Roofing material for flat slope western pacific northwest

Question

10 months after purchasing a manufactured/RVIA certified home the, landmark arch, ridge venting shingle roof began to leak, with water leaking out of the crevasses of the main beam.

A roofing contractor that our home manufacturer sent mentioned the material used isn't suitable for such a low pitch, a flat roof at 2:12. The contractor initially patched the flat ridge line so it folded to the roof, the same night after the patch the leak came back even worse. The second time the contractor came back, he completely removed the ridge line, and sealed it with tar striping. There doesn't appear to be any venting in the ridge now though.

The roofing guy seems confident that should be sufficient, however their initial conviction that the material was a mismatch makes me think the manufacturer might have convinced him to be quite so the problem could be fixed enough for the duration of our warranty period, 1 year.

We live in the western pacific northwest (wetlands) and recently removed all tree branches close to the roof to prevent damage.

Is the roof/vent approach, see image below, and asphalt material the necessary requirements for this roof?

If it's not, what is the likelihood we'll need to replace the roof in the near future?

Answer 1

Your shingle manufacturer (CertainTeed) specifically states that your roofing material should not be used for 2:12 pitch (which, BTW, is not flat as you state in your question). However, the instructions also seem to contradict that later.

Limitations: Use on roofs with slopes greater than 2" per foot. Low-slope applications (2" to 4" per foot) require additional underlayment. In areas where icing along eaves can cause the back-up of water, apply CertainTeed WinterGuard™ Waterproofing Shingle Underlayment, or its equivalent, according to application instructions provided with the product and on the shingle package.

Bold emphasis mine.

Now, it is listed for slopes greater than 2:12 but with specific instructions for underlayment on "low-slope" applications.

I would pay a contractor (not the one that did the warranty repair) to ascertain the exact slope and for them to put it in writing; tell the contractor why.

If it is:

• not greater than 2:12 you should demand a complete reroof by sending the home manufacturer a certified letter accompanied by the contractor's statement. If the builder does not respond have a lawyer send them a letter. If they still do not respond take legal action.
• greater than 2:12, have the contractor ascertain whether or not the proper underlayment methods were used. If not, see above.

There is also the question/problem of ridge vent removal. The manufacturer specifies the use of ridge vent combined with soffit venting; however, if the vent configuration meets normal standards for your area and roof size maybe that's not a deal-breaker.

Answer 2

Several issues: 1) I think we're arguing over the term 2:12. Actually, Certainteed says "between 2:12 and 4:12" and gives specific specs for installation. However, I think they allow their shingles down to 2:12...slight variance, but acceptable by Certainteed. I know this because the underpayment they recommend, Winter Guard, they say to use under shingles at 2:12 and up to 4:12. In any event, you'll need to calculate the slope exactly. You can use a carpenters square and a level, but be sure the roof is uniform slope. I've checked roofs where it's 2:12 in some locations, but not a full 2:12 from top to bottom. (If it's close, you'll need to measure ON THE PLYWOOD SHEATHING NOT ON THE SHINGLES.)

2) UNDERLAYMENT: Certainteed requires specific types of underlayment depending on the slope. Odds are, the contractor used standard building paper, not WinterGuard. Winter Guard seals around nails driven through it to hold the shingles down. (Costs more than building paper too.)

The underlayment is suppose to be turned down BEHIND the gutter with the eave flashing placed on top of the underlayment and lapped into the gutter. I don't like that because water can get under the shingles (that's why we install underlayment) then run down and get under the eave flashing...but it's what the manufacturer requires...

3) OVERHANGS: Certainteed requires a "peel and stick" underlayment for slopes 3:12 down to 2:12 and extend up (I think) 24" up from the eave line. (Extends higher in high wind areas and low slope conditions. If you're west of the Coast Mountains I think that is considered"high wind" area. Check with building codes...they have a map and check with manufacturer.) doubt you'll find they did that.

4) SHINGLE EXPOSURE: shingle exposure is reduced for low-slope and/or high-wind applications. Verify your roofer followed guidelines for the brand/model shingle installed.

5) VENTS: individual roof vents are only recommended down to 3:12. (If you can find a manufacturer that allows their roof vent on anything under 3:12, let me know. ) actually, you may need to go back to the ridge vent, because some (with wind diverters) can be used down to 2:12 and the building code requires (I think) 50% of the venting in the upper half (maybe it's 30%) of the roof with the remains in the lower half (soffits). So, whoever removed the ridge vent needs to replace it. (There is a way to build curbs with step flashing, etc. and place a "roof cap vent" on the curb, its expensive.)

6) NAILING: if you're in high wind area, more nails are required per shingle. Also, verify exact location of nail in shingle...they reduce space to butt of shingle...also why they reduce "exposure". See above.

7) CODE AND COMPENSATION: the building code has specific requirements and I've yet to see a roofer understand and follow them. They do what they did last time and usually I'm called in to clean up. The roofer must be licensed by the state. Contact the Builders Board in your state. (If they are not licensed through the State, I've heard you do have to pay them...but you'll need an attorney for that one.) Also, they will have a bond that you can attach through the Builders Board. The Board will assist you in filing a claim against this yeah-hoo, make a determination and then award you compensation, which the bond may-or-may-not fully cover. Go to the manufacturer's website, read the "installation guidelines" and check each item ... item-by-item. I've yet to see anyone install shingles EXACTLY how the manufacturer has specified.

Let's see...you asked if the life expectancy will be reduced??? Yes and you'll be fighting leaks every time one of those storms roll into the northwest.