ᐅ Who has experience with Bornit roof coating for weathered roofing felt?
Created on: 23 Oct 2025 14:33
F
FelixbauHello,
I want to restore a heavily weathered but intact roofing felt that shows some cracked deformations.
I had already ordered 2 buckets in advance because I read in the BSZ24 newsletter that using BORNIT roof coating would not be a problem. At that time, I thought the roofing felt was in better condition.
Is BORNIT roof coating still the best option in this case despite the recommended two coats (total approx. 0.8 l/m² (0.02 gal/ft²)), or would a filler-containing or fiber-reinforced product be more suitable for older bitumen substrates with slight aging?
Product: BORNIT roof coating, bitumen topcoat – available in 5 liter (1.3 gallon), 10 liter (2.6 gallon), 25 liter (6.6 gallon), or 200 liter (53 gallon) containers.
Thanks for your help.
Best regards
I want to restore a heavily weathered but intact roofing felt that shows some cracked deformations.
I had already ordered 2 buckets in advance because I read in the BSZ24 newsletter that using BORNIT roof coating would not be a problem. At that time, I thought the roofing felt was in better condition.
Is BORNIT roof coating still the best option in this case despite the recommended two coats (total approx. 0.8 l/m² (0.02 gal/ft²)), or would a filler-containing or fiber-reinforced product be more suitable for older bitumen substrates with slight aging?
Product: BORNIT roof coating, bitumen topcoat – available in 5 liter (1.3 gallon), 10 liter (2.6 gallon), 25 liter (6.6 gallon), or 200 liter (53 gallon) containers.
Thanks for your help.
Best regards
Hi,
You’re right to ask whether Bornit roof coating is a realistic solution for heavily weathered and cracked roofing felt. Actually, this roof coating is more suitable for slightly damaged, continuous surfaces rather than significantly aged bitumen membranes—otherwise, it might just cosmetically cover the condition instead of properly sealing it. Regarding Bornit: although it is widely used, it does not contain fillers or fiber reinforcement, so you can’t use it to “fill” or reinforce cracks.
Here, it might be worth considering a fiber-reinforced compound (for example, rubber-based or a cold bitumen compound mixed with fleece), because these accommodate typical material movements and bridge smaller cracks at the same time. Of course, you would first need to remove all loose dirt and dust from the felt. Have you tested adhesion on heavily weathered bitumen yet, perhaps with a small trial patch somewhere at the edge?
Honestly, manufacturers often explicitly advise that bitumen coatings should only be applied on intact bitumen when visible cracks are present. Renovating roofing felt eventually cannot be done with just a simple coating—the question is whether a complete re-roofing might be more sensible. How large are the cracks exactly (transverse or longitudinal cracks, open areas…)? Have you also considered incorporating fleece directly?
You’re right to ask whether Bornit roof coating is a realistic solution for heavily weathered and cracked roofing felt. Actually, this roof coating is more suitable for slightly damaged, continuous surfaces rather than significantly aged bitumen membranes—otherwise, it might just cosmetically cover the condition instead of properly sealing it. Regarding Bornit: although it is widely used, it does not contain fillers or fiber reinforcement, so you can’t use it to “fill” or reinforce cracks.
Here, it might be worth considering a fiber-reinforced compound (for example, rubber-based or a cold bitumen compound mixed with fleece), because these accommodate typical material movements and bridge smaller cracks at the same time. Of course, you would first need to remove all loose dirt and dust from the felt. Have you tested adhesion on heavily weathered bitumen yet, perhaps with a small trial patch somewhere at the edge?
Honestly, manufacturers often explicitly advise that bitumen coatings should only be applied on intact bitumen when visible cracks are present. Renovating roofing felt eventually cannot be done with just a simple coating—the question is whether a complete re-roofing might be more sensible. How large are the cracks exactly (transverse or longitudinal cracks, open areas…)? Have you also considered incorporating fleece directly?