go for torch down modified bit. Are they putting down 2 ply of modified, or a mechanically fastened base sheet and one ply? If they are putting 2 ply of modified directly on top of build-up that would be a good roof.

I am assuming the tpo quote includes mechanically fastened recovery board or insulation board?. If not putting tpo directly on top of an asphalt based roof would not be a good mix.

Thanks mpa for your response.
I cannot afford a teardown. Wish I had the funds.

The current top layer of roof is smooth surface modified bitumen roof system.

The quote for The modified bitumen will be a two ply. Black on bottom and white on top.

The quote for TPO does not mention an under layment, but they verbally said they would level any deeper pits or ridges. And I should expect to remain with some wrinkling.

Does this change your opinion or are you still in favor of the modified

Thank you

We commonly do double ply modified, smooth on the bottom granular cap sheet on top, installed right it’s pretty bullet proof and maintenance free. We normally tear everything off, vented base sheet and two plys, but in my opinion a Build up or un-coated modified, like you have, is better than the cheap fiberglass base sheet a lot of guys use.


Which location do you service?

Philadelphia area. Back to your original post, the coating proposals, is that silicone coating? Wouldn’t recommend coating a leaking roof, espically for 15k no warranty. Coatings are great to extend the service life of a good roof, not fix failed ones.

The $15,000 quote is for aluminum asphalt coating. Including patching all areas we assume are leaking or are obviously leaking and use torch to remove areas of oxidation.
It says labor is 15 years warrantee and the roof should be recoated in 5 years. It includes a warning not to use at silicone coatings.
Reason I said no warrantee is because these guys would be traveling 8 hours. I doubt they’d come back for a small problem

How old is the roof? Aluminum coating does nothing in the way of water proofing. The purpose of aluminum coating is to reflect UV rays and prevent them from breaking down the roofing material, extending its life. If the roof is already falling aluminum coating is likely a waste of money.

I do not know how old the roof is. Estimates are telling me 10 to 12 years.
Yeah, I realize the coating is an attempt to extend the life of roof before it fails completely.
To the inexperienced eye, roof looks ok. Few areas of air bubbles, 4 areas around drain no good. One area softened with water, feels mushy. But vast majority of roof looks clean.
$15k is still a lot if money so not sure if this is money well spent.
We are in southern VA off the I-95

2nd Coating quote for $22K

Leaks area repairs using APP modified bitumen roof membrane
Roof surface coated with RM Lucas 648 non fibrated Aluminum roof coating at rate
of ½ gallon per 100 sq. ft.
5 year warranty

1st off you need to determine if your roof is even a candidate to install another roof over top ,has any contractor given your roof a "Thermal Scan " ? The scan shows all areas where insulation is wet and MUST be addressed before installing a recover,if you don’t tear out the wet insulation and repair rotten decking/insulation the moisture trapped under your new roof can cause a hell of a lot of problems ,2nd is this ,have you contacted a reputable Roofing Inspection service ? A 2,000 square roof should have its instalation monitored by an inspector daily ,the costs aren’t that high and it garanteed you do not end up with a fly by night roofing system ,I can almost promise you the company who gave you an estimate of $22,000 for 2,000 square is planning on cutting every corner possible and using the cheapest materials available ,a proper 2 ply torch down modified recover consists of a modified asphalt base sheet to be torched or screwed over the existing roofing with its seams welded ,then a full ply of a quality cap sheet ,any material/product they sell you for your top layer that costs less than $150 a roll is garbage .

If for $22,000 the contractor plans on removing and replacing all wet insulation ,installing all new pitch pans ,pipe leads ,roof drains ,wall flashings with termination bar while using premium quality materials ,and is willing to have their job draws go thru a roof inspection service quality assurance then by all means the 2 ply torch down modified system is the better choice ,one things for sure ,no reputable roofing contractor covers blisters with metal sheets and roofs over them .

Thank you Detroit journeyman
Sorry if I was unclear. Roof is about 20,000 sq ft

I’ve got three options
1.Tear down full roof and replace. Quotes ranged from over $100,000 to $250,000. I do not have money to pay for this so it is not an option.
2. Leave roof and use torch down 2 ply modified bitumen with metal plating over air bubbles for about $50,000
Another roofer quote leave roof and cover with TPO mechanical installation with no underlayment for about $50,000.

  1. Buy some extra life for the roof
    One roofer quoted to repair 13 leaks and coat with aluminum paint for $15k
    2nd roofer quoted to repair 13 leaks and coat aluminum for $22k

Roof is wet through. 2 roofers took core samples. They both said to tear out.
Other roofers said wet is no problem, it will dry out.
Everyone swears their way is correct and everyone else is wrong

What type of decking is under the existing roof. If it is saturated and water is trapped under the existing roof it will not dry out. 20,000 sq ft is 200 sq not 2000.

Roof has 4 sections.
1 section has steel decking. This is best condition and not tested for water
1 section wood deck, tested and core sample is wet
2 narrower sections wood deck and gravel and asphalt below the modified bitumen system. Tested and core sample is wet

2 roofers swear will not dry and want to tear out full roof.
2 roofers swear other two are lying and trying to make more money and roof will dry without a problem

The more accurately you describe your situation the more it sounds like going over the existing roof is not a good option.

Any time you have moisture trapped between multiple layors of roofing and add another layor on top the water will become permanently trapped. You Want to get core samples of all sections. Roofing is not applied directly to steel deck there is either insulation board or some other substrate installed to the steel deck.

The best advice I can give you is get a full inspection report of the roof done by a 3rd party before considering any proposals from roofers.

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The guys who are trying to make more money are the guys who want to go over the existing roof or just coat it. Tearing it off is the right job. Going over the existing for 50k is about 1/4 the labor of tearing it off for 100k.

Your best bet might be to just patch the leaks to get another few years until you can secure the financing to do the right job. Dont waste money on coating a failed roof. Whoever is offering 15 and 20 year warranty on going over a roof with water trapped under it is full of shit. The deck of will be rotted out before there warranty is up.

Modified has around a 12 year warranty. If it is not coated, expect less. If the roof is already 10 years old and somebody is saying they can patch it and put some aluminum coating on and give you a warranty…that is just crazy.

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