6 mil plastic under shingles

An agent asked me a question .
What are your thoughts .
He has a home Listed and they had a home inspection .
The inspector said that there was 6 mil Plastic on top of the sheating and under the shingles .
What are your concerns or thoughts please will let you know what the Inspector said after I get some of your ideas… … Roy

The plastic could cause moisture to build up between the plastic and sheeting. Tar paper breathes, plastic does not.

condensation would be my concern as well…

How long before the wood rot starts?

And how did the inspector verify this?

Does not meet IRC requirements.

ditto time for a new roof if the entire home is like this, rec roofer to insp. will need to spot check the roof and take up shingles ect…

That’s just plain wrong! The wood will probably rot quicker than the shingles will deteriorate.

I just had my roof done and they used a new product that is completely water proof in fact it is so good if you do not put on shingles for a month it does not leak .
Now I wonder why sheeting has not decayed under ice and water shield as it does not breath . The only thing I see wrong with Plastic is it could be slippery when walking on it . Below is from a Professional .
[FONT=Calibri]Underlayment being used is
RoofGard-Cool Grey



RoofGard-Cool Grey rolls are lighter and easier to handle making it faster to install. The synthetic, non-breathable material is completely waterproof and effectively sheds water that gets behind shingles or alternative roofing materials. RoofGard-Cool Grey can be used as a temporary roof covering for up to 6 months without break-down or performance loss.

Same as the new product Grace has.
Grace TRI-FLEX® is an innovative spunbonded polypropylene coated with a layer of U.V. stabilized polypropylene on both sides. This technology, available only from Grace, creates a very durable and tough weather resistant fabric. It has excellent tear resistance, designed to withstand even the strongest wind conditions.
[/FONT]It will not rot out the sheathing anymore than the products we use regularly. If you can stand on it is the problem.

Underpayments with a perm rating of 1 or less are moisture barriers. Underpayments rated above 1 are moisture readers.
Polyethylene 4-10 mils has a permeability rating of 0.01 and the perm rating of most self-adhered membranes is about 0.05.
None the less, like I mentioned above, anything less than 1 is a moisture barrier.

Ice and water shield membranes, poly, tarps, and anything waterproof is made for a temporary roof. Has nothing to do with the rotting of plywood or OSB, but what does is improper attic ventilation to rid the attics of moisture laden air, which sure as hell will rot the plywood over time.

So to make a long story short, big deal with the poly under the shingles. The inspector did not do his homework on Building Science. A know Public Fact.

That help?? Ha. Ha.

So those roofers without fall protection gear know about deeper secrets of physics than we mortals…in their special world, gravity must make things fall upwards…DUMB…DUMB…DUMB.

The sheathing would still breath downward so it may not be so bad. That being said, there is a big difference between poly and Ice & Water Shield. The Ice & Water Shield is fastened to the sheathing with adhesive so condensation can’t get between the two layers.

What about the new non breathing products like they used on my home . They seem to be loved by all roofers and they being used a lot.

Sorry Brian that was not the question… Evade evade evade .

My point was that the sheathing would still breath downward even with poly. Not quite sure what you are asking me here. The product on your home is also peel and stick like Ice and Water shield?

No it is not it is very thin and dry on both sides . Thats one of the big advantages it is very light and easy to put on .
I also asked the question and put it on so many can learn about new products and how well they work .

Amazing that it will stay on the roof for several months without shingles on top of it.
Thanks for the information.

I like that,as frequently it rains and the roofers are trying to get out tarps to try and protect the sheeting .
This stuff goes on so easy and is so light in The company flyer it tells about how there is a huge labour cost saving.
My roofer cound not say enough good things about it .
I have a sample and tried to tear it . I could not.

Roy, that product is not a substitute for eave protection. Just thought I would mention.
And here are a few addittional notes;


[/size][/FONT][FONT=GillSans][size=1][FONT=GillSans][size=1][size=2]This product is a vapor retarder,so the airspace beneath the roof deck should be properly and thoroughly ventilated to avoid risk of
moisture condensation.

**[FONT=GillSans-Bold][size=1][FONT=GillSans-Bold][size=1][size=2]The following installation recommendations should be followed for best roof performance:

  1. [/size][/size][/size][/size][/size][/FONT][FONT=GillSans][FONT=GillSans]The roof deck must be swept clean and be smooth and dry before installation starts.
    [FONT=GillSans-Bold]2. [/FONT]*[FONT=GillSans-BoldItalic][FONT=GillSans-BoldItalic]IKO RoofGard-SB [/FONT][/FONT][FONT=GillSans][FONT=GillSans]synthetic underlayment should be unrolled and laid flat to the roof deck,horizontally (parallel to eave),starting at
    the bottom of the roof with the printed side up.
    [FONT=GillSans-Bold]3. [/FONT][FONT=GillSans][FONT=GillSans]There should be minimum,4" (100 mm) side laps and 6" (150 mm) end laps.
    [FONT=GillSans-Bold]4. [/FONT]
    [FONT=GillSans-BoldItalic][FONT=GillSans-BoldItalic]IKO RoofGard-SB *[/FONT][/FONT][FONT=GillSans][FONT=GillSans]synthetic underlayment is attached to the roof with roofing nails or staples having 1" (25 mm) diameter
    plastic/metal caps. Fasten with enough fasteners to safely hold the underlayment in place until shingle application. Additional fastening
    should be considered if shingle application will not take place soon thereafter.Typically fasteners should be spaced at approximately
    8" (200 mm) on center on both side and end laps in normal wind zones. In high wind zones or coastal areas,fastening spacing may
    need to be doubled to 4" (100 mm) on center; check local building codes.
    [FONT=GillSans-Bold]5. **[/FONT][FONT=GillSans][FONT=GillSans]In all cases,fasten at approximately 24" (600 mm) on center down the middle of the roll in the field of the roof[/FONT][/FONT][FONT=GillSans][FONT=GillSans].[/FONT][/FONT]

Thanks Marcel . Looks to me like they did put Ice and water shield on . they also installed 3 new vents and a new toilet vent flashing . reinstalled the existing eave starter

Yeah, I see it, I thought it was #15 felt from striping the roof.
Hey, plywood looks good, and has h-clips too. Wow. :mrgreen:

Good clean roof.