Roofing questions - going with a metal roof (1 Viewer)

[alia176]

Hiya folks,

I'm going to a metal roof from shingles and wanted to verify some things that I've been hearing from the roofing companies. I have the original single layer of shingles that have seen many years of hail and wind damage. Three companies came and gave me estimates. My ins companies cut me a check for slightly under $10k for 26 squares. A square is 100 sq ft, I learned.

Anyway, two out of the three roofers gave me estimates for a total removal of the old shingles and a fresh install of a new roof. Of course the metal roof increases the cost by quite a bit. The third guy says why strip? Just lay down the new metal roof on top of the old one and that'll save me about $2k and of course a load of time.

My rain gutters were made by ABC seamless and they're badass. The PO had them installed and he spent a pretty fortune on them for onsite manufacturing. I had them come out to give me a quote of detaching them from the roof, then re-attach them after the new roof went on. He didn't have to give me an estimate after he took a look. "yup, it'll be about $2k for my guys come out and do their work". At this point, I shat my pants He says to me "why remove the 1st layter, just lay over the 1st layer and don't touch the gutters". Hmm, I like that idea.

So, I'm thinking about going with the third guy , Roofer C, who will simply lay down the new metal roof over the single layer of shingles, will not touch my gutters. He will have to cut slots in the drip edge so they go around the gutter stays and into the gutters. He is a local company, been around for many years but thinking of retiring. He gave me 1 yr warr on labor and 30 years on the metal roof. This guy might also do other projects at my house like hang up the siding with a flat cost of $1600/day for four workers.

I went to the two metal roofing supplies in town and get an estimate of material cost.

Metal mart
-exposed fasteners, burgandy color, all fastenrers, drip edges, trim pieces, flashing for vent pipes - $7074
Metal center
- " " " " " - $6840

Roofer A
- shingles cost $14,211, Metal cost $24,557
Roofer B
- shingles cost $11,880, Metal cost $16,100
Roofer C
- metal cost $ 17k (didn't like the idea of me buying materials but he doesn't mark up either. Passes me the receipts.)

Any gotchas or shenanigans this industry pulls on unsuspecting home owners?

cathedral ceiling over the living room

 

[kirvesmies]

@alia176 , ask local suppliers what they are hearing regarding the contractors. also they should be able tell you where they've dropped material. get a couple of addresses n go n talk to them. if you have friends in the building industry, quiz them.
now, regarding metal roof right on the shingles, i don't like that form of install because you are running your fasteners only into plywood. if the plywood is compromised by water intrusion, the grip strength is gone leading to blow off in strong winds. i'd strap the roof over top the shingles with 4 or 5/4x4 fastened to the rafters/trusses. you didn't say what style of metal roofing so the above advice pertains to corrugated metal roofing and some shingle style metal roofing panels. main thing is do your due diligence in vetting your contractor.

 

[KLF]

I personally would want to see the sheathing, and get a fresh layer of Grace (ice & water shield) on the eaves and valleys, and new underlayment.

I like the idea of the strapping. Vented rain screen is always good.

 

[e9999]

I'm pleasantly surprised that your insurance company would cover that if it was progressive damage. Nice.
Any issue with weight if you keep the shingles on under the metal?
You're a DIY guy. Thought about removing the shingles yourself to save $$? Should not be hard.

 

[Mauser]

I installed quite a few metal roofs in a former life. The only argurment I have against going over the shingles is that the underside of the metal will be scratched by the gravel on the shingles, there will be condensation that builds up under the metal and could cause rusting from underneath. I have never seen it happen though. This problem could be solved by putting a layer of 15# felt down in between the shingles and metal.

Couple of benefits of going over the shinglea are the added insulation and sound deadening.

 

[Rugy]

Not all metal for roofing is the same.
What gauge of roof are they providing ?
We only use 22g or 24 gauge.
No exposed fasteners.
All screws and clips are out of stainless steel.
Underlayment is a peel and stick made by Protecto Jiffy Seal Ice and water guard ht 250 40m.
Between the metal and the Protecto we use Enkamat or delta drainmat. This allows the underside of the metal to breathe.
Also metal will condensate on the underside of the metal, drainmat will allow water to drain or evaporate.
Leaving the old roofing shingles will make the metal roof not as noisy than the 15lbs non perforated roofing felt.
But have never had a client complain about the metal roof rain noise with Enkamat or Delta drain mat.
Not putting a breather system under the metal or directly on the "sandpaper" duroid with the rock granules will scratch the sh*t the underside of the roof and it will rust, guaranteed.
Gutters, remove them yourself. Install them so that the outside edge of the gutter is 1" lower then the line of the sheetmetal.
What I mean is take a 1x2 x24" of wood, place it on the metal roof, allow 1x2 to project 6 to 8 inches beyond roof line. Install gutter one inch lower that the line of the 1x2 projecting. This way if you ever have any accumulation of snow on the roof, the snow when it slides off the roof it wont rip of your gutters.
Snow break installation is good but more money. Install snow breaks over door way entries, no snow slides off the roof over people coming or going.
My 3 cents.
Good luck with your project.

 

[e9999]

^ they probably don't have as much snow or rain in NM than they do in BC, so some of that could be less of a concern?

 

[MrMikeyG]

I worry about getting a nice flat and true install (I know we're not talking floors here) by installing over old asphalt comp versus nice fresh ice and water shield or whatever the equivalent is for NM. In a rambler, I would strip the old myself any day of the week. If you're 2-3 stories with a bunch of dormers and other complications, I would probably have someone do it.
Have you been in your attic recently? That could give you an idea of the health of the roof sheathing. I really don't know what to suggest as far as the gutters, it does look like they installed with screws and clips, that makes removal a lot easier.

 

[alia176]

Thank you gents for your awesome replies. It has been quite educational. Let me answer some questions that were presented:

- 26 gauge seems to be the norm around here.
- exposed fasteners vs concealed seem to be an aesthetic thing, from what I can tell.
- I have no roof leaks as I have access to the second story attic. First story is vaulted ceiling using 2x10 rafters and a giant glue-lam ridge beam.
- regarding screwing into plywood

@kirvesmies
now, regarding metal roof right on the shingles, i don't like that form of install because you are running your fasteners only into plywood. if the plywood is compromised by water intrusion, the grip strength is gone leading to blow off in strong winds. i'd strap the roof over top the shingles with 4 or 5/4x4 fastened to the rafters/trusses. you didn't say what style of metal roofing so the above advice pertains to corrugated metal roofing and some shingle style metal roofing panels. main thing is do your due diligence in vetting your contractor.

This is an interesting point. If the roofer were to remove the shingles, would they be screwing the corrugated metal roof directly onto the rafters or to the plywood? If they lay the metal on top of the shingles, they'd not have an easy to detect the rafters.

High winds is an issue at my house as I live on top of a ridge and updrafts can be quite strong.

-point taken about scratching up under the metal and laying down felt/composite underlayment will alleviate that.

-can I remove my own shingles? Yes.
Do I want to? - nope. Monsoon season is upon us so the timing would have to be right between the removal and installation. Do I want to bend down and pick up every single shingle off the ground around the property? Nope.
I live on a ridge top and the winds up here is strong. So, the lighter shingles will fly many feet away from the house and I'd have to go hiking through my property, picking up shingles. Doesn't sound fun to me!
Do I want to run a large magnet on wheels all around my property, going over bushes and native soil? NOPE. I don't live in a concrete jungle

Updated the first post with the blueprints to my house for ease of clarity and scope of project. I should've done that in the first place. The knowledgebase in this section of mud is quite astounding.

Thank you and keep them coming please. I haven't agreed to any of the quotes and want to make sure I ask the right questions before committing.

 

[alia176]

Gents,
Please help me understand where this water marking is from. The picture is looking up at the cathedral ceiling of my living room. As you can see, water marks are present where the sheetrock meets up with the glue-lam ridge beam.

Could it be that my attic space is forming condensation and hitting the ceiling sheetrock? This isn't fresh but it's been up there since I bought the house 15 years ago. There are no ridge vent in this space and the markings are present on both sides of the ridge beam. This is a 2x10 construction so no attic space to speak of.

Roofer C suggested that I put a ridge beam on this part of the roof to eliminate condensation. He didn't come inside the house and see this issue but he did bring up a good point.

Non vented ridge (left) is over the living room cathedral ceiling.

Here's the soffit that is part of the cathedral ceiling.

 

[KLF]

I would ABSOLUTELY have a ridge vent installed (I think that is what you meant). I can't imagine any reason to build a roof over a moisture-laden living space without a ridge vent. Here's what can happen if the roof isn't properly vented (photo from Fine Homebuilding article that I used in my classes, this is above a cathedral ceiling).

 

[kirvesmies]

you asked would they fasten new roofing to rafters if shingles were stripped, it can be done but i'd fire my roofer if he tried that game. roof framing members on your house would be 16" o.c. i'm assuming stick frame roof vs trusses.

 

[kirvesmies]

I would ABSOLUTELY have a ridge vent installed (I think that is what you meant). I can't imagine any reason to build a roof over a moisture-laden living space without a ridge vent. Here's what can happen if the roof isn't properly vented (photo from Fine Homebuilding article that I used in my classes, this is above a cathedral ceiling).

View attachment 2743886

@KLF , i'm going to go with other factors assisting that $h!t. like vapor barrier on heated side poorly done or nonexistent . to properly vent a cathedral ceiling, every rafter cavity should have open from soffit to ridge a 2" space between between insulation and underside of roof decking. that 2" is in the building code i deal with. when i frame a cathedral roof, i actually build that space in before insulation is done

 

[kirvesmies]

@alia176 , that water marking could be caused by vapor barrier not sealed to the beam. in my pertinent building code, i have to actually caulk that.

 

[DBULL]

I went through this about two years ago. I decided against a metal roof for the appearance and type of installation.My understanding is that if exposed screws are used they have to be replaced every ten years or so.At any rate ,after several estimates I went back with architectural shingles for $8800 including a tear off on a 3000 sq/ft home.

 

[KLF]

you asked would they fasten new roofing to rafters if shingles were stripped, it can be done but i'd fire my roofer if he tried that game. roof framing members on your house would be 16" o.c. i'm assuming stick frame roof vs trusses.

Interesting. I haven't built a ton of roofs, but every one I've been on has been 24" spacing. My entire house is stick framed and it is 24", and I just set trusses on a new house 2 weeks ago and they are also 24" spacing. This is in snow country, 60 psf design load. Maybe it's different where you are.

@KLF , i'm going to go with other factors assisting that $h!t. like vapor barrier on heated side poorly done or nonexistent . to properly vent a cathedral ceiling, every rafter cavity should have open from soffit to ridge a 2" space between between insulation and underside of roof decking. that 2" is in the building code i deal with. when i frame a cathedral roof, i actually build that space in before insulation is done

Here is the article, yes this is an extreme case, but it does point out how you need to be careful with moisture and venting, especially with a cathedral roof, which I also have on my house.

5 years ago I used a FLIR and discovered that all the crappy fiberglass fell down in my rafters, I had about 4' of uninsulated ceiling. So, all the sheathing came off, I tossed the fiberglass and those stupid foam baffles (HATE those things) and installed 2 layers of 3.5" polyiso insulation, which left 2" of air gap. Then new Zip sheathing and shingles.

Can you tell I hate fiberglass?

 

[MrMikeyG]

For you guys in snow country and running trusses, what are your bottom cords on the trusses?
I have very minimal personal experience with spray foam so far, but isn't that one way to get by without venting a roof? I think the foam only counts as a thermal break, so you would still need moisture barrier.
In that picture from the OP, I wonder if there is just condensation on the interior surface that has "wicked" onto the beam?

 

[kirvesmies]

Interesting. I haven't built a ton of roofs, but every one I've been on has been 24" spacing. My entire house is stick framed and it is 24", and I just set trusses on a new house 2 weeks ago and they are also 24" spacing. This is in snow country, 60 psf design load. Maybe it's different where you are.


Here is the article, yes this is an extreme case, but it does point out how you need to be careful with moisture and venting, especially with a cathedral roof, which I also have on my house.

5 years ago I used a FLIR and discovered that all the crappy fiberglass fell down in my rafters, I had about 4' of uninsulated ceiling. So, all the sheathing came off, I tossed the fiberglass and those stupid foam baffles (HATE those things) and installed 2 layers of 3.5" polyiso insulation, which left 2" of air gap. Then new Zip sheathing and shingles.

Can you tell I hate fiberglass?

span and material used as you know makes a difference. trusses on average are 24" o.c. as the strength is built into the design. if i recall correctly, we are right in around the 60psf
yeah, i'm not fond of fiberglass either. agreed on the foam baffles also

 

[kirvesmies]

For you guys in snow country and running trusses, what are your bottom cords on the trusses?
I have very minimal personal experience with spray foam so far, but isn't that one way to get by without venting a roof? I think the foam only counts as a thermal break, so you would still need moisture barrier.
In that picture from the OP, I wonder if there is just condensation on the interior surface that has "wicked" onto the beam?

bottom chord depends a number of things. i've handled trusses with anything from 2x4 to 2x10 bottom chords
re: roof venting . don't skip on it. i put metal on my shop last fall. it covered the original shingles from when i built it, 20 years ago. yup, i got 20 years out of 10 year shingles. every truss cavity was done like i mentioned in the earlier post.
open cell foam needs vapor barrier. closed cell does not. we vapor barrier every thing

 

[Rugy]

Any screws for sheet metal roofing must penetrate and extend through the plywood at least 3/4 inch. Per RCABC .
Ridge vent is a must for a cathedral ceiling as others have chimed in if you are using fibreglass or Roxul insulation
Spray foam if installed properly is very effective. Fill the underside of the roof between the roof rafters or trusses.
Options of spray foam are closed cell vs open cell. Open cell foam will require a vapour barrier. Poly or a vapour approved spray paint
Another option is an inverted roof. This is the best option in my opinion.

Trusses are build per roofing material used, snow loads, seizmic concerns and spans.
So they will be build according to needs for each application.