ice/water membrane and/or flashing?

Old 04-04-02, 05:57 PM
Visiting Guest
Posts: n/a
Question ice/water membrane and/or flashing?

Iím having my house re-roofed - total tear-off. Iíve specified ice/water membrane on all roof overhang edges and all valleys. In addition Iíve specified aluminum drip edge along the overhang roof edges.

 Should I have them also install flashing in the valleys along with the ice/water membrane? The valleys currently donít have flashing Ė the shingles simply crisscross and overlap each other. Which is the best way?
 If I do use flashing, is aluminum good or do I need to have them use some other metal (cost is a bit of a factor)?
 Should any flashing go over or under the ice/water membrane?
 Do I need step flashing along the side of the roof dormer and around the chimney or can they simply us a single continuous length of flashing where those vertical surfaces meet the roof? My neighborís roofer recently used high tech sealant to seal the chimney flashing to the brick Ė instead of embedding it into the mortar lines. Is this an acceptable alternative?
 Any opinions on Certainteed laminated shingles?

Any other suggestions?

Old 04-06-02, 09:50 AM
Join Date: Dec 1999
Location: South Dakota
Posts: 2,999
Upvotes: 0
Received 0 Upvotes on 0 Posts
I will anser your questions in the order you asked them. 1. When the shingles criss cross each other, that is called a closed valley. I always install new valley metal even though it is a closed valley. Just an ounce of prevention that does not cost hardly anything. 2. Just use galvanized aluminum flashing minimum of 16" wide. In most cases I use 24" wide. 3. We usually put the flashing under the ice dam. 4. You can use either flashing around your dormer and chimney. Most use Blackjack with NEOPREME to flash with. It is relatively new and will last longer then regular Blackjack. 5. That is just about the best shingle made. I would get the new wind shingle they make. This one is terrific. Good for 90+ mph. A very good heavy shingle. Will last forever.
Old 04-06-02, 01:09 PM
Visiting Guest
Posts: n/a
After your roofing is removed, Install the Ice and Watershield directly to your sheathing. The code where we are located for the Ice and Watershield is it should be installed 24 inches past the exterior wall line which in alot of roofs means more than three feet high along the bottom of your roof. Also Ice and Watershield should be installed the entire length of your valleys directly to your sheathing then felt installed then shingles. The type of valley you have now is called a weaved valley and when you install your CertainTeed shingles the instructions for a Hidden valley is on the packages. Do not use aluminum, always use hot dipped Galvinized flashing do not cut costs. Yes you should use step flashings at your dormers and at the chimney area. After the step flashings are installed at your chimney a reglet is cut and counter flashing is installed over them. Never just use caulking or plastic cement around the chimney that is the sign of Sub-Standard workmanship and is not acceptable roofing practice. CertainTeed is a very good product with a very good warranty as long as you install them to meet their requirements.
Old 04-07-02, 01:53 AM
mrmojo's Avatar
Join Date: Jun 2001
Location: on the beach in nc
Posts: 313
Upvotes: 0
Received 0 Upvotes on 0 Posts
I was wondering where you could find galvanized aluminum
Old 04-07-02, 07:18 AM
HappyWoofer :-)
Visiting Guest
Posts: n/a
I agree with roofrat.If aluminum flashings are used then they must be secured with aluminum nails otherwise the gal. nails will corrode the aluminum over time.Another problem with aluminum is the expansion/contraction factor-greater chance of caulked areas cracking and valleys buckling beacause of the intense heat on the roof.I also agree with rugrat re:caulking-it's only meant as a backup-all my wall-flashings are cut/folded into the mortar joints and then caulked with Lepages Polyurethane Caulking-doesn't dry out and has a contraction/expansion value of 400%.And ALL step flashings should go over the ice and water shield-in this way the nails will be self-sealed which is the whole idea of ice/water shield.The reason some roofers use al versus gal metal is the al brake (folder) is only 200 lbs and can be taken to the job site.Gal metal brakes weigh aprox 4-8,000 lbs and cannot be taken to the site-all large folds have to be fabbed in the shop beforehand! In commercial roofing it is VERY RARE that we are allowed to use al flashings-99% of the time it's gal metal that's required because they are aware of the downside of al.

Woof :-)
Old 04-07-02, 06:47 PM
Visiting Guest
Posts: n/a
Thanks Everyone! One more question...

Thanks everyone for the good info. One follow-up question...
Is it better to use a closed/weaved valley (over membrane and galv flashing) or an "open" vallet with exposed flashing? I would think the layer of crisscrossed shingles provides extra protection - but I see alot of expensive homes with the exposed valley flashing. Opinions?
Old 04-07-02, 07:00 PM
Visiting Guest
Posts: n/a
Thats up to your tastes..If you do choose and open metal valley you can get them to match the color of your shingles instead of the galvinized look which turns grey and sometimes begins to rust. I think the closed valley looks best not the weaved ones but thats up to you. Good luck

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: