ON Topic! Roofing felt adhesive

Surely it's just standard roofing felt glue you need isn't it? It's thick and black and gooey! :-)

I generally find that a good thick layer of the goo/glue and a few roofing nails works pretty well to add a layer of felt to existing felt. Just make sure that what's there is going to stay stuck down even if it's lost its waterproofness a bit.

Hot air gun to heat up the areas old and new and hotmelt glue sticks, melds well enough with the tarry stuff. Plus a block of "gone-solid" silicone sealant cut free from a delivery tube , to squash new and old felt and glue together. Been doing this for years to keep and old bit of flat-roof going.

You can get cold bitumen:

Today I've been doing some patching with this stuff:

The problems with past repairs like this is they haven't accounted for thermal expansion - you make them in one kind of weather (eg in the winter), and then come summer everything expands and cracks again. I can see the merits of the EPDM rubber roof, where the material itself takes up the expansion, and can cope with differential expansion compared with the roof deck itself.

Theo

There is only one suitable adhesive, bitumen. Get the liquid version in a can, it's not worth messing about with melting solid stuff.

OP here: Thanks a lot folks. Some useful ideas there.

I do have bitumen: "Wickes Brush-applied Roofing Felt Adhesive" -- the can is now probably at least a decade old, though I'm sure the stuff is as good as when it was bought.

However when I dug it out from where it's been hiding, I was surprised at the "Brush-applied" bit: what kind of brush are they thinking about?! I have never found it possible to use a brush -- I have to use a paint scraper to smear it as best as I can.

I thought that maybe there is something thinner that I _can_ brush on: it seems not (except unless I heat up this stuff!).

But anyway: your suggestions are indeed helpful, and appreciated.

Best wishes all John

Now here is the thing, it is only worth doing this before the stuff cracks, since the fact that is cracked reveals the integrity of the surface layer is not very good. I had a shed like that and tried using some felt over the top and water still got between them as even really gunky glue did not adhere due one supposes to the pitting and moss and other min bits of damage or debris. However some years later when my small shed needed re felting two layers with some kind of bitchimasstic stuff between seems to have more or less outlasted the shed. Brian

The black bitumen product I linked upthread can be brushed on, at least when new. I haven't had it for a decade but wouldn't be surprised if it were to congeal as some of the volatiles evaporate off. Perhaps some kind of organic solvent would freshen it up? Or just warming in a bucket of hot water?

The MSDS for the Everbuild stuff says: BITUMEN (WHEN IN SOLVENT SOLUTION) 50-70% WHITE SPIRITS, NAPTHA (PETROLEUM) 30-50%

so presumably that's what to dilute it with.

Although I notice Wickes now offer: Wickes Trowel On Roofing Felt Adhesive 5L so perhaps they just renamed their product to better describe it? That one is only 5-10% naphtha so not surprising it's thicker.

Theo

Add a bit of paraffin or buy a new can. Whatever brush you use goes in the bin after! I've put enough felt over cracks to know it mostly works fine. Biguns can be filled with sand + bitumen.

ISOflex used to be the bees knees until Ronseal bought it in about 1995, but it is still a very good product.

Have you considered a trip to a garden centre that sells EPDM pond liner in rolls ?. Local one sells it in a variety of widths off the roll by the metre. Just lay it on top and fix the overlapped edges with felt nails.

What a good idea Andrew!! I think I have a biggish square of pond liner buried in my sheds, somewhere, squirreled away 'in case it comes in useful'. I'll have a look at this option before anything else - ta!

John

Unfortunately EPDM is incompatible with bitumen. That means you'd need to strip off the old felt and re-deck or fit a barrier layer.

Yes I know. This is just an outdoor 'kennel' (presumably with a sloping roof) for logs. He can just loose-lay the epdm sheet over the existing cover and just rely on tacking the edges to secure it. A proper job would need a new deck like OSB3 but for this application, 11mm OSB3 could just be screwed(*) onto the existing roof and then the correct adhesive used

(*) Don't use nails in case they work loose with repeated thermal cycles.