Bitumen felt roofing washers HELP!!!!!!

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Established Member
4 Dec 2021
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Gogledd Cymru
Hi all. Just going crazy trying to find square or diamond bitumen roofing washers that fit under the square/diamond curved washers when fixing he sheets down. I've always been able to get them from roofing supply shops/websites, but I've drawn a blank so far. The trouble is, I don't know what they're called and if you type in bitumen roofing" or any other likely useful phrase, Coroline roofing comes up. Does anyone know what they are called?

My stable roof is partly on using the many I had left over from an earlier job so I want to use the same method. I've removed some earlier applied panels and the bitumen washers have a really shiny smooth area where they've been crushed and then heated by the sun; a perfect seal and has been so for decades.

If anyone is interested in the Heath Robinson method that I, as an amateur roofer who is petrified of heights above 18", has developed that works here in the North Wales mountains overlooking the Irish Sea that has worked well for over 30 years on an earlier project on the mountain, here goes (feel free to 'shoot me down in flames if you know what you're on about as I don't!), here goes:

  • Timber frame, traditional corrugated zinc sheets (.9mm) 30ft+length, single incline.

  • Screw fixings, even modern ones, work loose and never retighten effectively again, twist nails are pointless and anyway, I hate going on roofs so much, I don't want to go up again, especially in wind speeds that have been known to reach 3 figures, (that one did destroy a Welsh slate roof though!).

  • So, instead, I drill the sheet just in-front of the 7" timber joist, etc. that one would usually screw into.

  • Then I drill through the timber about 120/150mm down and push a coach bolt through the hole and attach an eye or J-bolt to it via nut with the threaded portion, now poking through the sheet. I then attach one bitumen and 38mm curved metal washer to the other side and use a nylock to hold it down.

  • One in every up-corrugation on a leading edge (especially the south-west facing ones), and every-other thereafter. Massive flashings (they really are ugly) and a bead of roofers bitumen in-between overlaps.
Like I say, I'm no expert but my logic is that the pressure required to tear the coach bolt through the timber, or even the .9mm sheet over the thick 38.40mm profiled washer and bolted down is so huge that even I can relax when it is howling outside.

So, if you've read this far and the tears of laughter are running down your face at my inexpert Bodge the Builder method of roofing, you likely know what you're on about so may know what these damn diamond/square bitumen washers are called. Please humour me and put me out of my misery so I can search the interweb for them

Many thanks/Diolch mawr
Why the eye or j bolt?

Not sure I it's purpose over regular coach bolts?

Would self adhesive plashing work the bitumen would create a seal?
"Not sure I it's purpose over regular coach bolts?" Apologies, I should have mentioned that I drill through the timber at 90 degrees, so if using a 7"x2", it goes through the 2". The coach bolt poked through the hole picks up the J hook which, pokes up through the corrugated sheet with bitumen, curved washers and DPM washers all held on with a nylock. It'd make more sense with a picture than my rambling, I'll take my camera-phone out and try to take a few explanatory pics in the next day or two.

The self adhesive bitumen flashing is a great idea Thanks! The originals are just thin roofing felt squares or diamonds with a hole stamped out for the fixing (M8, M6 etc), buying a huge role of felt is a waste and flashband etc, will do the same job for sure.