Roof Decking Question for Roofers

[danieldd]

I'm having the roof decking replaced with 7/16" TechShield and architectural shingles on my ranch house.

Here is my concern…

The roof pitch is 4/12 slope. The rafter spacing is 24 inches. Currently it has 3/8" decking (this is what they used on my house when it was built in 1972).

A square of 3 tab shingles weighs 230lbs. A square of architectural shingles weighs twice that, approximately 430lbs.

Code says we should use 5/8" decking, but it would have to be ordered and is an additional $1500 extra. I can't justify the extra expense and am thinking of just going back to 3 tab shingles, but I like the look of the architectural shingles. Our roofer believes 7/16" decking, including the use of clips will suffice with architectural shingles and there is no need to use 5/8" decking.

I'm concerned about the extra weight of the architectural shines due to the 24" rafter spacing. Any ideas on whether this is a concern or not?

 

[Jon_E]

Purely opinion but based on 25+ years of construction experience: spend the extra money and use 5/8" T&G decking. Notwithstanding that it's stronger and less likely to sag, especially with 24" center-to-center spacing of your rafters, why would you not build to code?

 

[danieldd]

Purely opinion but based on 25+ years of construction experience: spend the extra money and use 5/8" T&G decking. Notwithstanding that it's stronger and less likely to sag, especially with 24" center-to-center spacing of your rafters, why would you not build to code?

Thanks for your input. It is appreciated. To answer your query, would like to meet code, but the extra expense is bothersome. It is already costing me $12K out of my pocket to have the house decked/roofed.

 

[ldl]

Do it once and do it right or it will cost you more down the road.

 

[spudley]

My original roof (1984) was decked with 7/16" ply and covered with 3 tab asphalt shingles with clips, ordered by my brilliant architect. I can clearly see the sag between 24" centered trusses every time I pull on the drive.
Built a cottage with 24" rafters and used 5/8" OSB, the heavier architectural shingles 20 years ago and it is as flat as the day it was installed.
Guess what I'd use?

 

[vavet]

Wow...I had no idea architectural shingles incurred such a weight penalty. I spec-ed those for my last house when it came time to re-roof without ever considering it. None of the roofing contractors I spoke to ever mentioned it. I still have that house as a rental property. Hope it's OK.
New house also has it but it was built in 2015 knowing we would be using architectural shingles. Hopefully they took that into account with truss design/sheathing.

 

[bpjr]

The extra weight of architectural shingles on 7/16 with a 24" span is worse than what you already have. That extra 1/16 thickness gives so little extra strength that both 3/8 and 7/16 have the same max span rating...which is 24". I'd find a way to get 5/8 so you meet code and won't have to worry about it.

On the other hand. You already know what 3/8 with basic 3 tab shingle will do. If that has been acceptable stay with it and save $.

 

[CNGsaves]

Whatever you do . . . do NOT go with OSB decking. It's VERY much worth the extra cost of plywood. Negotiate a deal for entire roof with plywood . . . or the tongue & groove that above poster mentions . . . but PLYWOOD.

My friend's house had maybe 2/12 pitch and I replaced around 30 sheets of 4'x8' decking on that house due to rot - - - this was 33 sq roof. I used 1/2" plywood that cost between $18 to $20 per sheet (Lowes and local lumberyard). No clips were used and not tongue & groove . . . however all joints were staggered (common roofing practice). Rafter spacing was 24" on center. The plywood sections I did are very firm now, compared to the OSB that remains from last roofer is little spongy. Tamko architectural shingles were used along with ENTIRE roof covered with Ice & Water dam underlayment from Menards.

Also, make sure that proper nailing of decking is done with 2 1/2" or longer ringshank nails . . . absolutely no staples.

You will be fine with ONE layer of architectural shingles and the 1/2" plywood or 7/16" tongue and groove plywood on 24" center rafters. Just have shingle delivery company spread out the new shingle bundles all across the ridge . . . to even out the weight.

+1 for . . . . Do It Once . . . . Do It Right !!

 

[strutaeng]

Code is based on the span rating of the decking. Code is MINIMUM. 7/16 meets the 24 spacing rating for roofs. That's what all the houses around here get. I personally would go with 19/32 or greater.

My house has 1x10 pine boards for the roof decking, while my garage has 3/8" plywood. The garage has visible sags and is more "bouncy." However, the only time I can see this is when I walk on my roof. Both carry the load. Both are 24" o.c.

Why don't you keep the existing 3/8" and add another layer of 3/8 or 7/16 OSB or plywood? Just make sure the new decking is staggered from the existing and nailed into the rafters. This is what I plan to do to my garage when I re-roof.

Good Luck.

 

[GMCGarage]

Will it void your warranty?

 

[patchap]

What shingles are you using that weigh that much?
Standard laminate shingles weigh 240-275lbs.
Premium shingles like Certainteed Grand Manor weigh closer to 430, but theyre the heaviest most expensive shingle available

7/16 is fine, but may show some waviness on 24" centres. If that concerns you spend the money on the 19/32 or whatever is available in your market.

 

[earlthegoat2]

Up in MI with snow loads, 24" spacing and 1/2" (15/32) decking with any shingle type or metal was how we built many houses and it had to be to code since it was inscpected. If that is code in AL then the code is overkill, even for hurricanes. Here in SE GA it is the same code as in MI and that is for hurricanes.

 

[seanc_mt]

Having just built my shop. Friend used the same trusses I had built. He used 7/16 osb and his is sketchy to walk on. I used 5/8" osb and its like walking on a solidly built floor. The cost of a 7/16 sheet is $9 something here. 5/8" was $15. my roof took 100 sheets so $500 difference and I know mine will last much longer.

As far as OSB vs plywood there is many schools of thought. Both are not meant to be wet thats why they get ruined. Kept dry both will out last you.

 

[readhead]

There is no structural difference between plywood and OSB. They are interchangeable and I would much rather walk on the rougher surface of OSB on a roof than slick plywood. Most of these preferences are based on old wives tales and go back to OSB's predecessor flake or chip board.

 

[danieldd]

Much appreciated for all your inputs. I will try to address your questions…

TechShield doesn't come in plywood. TechShield has a radiant barrier, this is why I am choosing it to try and reduce the attic temps in the summer. The suggestion of doubling up and adding new decking over existing decking is not a good idea. The radiant barrier would be ineffective and the existing 3/8" decking simply needs to be replaced.

Will it void my warranty? Have no clue, but don't want to be in a situation where it would compromise the warranty.

Shingle type is GAF Architectural. They're the premium type and they are heavier than 3 tab shingles.

I certainly don't want to spend money and cut corners and having a sagging roof a couple of years down the road. It would irritate me to no end if that happened. It appears in this situation to just go ahead and pony up the extra coin (5/8 sheets are $25 each and I need 100 of them. Cost to install is $25, so it will cost me $5000 just to replace the decking as opposed to using 7/16 at $3700).

 

[Falcon67]

My shop is 7/16" Techshield with basic 3 tab 220lb/sq Gray Owens Coring. Rafters are 24" OC. No noticeable issues, roof approaching 6 years in service. I do see some of the vertical seams between the Techshield panels - however, the house uses 7/16" plain OSB at 16" OC I can can see some seams in that too. House was built in 2000, according to the tax assessor records. It has similar basic 3 tab gray shingles on it. Around here we design for frost load LOL. And this year only a couple of days even had that.

 

[yeldogt]

Have you researched Techshield ? Do you have HVAC equipment in the attic?

I'm a plywood guy .. but that's another thread.


With conventional roofing material now pushing a 50 year life -- it's best to do it once ... and correctly. I put 40 year shingles on my house 20 years ago -- they look the same as those on an addition done a few years ago with the same shingle. Roofs are things to do once.

 

[patchap]

Much appreciated for all your inputs. I will try to address your questions…



Will it void my warranty? Have no clue, but don't want to be in a situation where it would compromise the warranty.

Shingle type is GAF Architectural. They're the premium type and they are heavier than 3 tab shingles.

.

Timberline are on the lighter and of the spectrum, Timberline high definition are #225 a square.

 

[Orionrising]

Advantech zip panels are nice.. and waterproof....

Sent from my Moto G (4) using Tapatalk

 

[matt_i]

I'd split the difference and go with 1/2". I'm a plywood guy. Ring shanks hot dipped galvanized

I wouldn't go with 3 tabs, the architectural look better and last longer. Last recommendation I would go with the color-matched extra-thick caps from the same manufacturer. Don't let them save money by cutting up the cheap 3 tabs to make the caps. You would never be able to tell the difference from the street. However, that's what I currently face, the "field" of shingles is perfect but almost every single cap is delaminating.

 

[Falcon67]

With conventional roofing material now pushing a 50 year life -- it's best to do it once ... and correctly. I put 40 year shingles on my house 20 years ago -- they look the same as those on an addition done a few years ago with the same shingle. Roofs are things to do once.

And we put 25 year stuff on ours because it's more than 50/50 that insurance will replace the shingles within their design life. Hail. Big hail. Or wind - clear sky and 50 MPH gusts last Sunday. Did well, only lost one tab on one shingle. I have lived in Texas my entire life and been a home owner since 18 (1974) and have paid outright for one (1) whole house roof, not counting a couple of DIYs on something new like a shed or shop. We've had two houses so far out here in west Texas, moved in 1997. Two roofs on one house in 20 years, only paid deductibles. A "50 year" roof out here is going to be steel.

EDIT - I'll add about steel: we've had one hail storm here that sent down stones that marked concrete and dented asphalt. So even steel can be challenged.

 

[bpjr]

And we put 25 year stuff on ours because it's more than 50/50 that insurance will replace the shingles within their design life. Hail. Big hail. Or wind - clear sky and 50 MPH gusts last Sunday. Did well, only lost one tab on one shingle. I have lived in Texas my entire life and been a home owner since 18 (1974) and have paid outright for one (1) whole house roof, not counting a couple of DIYs on something new like a shed or shop. We've had two houses so far out here in west Texas, moved in 1997. Two roofs on one house in 20 years, only paid deductibles. A "50 year" roof out here is going to be steel.

EDIT - I'll add about steel: we've had one hail storm here that sent down stones that marked concrete and dented asphalt. So even steel can be challenged.

Steel roof prices are coming way down where I live. Last year I replaced a 65 square 3 tab roof with 5v crimp galvalume steel for about 10% more than the tabs. I had 5 quotes and some of them were more for 3 tab than the steel one I contracted for. It also included peel and stick underlayment which beats felt by leap years. This was a straight 6/12 gable with long runs...very little cutting and fitting. 140 mph wind rating. Last year we had a minimal hurricane and no problems like with 3 tabs. Can't say what hail will do but we don't have monster hail here like out west either.

 

[yeldogt]

And we put 25 year stuff on ours because it's more than 50/50 that insurance will replace the shingles within their design life. Hail. Big hail. Or wind - clear sky and 50 MPH gusts last Sunday. Did well, only lost one tab on one shingle. I have lived in Texas my entire life and been a home owner since 18 (1974) and have paid outright for one (1) whole house roof, not counting a couple of DIYs on something new like a shed or shop. We've had two houses so far out here in west Texas, moved in 1997. Two roofs on one house in 20 years, only paid deductibles. A "50 year" roof out here is going to be steel.

EDIT - I'll add about steel: we've had one hail storm here that sent down stones that marked concrete and dented asphalt. So even steel can be challenged.

We don't have hail -- everything needs to be built to local conditions and expected ownership length ... it's especially important today as buyers want homes with no defects. Don't want to have to replace a roof when I go to sell.

I'm surprised insurers have not put in place more special provision regarding hail damage in certain regions. With more development -- some areas are inevitable.

 

[Scott H in Wheaton]

We don't have hail -- everything needs to be built to conditions and expected ownership ... it's especially important today as buyers want home with no defects.

I'm surprised insurers have not put in place more special provision regarding hail damage in certain regions. With more development -- some areas are inevitable.

Insurance companies are starting to change from the traditional old $1000 deductible to a % of home value.
A $400,000 home with a 2% deductible is $8,000
That will discourage some of the storm chasers who try to absorb your deductible to get your business and people who get their roofs changed at the drop of a hat.

 

[kbs2244]

Do I understand you are pulling off the current decking and replacing it?

If so, while they are exposed I would put cross ties between your rafters, on 4 foot centers, before re-decking.
It will help prevent any "sagging."

I much prefer ply to OSB.
Properly aligned, it is much "stiffer."
But you pay for it.

 

[6768rogues]

The heaviest shingles you are considering are not even 4 1/2 lbs. per square foot. 7/16 osb can handle two layers of those.