Roof Underlayment

[showcrop]

(quoted from post at 05:12:12 09/12/23) Most steel manufacturers now recommend installing the screws on the flats right next to the ribs instead of on the ribs themselves to prevent that issue of screw holes enlarging. Even when screwed on the ridge, however, I've only seen that issue of holes enlarging on old, old barns with the
lead-shielded nails or the old-style of sealing washers, and old-style profiles. For many years now, steel profiles have been such that the expansion/contraction is taken up in the body between the ribs and thus the holes don't enlarge due to expansion/contraction. I have steel on 4 barns,
two machine sheds, and two houses (plus a couple of smaller fuel sheds etc.). The newest one is still 32 years old and shows no signs of leaking. The only one that has leaked is the oldest barn, with an old, 'wave' profile and the old-style of screws with the lousy sealing washers (the old
style didn't have the cupped washer over the rubber to sinch it down around the hole.

The last steel roof that I was involved with was replaced with shingles after around twenty years.

 

[dhermesc]

I looked at standing seam and steel shingles - the price was 4 to 6 times higher than shingles. Going with shed style roofing was a real possibility as several older homes along the street have just
that. It was still more expensive but if I thought I could seal around the chimney without it leaking I would have probably gone that route. Screw down 2X4 nailers and leave the old shingle roof as a
second layer and go. The big appeal was that I could have done this as a step by step process - now if I tear off the shingles I have to shake a leg and get at least half the house shingled as fast as
possible before a storm tears up the underlayment and destroys the ceilings with water leaks.

 

[Billy NY]

I didn't see it mentioned, one of the characteristics of ice and water shield is its ability to self-heal when penetrated by a fastener. Take a sample of the material you intend to purchase and poke a fastener through it then hold it up to light. It will seal around the fastener. On standing seam roofs designed by the state agency I work for, ice and water shield is specified to be applied to the entire roof. Been that way for 25+ years, and may also be a requirement by roof system manufacturers. Obviously, the standing seam type roof should perform without it, but is additional insurance as a secondary roof. They used to encounter a fair amount of problems with metal roofs on institutional, correctional and other buildings. They changed their specs and solved a statewide problem.

Pros/cons & cost, well it is a secondary roof that will perform. I believe this material has a time limit to be exposed before it is covered by the roofing materials. It's not necessarily required over the entire roof, unless part of a manufactured system specifying it. Did a 60 x 80 addition with standing seam roof, Firestone required full coverage of ice and water shield.