Roofing Question - Re-Roofing my Home

[SJay]

Any roofers want to chime in on what is the best way to re-roof my home. I will explain what is there currently. Photo below would be the inside (not my actual home). . When I bought our house the interior ceiling looked similar to the picture. We framed in the ceiling and dry walled it and then pumped it full of cellulose insulation. Now the question. I have 2 layers of shingles, 1 layer of 1/2" celotex, felt paper and then the pine tongue and groove you see in the pictures. I plan on tearing everything off except the pine (that is my interior ceiling). Do I need to put the 1/2" celotex back down and then felt paper and then the shingles or can I skip the celotex and put the felt paper on top of the pine and then install my shingles.

Thanks

 

[RNeumann]

The question is more of an insulation, ventilation and building envelope question. You don't say how the ceiling was framed or how much insulation is used. You also say the T&G was covered and then you say it's the ceiling.

Assuming the T&G is covered by framing, cellulose and drywall-

The ceiling insulation recommendation is an easy find. Google recommended insulation by region. The USA has about 7 climate zones and also recommends insulation based on those zones. If you have enough cellulose skip the Celotex. If you still want more insulation consider some added rigid insulation on top of the T&G.
My bigger concern is the venting. The space between the top of the cellulose and the bottom of the T&G should have some air movement. A ridge vent and some holes at the eves would work best. You will get moisture in there (impossible not to) and without venting you are asking for trouble.

Bottom line- skip the Celotex and add venting. You should be good to go- assuming everything to that point was done correctly.

 

[mbohuntr]

That COULD be SIPS or Structural Insulated Panels... I would either look up the original builder, or talk to a knowledgable person on them before I started ripping... you could end up needing to replace rather than repair the roof if you damage it.

 

[Zerk]

That COULD be SIPS or Structural Insulated Panels... I would either look up the original builder, or talk to a knowledgable person on them before I started ripping... you could end up needing to replace rather than repair the roof if you damage it.

I was wondering, what up there. Not strutural, but I think they do an extra layer, because there is no venting in this type of framing?? I speaking from my bowels, and probably full of it.


But I have wanted to add room with rafters so I could go high ceilings.

 

[mbohuntr]

Dunno... I haven't seen a build like that before... i'm just worried about making it worse before you understand it.. venting sounds right, but i'm no expert.

 

[breadtrk]

Screw in purlins and put a metal roof on it, leaving the old stuff. Metal roof is naturally vented, lasts almost forever, comes in almost any color you can imagine, is cheaper than a tear off and new everything else, and you keep any insulation properties already up there.

 

[Raspy]

On exposed T&G ceilings/roofs like yours, the insulation must be on the outside. Thus, the Celotex under the shingles. Since you insulated and added a ceiling, you don't need the Celotex outside. And since there are already two roofs, you have to do a tear off.

The Celotex and shingles setup is subject to moisture damage and it's not very strong in high winds unless there were sleepers screwed down, the Celotex added between them and then a layer of OSB went down to accept the roofing nails. If you only have the T&G deck up there, get rid of all the old insulation board and the two roofs. If you want more insulation than you currently have, add sleepers and fill in with insulation board and then a layer of OSB to accept the new roof. Blue Board or Pink Board styrofoam is better than Celotex because it does not absorb moisture. Check with local codes to see if a fireproof board is required.

Once you figure out how to vent the space created below the T&G, and the added insulation system on top, if any, you can either roof directly over the T&G and have a strong system, or roof over the OSB and have a strong system with added insulation. As previously mentioned, a steel roof might solve everything at once. Plus it will last a lifetime and is fireproof.

 

[MossRoad]

My father had a roof almost exactly like that on the house he built. It was Douglas Fir. No insulation under it. Exposed like that picture. It had three layers of felt, tar paper, felt, tar paper, felt, tar paper, then tar and pea gravel. No insulation, as, at the time, "natural gas was almost free" he would say.

In later years, well, natural gas was NOT free, so he had the gravel, and the layers of tar paper and felt removed, new tar paper and felt, then 2" of foam insulation, rubber ice dam material over that, then shingles. I do not know how they fastened the shingles through the 2" foam but I'm guess LONG NAILS into the doug fir, but I'm not sure. :confused3:

His other choice of insulating would have been what you did, which would be to fill in between the rafters with insulation, allowing for air movement on the underside of the un-insulated planking, and boxing it in. He wanted to preserve the plank look, so that's why he went with the insulation on the outer side. It was also much less work and no venting was required.

It's still there 37 years later, so it must have worked.

 

[MossRoad]

My father had a roof almost exactly like that on the house he built. It was Douglas Fir. No insulation under it. Exposed like that picture. It had three layers of felt, tar paper, felt, tar paper, felt, tar paper, then tar and pea gravel. No insulation, as, at the time, "natural gas was almost free" he would say.

In later years, well, natural gas was NOT free, so he had the gravel, and the layers of tar paper and felt removed, new tar paper and felt, then 2" of foam insulation, rubber ice dam material over that, then shingles. I do not know how they fastened the shingles through the 2" foam but I'm guess LONG NAILS into the doug fir, but I'm not sure. :confused3:

His other choice of insulating would have been what you did, which would be to fill in between the rafters with insulation, allowing for air movement on the underside of the un-insulated planking, and boxing it in. He wanted to preserve the plank look, so that's why he went with the insulation on the outer side. It was also much less work and no venting was required.

It's still there 37 years later, so it must have worked.

As Raspy suggested, maybe he had wood sheeting placed over the foam. I don't know, as I wasn't there on roofing day.

 

[oosik]

Well, if I read your post correctly - by framing in the ceiling, enclosing it with dry wall and then pumping it full of insulation - you now have a certain amount of insulation "inside" the house. I would only strip off the shingles if they were bad - in other words, put a third layer of new shingles right on top of what you already have. If you have bad shingles and want to rip it all off, down to the pine boards, I would put down one layer of felt paper, over the boards, before you nail down a new layer of shingles.

You could also build the "outside" roof up - just like it is now - if you wanted additional insulation value. Its up to you.

I have an exposed beam ceiling with all the insulation on the outside/top of the roof. Been there 35+ years and is still doing just fine.