Roofing a lower slope question?

BusterMN · 04-11-2011, 05:53 PM

I will be shingling a new addition roof with in a week. The pitch is a 3.75/12. My first question is should I run I/W all the way up to the ridge since it is a low slope? I live in Minnesota so a lot of snow and rain is factored in. Should I then do 15# felt over the I/W? Also what should I vent with on that low of a slope, a ridge vent or box vents. I will have one open end gable and the other gable is against the existing house wall so would I wall vent the gable end too?

PS: I will be installing architectural shingles.

Thank You for any suggestions.

seeyou · 04-11-2011, 05:59 PM

3 tabs or dimensionals?

In KY, I'd not use the I&WS, especially with dimensionals. Hopefully someone with local MN experience will chime in.

I've had trouble with some brands of box vents on similar slopes. I'd probably opt for the ridge vent and the gable vent or make sure that the box vents were rated for less than a 4/12. I think most ridge vent is rated down to 3/12.

rossfingal · 04-11-2011, 06:26 PM

I'm in the "Midwest" area.
Ice and Water Shield, then the shingles - no felt.

rossfingal

Artic50000 · 04-11-2011, 10:22 PM

I would Ice and water the whole thing than depending what the roof looked like would do a 4" lay on the shingles.

Roofmaster417 · 04-11-2011, 11:40 PM

Since ice and snow are a factor in your region. I would use the I&W and then I would use felt over the I&W.

When I&W is used IMHO felt should be applied over the I&W.My reasoning is from a roofers stand point.When the moisture guard is applied directly then shingles only are applied the next reroof it will be almost impossible to remove the shingles.

Someone mentioned lowering the exposure.(exposure is the part of the shingle that will be exposed to the elements)

Most shingle manufactures allow this method for lower slope roofs.The usual exposure of an arch shingle is 5-5/8".

So lowering the exposure would be 4-5/8" instead of 5-5/8" after the reduction.I have used this technique with no problems.Check the manufacture requirements pertaining to lowering the exposure.

Lowering the exposure creats a thicker more solid roof for the lower pitch.

One thing to remember if the exposure is lower you will need more material.(Shingles).I would add 1 bundle for every 1.66sq.

Since you do have snow and ice with your region I would also recommend starters on your rakes.

For your ventilation I myself would use a RidgeVent with snow guard to adapt with your region.You can go back several pages on this forum.What you will see is posts about snow entering the attic from vents.

A RidgeVent with snow guard will keep your attic clear of snow.

Artic50000 · 04-12-2011, 08:42 AM

Quote:

Originally Posted by Roofmaster417

S
When I&W is used IMHO felt should be applied over the I&W.My reasoning is from a roofers stand point.When the moisture guard is applied directly then shingles only are applied the next reroof it will be almost impossible to remove the shingles.

So lowering the exposure would be 4-5/8" instead of 5-5/8" after the reduction.I have used this technique with no problems.Check the manufacture requirements pertaining to lowering the exposure.

as far as the tear off not coming off later that is kinda a good thing meaning that there is a good seal between the I&W and the shingle. Felt has to be held down some how which mean more penetrations in the I&W and roof system period. If you do the roof correctly you shouldn't have concerns of tearing in off any time soon.

as for exposure.. good point I should have said 4 5/8" we just call it a 4" exposure but mean 4 5/8" instead

JT

Roofmaster417 · 04-12-2011, 10:19 PM

Quote:

Originally Posted by Artic50000

Felt has to be held down some how which mean more penetrations in the I&W and roof system period.

If you do the roof correctly you shouldn't have concerns of tearing in off any time soon.

JT

The roof system IMHO is made up of 3 categories completing the "Roof System"

1.) The solid allowable roof deck which the underlayment is applied to.

2.)The underlayment over the suitable roof deck

3.)The allowable by local building codes roof covering that is fastened to the underlayment fastened to the allowable roof decking..Allowable meaning your region.Also allowable according to local building codes federal and state requirements.

IMHO the moisture guard should not be the only form of underlayment.
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True if a roof is installed properly then a reroof should not be needed anytime soon.,,,,,,,,,,,,,,,,,,,,,,,,,Agreed

But if a roof is installed properly WITH felt and moisture guard (I&W) then the complete roof system should reach its maximum lifespan.

I understand and partially agree with your concept completely,,,,but lets be real here.Unless you live somewhere that is free of Hail,Tornado's,straight line winds,severe snow and ice that ALL can limit a roofs longevity then I feel that you should think long term.

In the event of any storm related issues that a roof thats installed to your specifications,(agreeing with you 100% but thinking longterm) falls into then the result could be as follows.

1.) The roofer will have a MUCH more difficult time reroofing.What if? and this has happened to me numerous times that you are called to reroof a home that you reroofed due to storm damage?

2.) Almost 2 times the amount of labor could be incurred from labor alone.

3.) If the roof is unable to be removed then a recover could result,,,creating more weight and issues with that go with a recover.

4.) Trying to remove the roof that is sealed to the decking the customer can receive some added expense from gouging the decking etc.

5.)The contractor can be required to replace any decking that has been gouged or damaged from trying to remove the old roof.

6.)Once the contractor or homeowner has incurred cost replacing damaged decking from trying to remove the old,then the replaced decking areas will have a void or sunken area where it meets the roof that still contains the moisture guard (I&W).

7.The felt can be applied with either button caps or staples.On a low slope the need for over cap nailing should not exist really limiting the amount of holes in the moisture guard(I&W).

8.) Use 3/8" staples for the felt application.Staples will not create such a hole that won't be sealed back up from the moisture guard (I&W).

IMHO apply felt OVER the moisture guard (I&W) and help the next guy reroofing the home or even yourself.IF you have ever replaced a roof that had only moisture guard (I&W),,,I think this conversation would be nonexistent.

Grumpy · 04-19-2011, 05:44 PM

I am not a fan of ice shield on the whole roof. I have done this in Chicago and had mixed results. Entire ice shield can act like a vapor barrier and if the ventilation isn't perfect you will have condensation problems in the winter time. If you read the certainteed instructions they call for a double layer of 15# minimum. I often use 30# and have recently switched to the winter guard fiberglass reinforced which has a less permebility rating than 30# meaning it'll have less chance of leaking.

I'd double course the ice shield, meaning if 3' meets minimum code I'd install at least 6'. Then felt and make sure ventilation is perfect. Don't install a ridge vent at 4/12 or less in snow regions in my experience. I've had problems with snow backup even using the premium baffled ridge vents. If you do use a ridge vent make sure to place a bead of caulk beneath to prevent snow back up beneath.

In years past I used to adjust the exposures on shingles which worked well with 3 tabs. However if you consult your manufacturer rep you will find this is an instant void to the shingle manufacturer warranty since I have personally never seen a spec that allows for this technique. Therefore we have ceased use, and wouldn't ever consider it an option with laminated/architecturals.

brenda o · 04-21-2011, 10:30 PM

great post! is a vaulted roof on a manufactured home less that the 41/2 slope you guys are talking about? i'm wondering about the ridge vent on my home, western ny winters and roof in process of getting done. they just did the i/w shield, i don't know if they are doing felt next.... they will be here tommorrow.... i should have gotten on here earlier.....

Grumpy · 04-21-2011, 10:59 PM

mobile homes in mya rea are 2/12. Anything's possible though.

onarooftop · 04-21-2011, 11:00 PM

First question should be is your addition heated. If it is a 4/12 and not heated. You do not need
to have ice-guard.I would Double check the roof pitch. Most likely it is a 4/12. I am suprised if it really is a 3.75/12
Keep it simple. Ask the roofing company if they are installing the ice-guard to the manufacturers specifications.
As far as another layer of felt over top of the ice-guard?, I haven't seen any manufacturers recomend that.
If you prefer that to happen then I would ask the roofing company how much it would be, because I imagine it wasn't in the
original quote.

SeacoastRoofing · 04-22-2011, 05:59 PM

I just discovered a new application called TPO, which is for low slope & flat roofs. However, I cannot comment on its quality yet. Can anyone recommend it? I hear that it comes it various colors also. If you are looking to prevent ice dams - here a resource. http://www.seacoastroofingnh.com/icedamcure.html

brenda o · 04-28-2011, 11:35 PM

just the explanation i needed! thanks