The person who used a sealant on a Duro-Last membrane did not perform to the manufacturers specifications, because all seams and patches either come pre-dielectrically welded together from the factory, or are fused together molecularly with a hot air welding gun.

A larger patch should be installed over that area after the membrane is thouroughly cleaned and cut out the black sealant used and have a new material welded in place.

Ed

 

If your roof is a Duro-Last roof, generally speaking you should not be using anything "black" on the roof. Petroleum based roofing products (which are usually black in color) are corrosive to the membrane and will damage the membrane over time.

Patches, repairs, TI's, etc. should be done using a hot-air welder and membrane material. In this process, hot air is used to literally melt the perimeter of a membrane patch over the hole/void, etc. No sealants or caulking would need to be used, especially petroleum- based ones.

However, this is not really a job for a newbie, especially as it involves patching very weathered membrane. The heat gun is not something you get at a Home Depot and the good ones cost about $500. Using a heat gun is an art in itself and takes some definite long-term practice to get proficient (we start our guys out by hand welding walkway - that way if they mess up it usually doesnt cause any leaks!). A patch that is correctly hot-air welded will not lift or separate as it is permanently fused to the existing membrane.

That said, since the roof is not warranted by Duro Last due to its age, you can do whatever you want. (If the roof is still warranted by Duro-Last, a Duro-Last approved contractor would need to perform the repairs to maintain the warranty) If you can get the black sealant off the membrane without damaging the surrounding areas, I would try and do so. Start by using water or simple green of something fairly gentle to clean things. You can work your way up through mineral spirits to MEK if needed, but be careful as the membrane is pretty old. Make sure you clean all the area where the new sealant will be applied. Sonneborn NP1, Sikaflex 1A or Vulkem 116 are all good quality sealants that will work to seal the patch. (Check you local roofers supply house for these)

BTW, congrats on getting 27 years out of your membrane roof. In my experiences Duro-Last seems to be one of the better single ply roof membranes on the market.

 

Durolast

Thanks for your responses. After i posted my question here I decided to look through the papers left for me by former owners in search of some other information, and amazingly I came across the original papers for the flat roof. It actually was put on in 1988 by a roofer who is still working in town. he did the roof on my former home. So I will call him (though he generally does not respond; he does lots of institutional jobs and he only did my home because it had a solid asbestos roof and I guess it represented a challenge, and he could make some money off me). In any case I will call him.

The roof was actually called an "At-Last" roof with a 20 year warranty. I tried to find them online but I assume that they were purchased by Durolast or simply went out of business. i did find the Durolast web site and get the impression that it is the same or a similar product. I think I am going to have to get the roofer to cut the patches off and put down some new product. There are several patches and I am wondering if it will be more cost effective to just put on a new roof.

How does this sound. If I cover the "At Last" roof with a rubber roof but do not adhere it with any glues or another. Just have the roofer tie it in with my new pitched roof and adhere it over the edge of the flat roof; the At Last roof comes right up to the edge and does not flap over.

 

Thanks for your responses. After i posted my question here I decided to look through the papers left for me by former owners in search of some other information, and amazingly I came across the original papers for the flat roof. It actually was put on in 1988 by a roofer who is still working in town. he did the roof on my former home. So I will call him (though he generally does not respond; he does lots of institutional jobs and he only did my home because it had a solid asbestos roof and I guess it represented a challenge, and he could make some money off me). In any case I will call him.

The roof was actually called an "At-Last" roof with a 20 year warranty. I tried to find them online but I assume that they were purchased by Durolast or simply went out of business. i did find the Durolast web site and get the impression that it is the same or a similar product. I think I am going to have to get the roofer to cut the patches off and put down some new product. There are several patches and I am wondering if it will be more cost effective to just put on a new roof.

How does this sound. If I cover the "At Last" roof with a rubber roof but do not adhere it with any glues or another. Just have the roofer tie it in with my new pitched roof and adhere it over the edge of the flat roof; the At Last roof comes right up to the edge and does not flap over.

Durolast is a PVC membrane, IIRC. Another layer of PVC, TPO or EPDM could be glued over it, but removal and replacement would be the smart approach. The approach you are suggesting is one method, but the new membrane would need to be ballasted (weighted down) if not fully adhered.

 

I don't know what type of membrane "At Last" uses, but it is important to try and get the same type of membrane for repairs, especially if you try and go the hot-air welding route. The original roofer is a good place to start. CU mentioned the "big" ones, but there are quite a number of different types of single plies out on the market that generally look the same to the untrained eye but have very different formulations.

Without knowing the size of the porch and how the At Last roof was installed it is hard to know if your proposed solution will work. I have only installed mechanically attached systems over the top of other mechanically attached systems and even then we slit the underlying membrane. I dont think that you would want to glue/adhere a new roof to the old roof due to the question of how well the adhesive would stick to the old roof, how well the original roof is attached, and compatability issues. Ballasting might work but would impose additional loads on your structure. Mechanically attaching might also work but you may have billowing or uplift issues if you only attach it at the perimter as you are proposing.

 

water based contact cement

How about water based contact cements. I have a cork floor in my kitchen and you cannot lay that with petroleum based products. It is a great adherent, though I am not sure if it is made for exterior applications. My floor has been down for probably 6 years with never a problem and even got flooded once, though it does have a water based sealant on it. Perhaps the problem would be any water that touches the edges where the patch meets the roof. I wonder if water could get in there. But the water based contact cement is really a very strong adherent so I wonder if it would be OK at those edges.

 

How about water based contact cements. I have a cork floor in my kitchen and you cannot lay that with petroleum based products. It is a great adherent, though I am not sure if it is made for exterior applications. My floor has been down for probably 6 years with never a problem and even got flooded once, though it does have a water based sealant on it. Perhaps the problem would be any water that touches the edges where the patch meets the roof. I wonder if water could get in there. But the water based contact cement is really a very strong adherent so I wonder if it would be OK at those edges.

You're trying to re-invent the wheel.

How big is this flat roof?

 

The roof is about 30 X 15. It is a nice size outdoo room. Just trying to do what is best. the opverall cost on replaceing my pitched roof is so high --can't believe how prices have gone up since I last replaced a roof!-- that i want to do what is best for the most reasonable cost.

 

At-Last Roofing Systems originally started by a former Duro-Last applicator and was located in LaPorte Indiana, who discovered where D-L purchased their original membrane sheets from and infringed on the D-L patents to promote it's product as a unique custom pre-fabricated roof system, just like D-L promoted.

At the time period you are referring to, they used the C-Ply membrane from West Point Pepperil who operated Bond-Cote membrane manufacturing and performed the collondering process to laminate the scrim reinforcement sheet to the bottom and top layers of CPA, also generically presumed to be a PVC material.

Any new clean D-L or Bond-Cote PVC membrane will be able to be welded in place like I suggested previously, providing that the existing membrane is cleaned of any and all contaminants.

Ed

 

Oh, btw, Custom Seal Membrane out of Ohio is also another former D-L contractor spin-off that estableshed it's niche in the same way, owned by a Father and Sons who previously where also high volume D-L installers.

Ed

 

Great information! i think I should work on finding an authorized contractor for a welded patch.

Thanks so much to you an the other people who have replied!

 

One other option is to use a coating to re-seal the patches if you can't find someone to heat weld them.

We use this product for a variety of temporary repairs. You'll need to find a roof supply store to purchase it.