Sealing washers for metal roofing

Maybe buy the washers separately, like these?

If the edge degrades does it matter? Also, if the washer is dish shaped then you may have a "cutting" edge that could dig into the sheeting.

I'm not claiming either of those things is true. Just that you should consider them.

Maybe buy the washers separately, like these?

Good catch. Makes me wish Usenet had a thumbs up button.

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I think something deeper than a dish will be needed to give the needed compliance. Probably twice the depth-to-diameter ratio of most such parts.

Eventually light getting under the edge will degrade the gasket. It's unclear if there's enough meat on the gasket to seal against a screw that fits the hole. The idea is close, but the proportions don't look quite right and there's no good illustration.

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Is this raised seam roofing? I use corrugated galvy and plastic with the screws in the tops of ridges and not tightened enough to distort. It covers spaces that don't need to be completely waterproofed, warm humid early spring weather with snow still on the roof causes considerable condensation to drip from the underside, enough that the purlins were sliced from PT.

Areas that I clear with a DIY snow rake have wafer head screws that the rubber door seal bottom edge slides over.

The replacement washers I punched from red rubber plumbing sheet crumbled in sunshine but held up under the screw heads.

The 4' wide roof that partly covers the deck was hinged to the house and hangs vertical for repairs, I can easily reach all of it from a stepladder. The larger shed roof has every third 2' section separately framed as a removable hatch, allowing me to reach all the screws on the two fixed sections between them. One section of the deck roof is the same for easy roof access.

I think the gasket washer allows the roof to expand and contract while still sealing.

Sorta found what I'm looking for. It's called a "dome cap screw",

Thanks for reading,

bob prohaska

The only problem is you just made a hole punch. Guaranteed to cut the steel roofing in a short time - leaving big holes and a loose roof

Only if the bolt is grossly overtightened. Correct tension on sealing fasteners is critical, surface quality of the mating materials matters as well. Intallation manuals harp on the issue endlessly.

I realize there's no idiot-proof solution to the problem.

Thanks for writing,

bob prohaska

if the "cup washer" of the screw is tight rnough not to let ANY light into the elastomer it is close enoughto the dheet metal that any compression of the elastomer will allow movement of the sheet metal, whichWILL eventually compromisethe sheet metal They are designed the way they are for a reason - and the elastomer washer is not deteriorating enough from sunlight to affect the seal of the washer or the hold of the screw / sheet metal. You are trying to solve a basically non existing problem, and causing an almost definite one in it's place. They have been using those sheet metal screws for ofer 50 years - and they work. The old "lead head" nails were a different story - the pulled out of the wood in a strong wind and then the rood leaked (not much - they were on the top of the rifges - but enough to wet the joists, causing them to rot a bit, causing the nails to loosen more - etc) I've seen wind stormes lift sheets from barn roofs that were nailed - it takes a tornado to take a screwed down roof - and then it USUALLY takes the joists along with the steel.