Underlayment for Shingles

[callmekc]

I am getting ready to shingle my roof on a new build. Instead of using felt, what material have you used that you've really liked as an underlayment?

[Tony]

old shower curtains

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[longshot]

tar paper

[DanG]

We have all used felt tar paper for many years, why do you want to consider otherwise? If you can afford it, you can install ice shield on the whole roof. It is self healing, but you will really need to do your homework on venting as the stuff doesn't breathe.

[Rod & Betty Jo]

I have a 10 by 25 ft 1.5/12 pitch shed type roof that has always had roll roofing.....It attaches under the 20+inch house eve with little clearance (just a few inches).......Anyway I'm planning on stripping it, laying on a new layer of CDX and was considering using ICE Shield over the whole thing.....the ceiling below is insulated but with little space between insulation and roof deck. It has no official ventilation (100 yr. old house with the addition probably 75yrs old)......Will eve only ventilation suffice, like in every rafter bay? If not how does one vent the top end on a nearly flat roof? Any cons or suggestions on the Ice shield? Thanks Rod

[marson]

First, you really ought to start a new post.

The topic of ice and water over the whole roof has been covered more than once in this forum. I believe that whenever you use a vapor barrier on the cold side of a structure, you could be inviting trouble, because moisture has no way to escape and will condense on the underside of the sheathing. Perhaps less of an issue with a well ventilated new house with a good vapor barrier, but more of a risk with an older house IMO.

However, you are in a tough situation. What are you planning to put on top of the ice shield? a 1.5 in 12 pitch is too flat to legally shingle. Your options are some kind of flat roof product like EPDM (there are other systems out there--EPDM is what is used where I live) or standing seam steel. None of these products would allow moisture to pass. I assume you don't want to demo the ceiling in there and fix the insulation/ventilation. Of course, if it has worked for 75 years, you might take the attitude that if it ain't broke, don't fix it.

I really can't say from here what soffit vents would do. Probably can't hurt, but I doubt it would do a lot of good if you don't have a vent space.

[Big_Jake]

If you have vent space, you could cut a ridge vent in half, and use it under a piece of flashing at the top as a pretty good vent. This would be in addition to a soffit vent on the bottom. I got kudos from my local building inspector for doing this on an addition to my house.

JK