Decisions decisions, asphalt metal etc

So we bought a house that needs everything. Including a roof.

It is a contemporary, with a tongue and groove 2 inch thick roof system. It currently has an inch of foam insulation. Not in Mass, that won’t do.

So I we are going to do a roof. Obviously Asphalt is the most cost effective on day one. The other advantage is DIY repairs, I mean if a branch dings the roof, I would like to be able to throw a few shingles up to fix it rather than be looking at serious cash.

That said, there seem to be some interesting products out there in the metal roof market.

So, first question:

Pricewise, asphalt is so reasonable, that what is the best shingle for an install over foam? We plan on putting about 3 inches with some CDX. I was planning on putting sleepers for an airspace, but if they will warranty it with no venting, why not So, what is the consensus ‘best’ for this application ?

If I were to go metal , I have to think about whether standing seam is the look I want. If a metal shingle product, what is the most cost effective?

Frankly, I hate buying something that is single source, that might not exist by the time I need some maintenance, or god forbid I want to change something and need to get a small amount of the product to add something or add in a skylight etc.

Anyway, I have a few months to make a decision so am looking for advise.



Not sure if you got prices for asphalt shingles recently or not but they are anything but reasonable.

In the past year they have almost doubled in cost.

Metal on the other hand has more than likely come down due the scrap prices going from $300 a ton to less than $100 a ton.

Don’t know much about metal roofs to answer any of your questions.

Good Luck!!!

For 60-70 dollars a square id go dimensional shingles. Cheaper then metal.

Im not sure where you are buying shingles for 60 a sqaure but tell me so i can have them send over a few trucks.

thank god you have a few months.
make sure you pay your internet bill.
you are going to need us, alot.


Hi Gus,

For the most part, you’ve answered your own questions regarding the various roofing products. Both asphalt and metal can yield a quality roof (Florida notwithstanding). Metal has an advantage in endurance, but asphalt is more readily patched and/or modified especially from a DIY perspective.

Your biggest concern on that contemporary is venting the insulation system. That foam is notorious for trapping moisture against the T&G. This can masquerade as a roof leak, and quickly rot away the deck. If you are getting leaks that don’t coincide with the quantity of rain, chances are pretty good that this is the case.

What’s tough on these is that the insulation is on the topside of the roof deck, so the usual venting solutions would defeat the insulation entirely. One possible solution is to put the insulation under the roof deck , use conventional ventilation practices, and simulate those contemporary cathedrals with t&g and fake beams.

I have not seen any non rain related drips. The only venting issue has to do with heat for the shingles.

I just replaced a roof 2 years ago where there were tabs in the backyard after a wind storm. The part of the house with standard insulation was fine, south and west facing. The part over, in this case 4 inches of foam, the south and south west facing faces were destroyed, north, east facing sides were fine.

The roof on this house is a tan arch shingle, supposedly done in 99, and is toast on the south side.

I am not buying the shingle over foam business unless the company back it up.
As I said, asphalt is reasonable, so I guess it is down to what product will the manufacturer stand behind over a unvented roof?

I would love to have that extra 3/4 for insulation.

metal is junk. condensation, paint fading, retightening leaky screws and denting. that is no good. If you are planning on living there for a long time get a nice lifetime shingle and be done with it. If you have 3 inches of air space that is plenty for bucket vents or ridge vent any of my reps would warrenty that. just be sure to vent soffit to create air movement. Cetainteed, GAF, Owens Corning and Malarky all make excellent lifetime shingles. I personally like the presidential shake style myself. Just be sure to hire a liscenced and insured contractor not some scabb.

You misread, I plan on 3 inches of foam. There is no airspace now. I was planning on doing what I did on my current[similar style] roof, lay down strapping and another sheet of plywood, creating a 3/4 inch air space. If the manufacturer will warranty without it, I would rather have the additional insulation.This is all above the foam.

Gus, look into a decra roofing system. It is a aluminum zinc alloy coated with steel granules. They type im talking about looks like actual shingles. 50 year warranty and blah blah blah. I know our price is about double for material and labor than a 30 year shingle but if you have the money look into it. Another good thing is that it is a “green” product, meaning it is recycable after the years it spends on your roof and a percentage of it is made from recycable materials.

I suggest you look into it, you might be pleased. I have been starting to sell some of those type jobs up here.

actually had emailed for info on that one

how do you find it for install?

Gus insulation is good but air flow is better. If you have 3/4 air space with adequate roof and soffit vents you should be alright. I would check with tech support first but all roofs have to breathe to achieve maximum lifespan.

Insulation is equally important, without it you will just be venting all the heat from the house through your roof.
Ventilation is a system in which all components of the system must be properly installed.

That would be the way. check into the premade product. It has the foam/iso board attached to your choice of osb or plywood with the air gap. It takes an expert to make one on site. Doable, not for the novice.

No offense, but i’ve already done it once, on an 8 sided hip roof no less, thus my wanting to avoid it again if possible. The premade product I have found doesn’t come the way I want it and is nothing special that I can see.

No offense taken. I wasn’t aware that you have done that before.

How much insulation do you need to achieve an R 30 value?

Well, if you use iso board, 3 inches is r18, 2 inches of wood get another 2 1/2. I am planning on increasing the facia from the current 5 1/2 to 7 1/4 and reducing the amount of overhang. If I do it like this:

1/2 cdx
3/4 strapping
3 inches foam
2 1/4 actual dim wood[have to check, this is the floor thickness, roof could be different]

that leaves me with 3/4 vertical overhang below the wood on the underside of the roof, should be enough to keep the drips from running up the underside.

As you can see, I would love that 3/4 of insulation, but the south side is already dead after [supposedly] 9 years.

Various metal products may allow me to get more foam in.

Gus go to the decra website at

If memory serves me right it will tell you where and how to find installers in your area. Of course if you live more up north it is harder to find people who know how to do it compared to down south since it is much more rare in the north.

you know, I went there and posted a question to them, I better try again because I got no reply.

Gus, you probably won’t get a reply from decra, as they are horrible when it comes to that type of thing…

Anyway. I believe you can use that 3/4 for insulation purposes which would give you extra 4.5 r… This can be achieved with a metal roof - Standing seam or shingles (my preference is aluminum shingles).

You would have to use a synthetic underlayment and the only one we use is GAF DeckArmor. It is breathable, so condensation forming under it would be venter to the outer surface. It will also keep the roof watertight by itself, so the condensation from between metal and underlay wont go inside your home.

You can get a square or two of extra materials and some coil stock in case you decide to “get a skylight” or something like it in the future.

With standing seam it is not as easy, because panels have to be certain length, and you dont want to get a 100 ft of extra panel in one piece. On the other hand, Snap Lock standing seam is pretty universal, and can be acquired from any metal roofing shop - just get the right color.

In any case, shingles are more versatile, easier to work with, cheaper than Snap Lock and also provide concealed fasteners install.

I do not recommend any sort of corrugated steel type of pane with exposed fasteners - this crap is for farms, barns, etc - not for a contemporary house.

I also recommend Aluminum, as any metal roof will “sweat” - there will be condensation on the underside, and it won’t affect aluminum, while steel may rust, if it was scratched during installation, which happens all the time to standing seam roofs. Steel Shingles are slightly different, as they are packaged with a thick brown paper between each shingle, and you take them out of the box 1 by 1… so scratches usually appear on the outside, where they are usually not deep, and the galvanizing coating is usually not even exposed.

Here is a question - why no increase the total thickness of roofing assembly? Why can’t you get a wider fascia board? like a 10x1 plank? that will giceyou almost 2 extra inches…