Hello - new to the forum and wanted to get your input. I am repairing an open (woven) valley - after I remove the shingles woven in the valley, do I need to lay down a new underlayment (self-adhesive or standard underlayment) before replacing the removed shingles with new shingles?
If so, do I need to cut/remove the existing underlayment and lay the new underlayment on the sheathing, or do I put an adhesive underlayment on top of the existing underlayment?
Thank you for the reply - I really appreciate it. Just to clarify, it seems like there is a layer of felt on top of a layer of adhesive water shield - so I should cut back the felt (and remove), and then remove as much of the water shield, and then put new water shield down (I read 36" wide at a minimum" - should I then put new felt on top of it (and tuck it under the edges of the remaining felt that is still under the asphalt shingles)?
Thanks for the help - I appreciate it; I’ve found conflicting information online - some said to leave existing felt/underlayment and put a new layer of felt on top running with the valley - and some said remove existing and put new adhesive water shield against the sheathing.
Depending on your shingle manufacturer there will be different requirements and approved techniques, that being said almost all agree with certain basics:
Ice and water shield as base layer in the valley 24" min. 36"+ best practice, centered on the valley and extending from the eave up 12" past the starting point of the valley with some recommending 24".
No nails within 6" of centerline, preferably within 12" of centerline.
If you must overlap IWS, overlap pieces by 6" and roll it to get any possible bubbles or creases out.
When overlapping over roof deck covering (felt, synthetic deck guard) overlap by 6" on the new IWS and on the old deck covering, make sure if any of these run into a hip or ridge they extend up and over as well if possible.
Be certain your roofing surface is clean and dry before doing anything, (and expect that wind will blow granules and debris at you when you are putting new stuff down so take account for this when putting new material on - start windward)
It is better to extend it beyond and trim it back than to try and piece things together.
This is a repair so some of what you have been reading may not directly apply.
Read the instructions on the package, keep in mind this is just a puzzle and all you need to do is remove and replace some pieces, don’t over think it.