Old asphalt flat roofs with blisters bubbles and cracks. Also painted in solar reflective paint 

Expert to the layperson...really Stephen.. a lot of what you say and are explaining as causation here in this video is unfounded.

Thank for sharing, keep safe

Very good video.

Greate job and thank you very much

Hi Steven. Thanks for all your interesting videos. Your video of the old asphalt roof with blister bubbles - I have a roof similar to this (perhaps not as bad, about half the number of blisters). Have you done a video showing how to repair or renovate this roof problem? I don't actually have any leaks, fingers crossed. Could I simply paint the complete roof with some type of high build bituminous paint and then solar reflective paint?

Nice video. An interesting material that is very blister resistant is asphalt emulsion with Bentonite clay ingredient. We have done tens of millions of sq. ft. and the stuff simply will not blister. It was explain to me by a chemist that its high perm rating is like Goretex skiwear. It allows vapor to escape but solids cannot enter. My son likens it to skin, which is waterproof, but allows moisture to escape.

Reason why that small roof is covered in blisters or to use the correct terminology 'Blows' is because it's been over layed with more asphalt by London cowboy asphalters, moisture is trapped between the asphalt layers, causing the blows, when you look at the close up you can clearly see it, but you wouldn't know that would you, because you know very little about Mastic asphalt, if it's done right it will last minimum 30 years.

I've been having this problems with my flat roof for a while. I keep it painted, re-silvering it every couple of years. But I've been getting increasing bubbles and cracks recently. I've been filling the cracks with flexible paintable sealant before painting over it (along with the rest of the roof). The bubbles are inside the asphalt, not something coming up from underneath..they're nowhere near the size of some in the video, but a lot of them go 'crispy' and split, leaving holes. I've been scraping off the broken bits from these burst ones, and filling the holes with paint (and sometimes sealant) to try and stop it from getting worse. But the bubbles just keep forming :(

Screw aluminum 1.2mm sheets over the top of the entire roof. This will flatten the 'blows' and give you a nice flat even surface. Then simply lay new felt over the top.

Is the secret to keep them painted

Can I felt over asphalt

Darren davies. That particular job shown on the video as been over laid, hence it's covered in blows, at no point was that mentioned, I was simply pointing this out, if mastic asphalt is crap as you put it, I wonder why there is whole industry built up around it, very strange, no it's not perfect i agree, but the new polymer roofing grades make for improved performance.I have been in the flat roof game 36 years, so please don't preach, it's very tiresome, all asphalt apprentices serve a minimum 4 years on site and at collage, and leave with a industry recognized qualification.Epdm. 1 day courseSingle ply. 1 day courseGrp. 1 day course

The bubbling roof at 1:20 - the main problem I would suggest is the parapet wall on either side which appears to be in very poor condition with missing mortar and brick spalling caused by the freeze/thaw cycle. There are also no coping stones on top. This has almost certainly allowed water to ingress through the parapet and get under the roof that has caused the damage.

There are a number of reasons that asphalt can start showing signs of movement, but generally the first place to look is the substrate on which it has been laid. Where you can see those straight/right angled splits in the flat, shows that this has been laid over insulation boards, probably over a timber deck as well. Without a decent solar reflective paint (silver paint isn't particularly effective) then not only does badly painted asphalt heat up in warm weather, the insulation properties of the deck will also cause asphalt to heat up further and start to move. In recent years, there has been progress with the addition of added polymers, to allow flexibility of thermal movement. The other signs, such as blows in the flat area of the roof and on skirtings are generally because of moisture, or if the surface isn't a decent key for asphalt to adhere to. On the flat, this is because moisture has got in between the insulation boards and causes the asphalt to react to any moisture evaporation in hot weather. This could be an issue with the vapour barrier that should be laid under the insulation boards. The skirtings on the roof lights shown in the video have blows in them because they are made of fibreglass and need to be primed with a decent primer instead of a bituminous primer or none at all, which isn't a decent key for asphalt to be laid to. Overall, I'd argue that silver painted asphalt probably isn't the best material for a warm roof.