Old Derbigum Roof


#1

I have old derbigum roof. The angle hair is showing. Some areas the hair is blowing in the wind and when I press on it the membrane it feels brittle. The field seams are in good condition. The flashing seams are in good condition. But where the membrane makes the transition from cant strip to vertical wall the membrane is starting to split horizontal. I read some other topics but I have a hard time applying coating to old roofs. The slop is good but there are a few areas that pond and of course it’s along the drains, crickets and saddle. All coatings that I have seen peal off within two or three years. That’s with cleaning, priming and then coating.

I’m also not a big fan of recover. Never applied a foam roof, seen them after installation and it seems like there’s a lot of maintenance on the top coating.

#1 – Foam applied to a properly cleaned surface. Will it stay in place or become unattached and blister.

#2 – This roof is semi-busy. I know walk pads are good but the HVAC people never stay on them. What is the typical maintenance on the coating on the foam?

#3 – Warranty?

#4 – Two story’s – easy access – 100 sq’s

#5 – Cost per sq – Chicago area

Thanks for the input


#2

How old is the Derbigum? Is it Owens-Corning Derbigum, or Performance Roof System’s Derbigum?

Since you are talking about angel-hair, I’m going to assume it is the OC version of Derbigum where they changed the formulation and added lots of fiberglass. I suspect the ply-lines on the Derbigum if still visible are yellow? If this is true, then you are probably also getting some alligatoring of the surfacing where there is not a lot of exposure to direct sunlight, and the angel-hair where the sun cooks the roof membrane.

Alright, now tell me if I’m right, and then tell me more about the building. Do you have a metal roof deck? Roof board insulation, concrete, lightweight concrete, etc? How was the original roof attached, i.e., mechanically fastened base sheet and torched, etc.? Photos would be great. As for coatings, typically most coatings you see peeling are acrylic coatings that do not stand up to ponded water. If you are going to go with a coating, you should use a urethane coating.


#3

There is not alot of maintenance to do on the coat of a foam roof. Pressure wash and recoat every 10 yrs. The foam does not “come unattached and blister”. It will blister if applied over moisture so application by an accredited SPF crew is key.
I wouldn’t reccomend SPF in a high traffic area, you can and it may work out, I just wouldn’t reccomend it.
If you have moisture already permeating the system/substrate then coating or SPF will be tough as both require a “bone dry” surface. Neither should be applied if even the dew point is high.
Warranty depends on the thickness of the coat applied and the manufacturer used.
Price depends on specifics.
Use urethane not acrylic.
What is wrong with going back with Derbigum? It’s a fine product.


#4

[quote=“Cerberus”]How old is the Derbigum? Is it Owens-Corning Derbigum, or Performance Roof System’s Derbigum?

Since you are talking about angel-hair, I’m going to assume it is the OC version of Derbigum where they changed the formulation and added lots of fiberglass. I suspect the ply-lines on the Derbigum if still visible are yellow? If this is true, then you are probably also getting some alligatoring of the surfacing where there is not a lot of exposure to direct sunlight, and the angel-hair where the sun cooks the roof membrane.

Alright, now tell me if I’m right, and then tell me more about the building. Do you have a metal roof deck? Roof board insulation, concrete, lightweight concrete, etc? How was the original roof attached, i.e., mechanically fastened base sheet and torched, etc.? Photos would be great. As for coatings, typically most coatings you see peeling are acrylic coatings that do not stand up to ponded water. If you are going to go with a coating, you should use a urethane coating.[/quote]

Thanks Cerberus

Building is 1960’s? The owner has no idea how old the roof is or if there is a second roof.

Metal decking, did not take a core. Was not able to see ply-lines. There is alligator. The building is a school so it is heated and cooled. The roof doesn’t look bad except for the angle hair. I am getting a lot of different feed back from other guys so that’s why I am trying this site out. I read some of the other topics and they were very good and funny. Just hope I don’t get goofed on.


#5

[quote=“Krakkerjak”]There is not alot of maintenance to do on the coat of a foam roof. Pressure wash and recoat every 10 yrs. The foam does not “come unattached and blister”. It will blister if applied over moisture so application by an accredited SPF crew is key.
I wouldn’t reccomend SPF in a high traffic area, you can and it may work out, I just wouldn’t reccomend it.
If you have moisture already permeating the system/substrate then coating or SPF will be tough as both require a “bone dry” surface. Neither should be applied if even the dew point is high.
Warranty depends on the thickness of the coat applied and the manufacturer used.
Price depends on specifics.
Use urethane not acrylic.
What is wrong with going back with Derbigum? It’s a fine product.[/quote]

No, the system is great but I was just thinking that it might be cheaper to foam the roof instead of tear-off. thanks


#6

I went to the ERSystems seminar and it seemed like a good system. But then I looked at a few of their systems and that’s were I got the blistering and detachment around the drain sump and the coating was only five years old and it was badly pealing.


#7


#8


#9

I have seen the spray urethane/acrylic? on an old Derbigum. Looked pretty good, but I have no experience or working knowledge.

Try calling Rose Roofing and Sheet Metal in Chicago. Aaron checks in here sometimes and I think he knows a bit about spraying. Check out the bottom revolving banners at right


#10

poor old derbigum roof.
did mean old johnlieb not coat
you since 1978.
hang in there old girl.

mr jlieb,
please silver coat your historical
vintage derbigum roof.

gweedo.


#11

messed up.


#12

Well coating would be an option and it would probably be the cheapest option in the short term. How ever long term it would not. Coatings definatly have alot shorter life span. I have seen coatings last from anywhere from 3-10 years. In my opinion PVC roof is the way to go. PVC has a very high UV reflective % (Sarnafil Membranes are 86% UV reflectant which is the highest in the industry) The more UV rays you reflect the cooler the roof which lowers energy bills and also the burden on your energy equipment which make them last longer as well. PVC roofs will last 25yrs+ (we have roofs over 30yrs old still performing perfectly). We also can recycle 100% of or membrane after its life cycle. We have many roofs in the Chicago Area to include Chicago City Hall which is a Green (Vegitative) Roof system. Feel free to email me any questions.


#13

Where are you located John? The region you are in will likely make a difference in what to do. As for the angel-hair, if the membrane looks good otherwise, and there is no blistering, you may could get away with installing another ply of mod. bit. over the existing roof. Obviously, you are there looking at the roof and I am not, so you will have to determine whether you think it is a good candidate for a roof overlay (something I generally do not like to do). Otherwise I would go with a urethane coating as an alternative if you don’t want to tear-off. Now, if you want to replace the roof, that is a different story.


#14

john where is this bldg located. chances are i put it on. there are many solutions to this ol roof. need more info!!!


#15

I installed a lot of KMM and Derbi-Gum when they first came out around 1978 in the Chicago area too.

Ed


#16

also keep in mind the green roof ordinance in the city of chi limits. which requires you to have a white or reflective coating on all flat roofs