Underlayment (15 lbs. or 30 lbs)

I have a 6"/12" roof that I’m putting architectural shingles on. I know 15 lbs underlayment is the minimum standard in the Spokane, Wa. area, but what would be the advantage of using 30 lbs. underlayment. I’m a DIY’er and I will probably working on the roof over a period of several weeks. Anybody have some insight on the underlayment.

I wouldn’t use either, I’d recommend using one of the synthetic felts. We switched exclusively to synthetic felt near the end of last summer regardless of the pitch. Safer to walk on, faster to install, lighter weight to handle and much better water proofing properties. I assume you’re also planning to use ice & water shield in the valleys, in other potential trouble areas and up from the eaves where gutter is installed?

In your case synthetic is the way to go.
It holds up better for longer.
It doesn’t shrink and it is more wind resistant.

I prefer Titainium UDL but all the synthetics I have used were pretty good.

Agreed with the 2 previous posts.

However, if you for some reason had to go with felt, 30# definitely. Rips less, easier to apply and the cost difference is minimal.

Never rip off more than you can re-shingle by the end of the day and always have a tarp at the ready.

Three smart guys!

Who do I make that check out to Bam?

LOL

here in florida the residential roof code has been changed to a peel n stick or ice and water shield and striping the edge metal also.its a better seal if water intrusion occurs under the shingles and makes for a tight seal at all nail penetrations. 30 lb is a thicker mil. you can use that or 2 ply a 15 lb. i know people in the north who also 2 ply the 30 lb. felt, however i am a fan of the synthetic also.

Whens the last time you touched a roof?
this is roofing.com, not general contracting.com

[quote="-Axiom-"]

In your case synthetic is the way to go.
It holds up better for longer.
It doesn’t shrink and it is more wind resistant.

I prefer Titainium UDL but all the synthetics I have used were pretty good.[/quote]

Has anyone used tri-built synthetic (www.alliedbulidng.com)underlayment?

I really like the Atlas product Gurilla Guard. It is a synthetic product. It lays flat during install has the same weight as 30# but holds up much better.

im in florida, peel and stick is not code. it was about 2 yrs ago but they changing it back to felt,it just has to be nailed tighter, 6" on laps and 2 rows of 12" rows stagered.

6/12 is a good slope and the 30 is thicker and will be more secure.

gweedo.