roofer wants to use flashing pieces to cover knot holes in old

Brad White_68

If the garage is not heated there is no real differential of vapor pressure or temperature. Nothing to produce moisture to speak of and the only temperature rise you may have is residual from solar, the slab or your car. (If indeed anyone actually parks their car in a garage anymore... :) )

No worries about spanning over knot holes with flashing or tar paper. I have seen slate installed over skip-sheathing (sheathing across rafters with a few inches of space between, like strapping). Mind you this is even without tar paper; no leaks. My own shed has wood shingles on skip sheathing with nary a leak.

And Cosmo- Kimono is Greek in origin? I learn all sorts of things here. Cool. Next you will tell me that Baklava is Greek too!

D107

possible condensation problem?

hi,

having my garage roof replaced in tear off. Old wood has various knotholes, breaks. Roofer wants to use flashing to cover some of the holes to save me money on wood. This is not a finished garage, no insulation.

I was concerned about possible condensation/moisture onto this metal flashing.

D107

I guess if it's not heated, no problem, yes?

Cosmo_3

um

I am not sure I can help you here.

I assume the garage is not heated. According to your description the roofer is simply spanning over knot holes in the roofing underlayment with sheet metal. I don't see how this would affect anything as you described it, at least as far as condensation. Does the garage have an attic? Finished walls/ceiling? Garage heater?. But to tell you the truth, even if it was heated I still fail to see why a piece of sheet metal sandwiched between felt paper, and the roof wood underlayment would condense any more or less than the materials around it. I am assuming that there is no airspace.

So, I think I just wrote a bunch of sentences about nothing, er I don't know?

the word "Kimono" comes from the Greek word "Ximona". This means winter, and in the winter you can wear a skirt because is cold outside.....so,there you go

Cosmo Valavanis

D107

thanks cosmo

I'm happy to hear your answer, as the workers were right at that point. No finished walls, etc. or heat. If I ever do seal it and put heat in, insulation would probably solve any problems. When they tore off the three layers of roof on the 82 year old stand-alone two-car garage, I was amazed at the amount of knotholes, cracks, etc.in the tongue and groove sheathing. If it was the house i would have replaced all the wood. Roofer didn't seem to feel it necessary to caulk space where new wood met the old. I would think that in a house roof you'd want to have as few spaces as possible, that a thin piece of flashing over a crack was not as good an insulator as a 3/4" piece of wood.

Thanks again,

David

Cosmo_3

well

Your wood underlayment (tongue and groove wood) is not a vapor barrier. It simply spans your roof rafters, and provides a flat surface for the felt paper and shingles. The shingles keep water from touching the wood underlayment. The felt paper I think is both a 2nd water barrier, a moisture barrier (re- keep wood dry), and padding for the shingles.

Cracks in the tongue and groove are not a problem, I would not caulk them because the tongue and groove underlayment should be looked at as a "system". This underlayment system will expand and contract with outside temperature, and solar heat swings. The "cracks" give this expansion somewhere to go. Also the cracks help the roof breathe, helping dry out any condensation that might occur. The sheet metal your roofer installed I think was to simply span the open knot holes, to give a flat surface for the felt and shingles. I do not know whether this is standard practice or not, I am not a roofer!

New roofs covered with plywood have 1/8" spacers installed so that the plywood sheets do not fit tightly against each other on purpose, to give room for expansion!!

I am not a professional roofing contractor, I just tried to explain to you my understanding of how a roof works.

You can always call a local home inspector, or your local building inspector for more info (gee did you have a permit for the new roof? No? ...yikes!)

Cosmo Valavanis

D107

no permit required now but

I heard that the punishment for not having a permit was to force the homeowner to convert from hydronic to forced air heat.

Thanks again.

David

Cosmo_3

....

The term "Cruel and unusual Punishment" comes to mind....


Cosmo Valavanis

Cosmo_3

Hee hee

I didn't know we disagreed?

No, Kimono has absolutely nothing to do with the Hellenic lexicon... was just a funny quote from a movie; "Big Fat Greek Wedding", it was playing in the background this morning at a customers home, and of course I had the movie playing in my mind today.. The best part of the whole movie was when the brother would tell his future brother in law to say something to his future in laws in Greek, but would neglect to give him the real translation, thereby making quite an embarrassing scene

Not that I was ever guilty of that....

My only worry with the flashing is hopefully they remembered to hammer down the points on the 4 corners so it doesn't scratch the felt.




Cosmo Valavanis

Brad White_68

Damn.. I never saw MBFGW...

You got me, Cosmo. Duh.

Mike T., Swampeast MO

Nice explanation of a roof Cosmo!

Covering "knot holes" with flashing material is likely overkill and due to the conduction of metal might actually lead to moisture problems should the space ever be conditioned. Protruding nails are frequently blamed for this problem in colder climates!

If these are in fact "rot holes"--say a fist will fit through easily--I'd suggest replacing the affected wood...