Flat roof question (im not a roofer so bare with me)

I amb a pressure cleaning contractor in montana(17 yrs in florida so not sure if this is how its done here). I need to find out if this is typical for flat roofs in the north west.

*gas lines propped up by blocks of wood (6x6 treated lumber) when i went to move them, roofing and underlament pulled off with the blocks. (only tried one block but it looks like the roof ( which was put on last summer i was told)has stuck or in some places applied with the blocks left where they were.

*the highest point of the roof are the drains. after a rain there is lake up there a day later, in some places 2 inches deep.

*in some places where the roofing is wrinkled, i can grab it with my fingers and literal pull it off.

The customer is having problems with this commercial building leaking in two different rental areas. the roofer says theres nothing he can do until warmer weather. I am going to meet with him tomorrow and show him the areas im concerned about.
Id like to understand a little more about how flat roofs are supposed to be put together. nearly all the roofs i’ve worked on in florida were rubber or covered in pvc sheeting. i’ve never seen a tar flat room like this.
anyone herehave any experience with this type of roof that can explain to me how its suppose to look. if these huge puddles are normal,andif the material is suppose to be this fragile?

I should also mention that all the commercial buildings i’ve seen, their gas lines were propped up by aluminum brackets, or at the least pvc. i’ve never seen wooden blocks stuck to the roof like this.

The blocks would probably be ok if there was a slip sheet between it and the roof to protect the roof from movement or the block sticking to it. sounds like poor quality to me. They probably went over the old roof.

how many layers are typicaly on a roof like this. the rubber bladder style ones i typicaly clean seemed very thick, this one is literaly 1/8 thick and thinner in some places.

also what makes up a roof like this? is it just tar and paper? or is there polyester sheeting or … it looks like just tar with a reflective silver spray applied over it.

that silver stuff is just like a sealant that ive seen in 5gallon cans -its not much thicker than paint after you mix it -bufore you mix it its like a muddy alumunum sludge in the bottom of the can and like a brown liquid thick as water- gotta mix the shit out of it. but from what i know its just a cheap fix for an existing flat roof- i dont really do flat roofs

If we are talking about the same “silver stuff” it is not a sealant but a reflective coating to protect from uv rays.

could be-- i only used it once like 8-9 years ago and i was working for someone else and was just told take this up the ladder and spread it around with a brush–more like a fat pushbroom- i just went up and did the job never stopped to read the can -haha- like i said i dont really do any flatroofs im just pretty sure the thin stuff this guy saw on the roof was that stuff i mentioned

Correct John.

Now, for the other questions:

It "Probably is a Built Up Roof, meaning that it is composed of multiple moppings of Hot Asphalt and layers of organic or fiberglass felt paper.

A careful look at the ply lines on the surface would reveal how many plies thick the uppermost roof is, since I do not know if this is original or a re-roof over the top of an existing previous flat roof system.

If the drains are higher than the remainder of the roof, that is a Major cause for concern. Ponded water, which means it remains from up to 48-72 hours after the most recent rain fall, will cause severe and premature degradation of the surface asphalt coating and then the plies of felts after that.

Little lifts in the seams that were mopped together can cause almost instantaneous migration of water into the inner plies of felt, due to there being no contact adhesion from asphalt to felt papers in these void areas.

Flashings around curbs and parapet walls are a constant source of potential leaks, either from age and degradation or faulty workmanship and fastening and securing to the structure.

A very general analysis, without seeing the conditions first hand, would be that either the drains need to be located and lowered down and then patched in properly, which is always going to be the most abused portion of the roof, since all of the entire roof systems water drainage will eventually lead towards the roof drains, so the repair technicians must be very knowledgeable about how to do their tasks properly, or else it will once again be doomed for failure.

Depending on how many roof layers are already in place, a better repair, would be an entire re-roofing of the system, but also include the installation of pre-designed saddles and crickets, to efficiently divert the flowage of water to the roof drains.

As long as the drains are higher than the remainder of the roof, there will be problems, which will get worse as time goes on. So, the addition of a certain height of insulation or recovery board needs to be considered when specifying the new system.

Some single ply membranes do not exclude ponding water from their warranty provisions, but it is still good roofing practice to build and install correctly, following an intelligent feasible design and set of specifications.


I am guessing that he is describing a Modified roof.

I used to see this A LOT on flats in Colorado. There is some predisposition to wood blocks and I never understood their use. We were on these roofs to repair them by the way. Usually the poor install included placing the wood blocks on while the surfaces were still malleable or the heat later resulted in the wood adhering with the surfaces underneath. See ED THE ROOFER"S post for an explanation of the roofing application and material. I also used to see this with the “torch down” roofs (a small step up from hot mops). I also saw an inclination for the use of these blocks without slip sheets to collect and hold water, break down prematurely due to the water. The roofs we used had slip sheets and the use of any number/type of metal brackets.

what is the roof? tpo, pvc, epdm, torch, flintlastic, or hot tar, if the roof was done last year the owner should know. the silver product is probably karnack 298 wich is a uv protectent and works really well. As far as the wood this is not a roofer it is either a HVAC or a plumber. We roof them the set them. Drains are defiantly to high this is a problem. No offense guys but I don’t even know what most of you are talking about in you answers especial bmcroofer and I know you guys don’t do flats. :roll: Go ed you out of Boise?

No, I am out of the NW Suburbs of Chicago.

I felt it was a built up roof, from the sticky description he gave from the support blocks.

I am confused though, when he commented about being able to pick up the material by hand. What was it’s texture?

I haven’t read through all of the recent replies, but has the OP ever bothered to get back on and add more information?

I’ll check, but if he isn’t going to bother, either will I.


I appreciate the commentary GNFR, but if you were to read the post, you would see the mention of COLORADO- which last time I checked, wasn’t in IDAHO- which is where I am now. :wink:
As for what we do or dont do , we DO repair the flats when requested here in IDAHO. My commentary was from my personal background in COLORADO with flat roofs among others.
I hope the use of CAPS cleared up any assumptions/misconceptions about my current responsibilities vs. my past experience.

If you wish to learn more about my resume so you can authoratatively make statements about my experience, stop in the store (I am sure you know where it is), and talk to me. I would probably enjoy it. How’s St Anthony by the way amd what company do you work for or represent/own?

Pls feel free to comment on the specifics of my inaccuracies, and allow me to explain them. YOu can also PM me. I certainly dont wish to mislead anyone or be ill informed.

P.S. If the HVAC and plumbers are responsible for ALL the wood being placed on roofs, perhaps you could explain a reroof situation where the ROOFER is responsible for the re- installment of the brackets while the pipes are functional.
Like you, I dont know the history of the roof or the membrane type used.