Cathedral ceiling roof low slope


I am in the process of having a roof replaced. The house is in Oklahoma, constructed in 1965, roof/ceiling has slope of 2.5, and is supported by 4x12 cedar beams which are spaced approximately 6.5ft on center. Currently has tar and gravel roof in which some idiot went directly over with asphalt shingles. I have one section of the ceiling that is sagging due to a previous owner cutting two 8” holes for a large hood vent and weakening the decking. The ceiling appears to some sort of hollow core material that serves as the ceiling face AND the roof decking. The best way I can describe it is that it looks like a hollow core door. The pictures attached Are where I have peeled this decking off. (I didn’t realize the ceiling was also the roof decking!..I currently have it supported from below) Previous owner went over the ceiling with texture.
Can anyone recommend a product similar to what is currently on the roof? None of the 6 roofers I have had look at this have been able to identify a solution to this.
When I reroof this I would also like to add some sort of

insulated nail board as there is currently no insulation on the roof. I then plan on installing ice and water shield with Owen Corning duration shingles. I entertained the idea of a metal roof but this roof is about 115 squares and metal just doesn’t fit into the budget… any info or advice you guys could provide would be greatly appreciated! Thanks!



Do not use owens corning durations on that 2.5
No matter what.
Absolutely the worst Architectual shingle for a low slope.
Use Atlas pinnacle Only! No exceptions!!
Okay, Malarkey if they are available in your market. But their material cost significantly more
Especially if you want the roof to remain stain free parterned with 3m Scotchgaurd.( like Atlas)
I would only use Malarkeys Legacy line.
If you absolutely cant get them
then use Low-slope roofing only like Certainteed Flintlastic.
I could write a book here with photos, i dont really want to take the time today.

Durations trap and collect water.
Water sits in their nailing area and rots out the fasteners/penetrations.
It is a bad design.
I wanted to love them also.
I used them many times.
I learned not to.

Atlas and Malarkey are supremely superior in two ways.
First , they have taken extreme actions for their shingles to remain good looking beyond 5 years
By partnering with 3m Scotchguard.
The only shingle manufacturers to do so.
Second and even more important is they out designed every one else by making a proper nailing area.
A nailing area where the roofer is not installing the nail too low or too high.
They have the only proper nailing zones.
This is super important on your 2.5 slope.
Until Atlas started making these shingles…
I would never dream of installing Architects on a 2.5 slope even with Full ice and water shield.



Thanks for the input. I’ll definitely research the shingles you mentioned. Every roofer so far has pitched the duration. Real common shingles around here but a 2.5 pitch is very uncommon and I can tell most of these roofers haven’t dealt with many low slopes like mine.
I know the picture I attached isn’t the best, but can tell what the material is making up the ceiling/roof deck? Reading through all the discussions I’ve seen you mention homosote a few times. Do you think that’s what mine could be?



Homosote was my first reaction for your style of house.
But your pictures prove it is not.
Homosote is a solid material, not hollow.
A 2 foot by 8 foot tounge and groove material.
I wish i could help.
I havent seen that product before.
God bless your search!
Go to the oldest, real roofing supply house in your area and Maybe they can help you.

Homosote is hard to find and i cant remember if it is 2 inches thick or two and a half inches thick.
It might be able to substitute this product if you need it.
It just looks like the total thickness of your existing product is a little thicker.
It might be just right though.



If your going to cover the whole thing in ice and water, you should also cover the ice and water with felt or synthetic.
If your using standard ice and water, the shingles will stick to it. When you need to reroof again, you would need to replace all the sheathing to get a reasonable surface, or plan on days and days of scraping.

Minimum hot dipped nails, stainless if possible on that pitch.



Patchup is right.
It makes the tear off twice as hard with all the additional scraping involved.
Ive done it a couple times now and it didnt hold us back Too terribly.
About the same amount of time as removing a second layer of shingles…
Much easier to remove while not hot…

But yeah, i do like the idea of putting a cheap synthetic on top sparingly nailed to spare the next roofers Heart and Back.

Im sure ihavent met the IW from hell though
Like GAF weather watch??
You dont want to use that stuff if possible
To install or have to remove from.
Its a goowy mess.



Your ceiling/roof is Tectum Roof Deck. Heavily used during the WW2 period due to shortage of wood sheathing. It is still made but pretty hard to find. Call the company. If that is what you have, you probably have to do some extensive reconstruction of the roof if you can replace it in kind. For Gods sake, don’t recover over it with comp.



Thanks for the info! I’ll look into tectum. What would you recommend if you don’t think I should use comp? Metal? I’m still trying to decide the best route to go with this. Never realized there was so much to consider with roofing before this project…



I dont know if your neighborhood allows it, but what about Sheet Metal? The low pitch concerns me. I’m guessing the old built up with gravel weighed about 5lbs a sq. Ft. Maybe more. Metal panel is about 1lb a foot. Your home style might not fit a metal roof, but I’m just throwing it out there.



I appreciate everyone’s input. You guys are really helping me out a lot. I can’t get over how little the roofers around here know about roofs. They all just want to rip of the old, slap on some new, and take my money. There’s a lot more to consider with this roof as it’s kind of a unique situation. Glad I found this forum!

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Rooferama we are considering metal as an option. I still want to remove all the old tar and gravel though. There is no HOA so I’m free to do what I want. It’s a massive roof though so I’m not sure metal is gonna be affordable.



Reached out to tectrum and homosote companies and sent them pictures of what I have. They both said it’s not their product… back to square one.



That looks like it is made similar to a SIPS panel but without the insulation and the small wood for support. How thick is the top layer of wood? If it is a 1/2" or greater you can use a vented nailbase over the deck and install ice & water and shingles or metal over it. You can also consider installing EPDM, PVC , or TPO with a layer of ISO insulation. If the top layer of wood is less than 7/16 you can still do that but no manufacturer will warrant it. Only exception might be using insulation adhesive and adhering the nailbase or ISO if you can get a good pull out on the adhesive. All of these options will be expensive though compared to normal shingle roofs.



Through my research I found SIPS. It does look like a ‘hollow’ version of those. Believe it or not that panel is not even 1.5” thick. Both sides of it are made of just a wood veneer about 1/8” thick with a 1” hollow core in the middle. The total thickness is about 1-3/8”. It is 3’ long and the ends appear to be tongue and groove. On top of that there is a black 1/2” fiberboard, then the tar and gravel roof, then shingles. I’m surprised a thin hollow core panel like that has held up all that weight for this long…



SIPS are surprisingly strong and this is likely the same. Your only real option is going to be using some kind of adhered roof. If it is residence you can’t get better than a membrane only warranty for most commercial roof products. I would recommend finding a commercial contractor in your area and see if they can take on the project. You can adhered a fleeceback membrane directly to the panel if you are ok with no insulation, or you can adhere a layer of polyiso and EPDM or TPO. I would recommend EPDM personally in this case since TPO can have problems with condensation in the winter.



Good idea on that Dtris. I would add a vapor barrier as well. I would chose my membrane based on a wind (TPO) versus falling branches (EPDM) criteria. If TPO is the choice I would recommend Gray over White. Dirty gray looks better then dirty white to me.



Why don’t you just put EPDM on it



Turns out they used actual hollow core doors for the roof decking. On top of that were 2 layers of tar a gravel, each layer having a 1/2” piece of fiberboard. Then shingles over that…
The doors are all bowed a little but in good shape considering they’ve been up there for 50 yrs. The cedar beams on the roof are even spaced exactly 80” apart, which is the night of a hollow core door. It’s like they planned to use doors for the decking from the beginning of construction…
Just wanted to give you all an update. I can’t imagine that anyone else has heard of a situation like this before. I appreciate everyone’s input.



I’m going out on a limb here, but alcohol, had to be involved in that decision. I’m guessing the hard stuff.