Hi Everybody,
I am going to build myself a new house and I would like to have exposed rafters with a T&G pine ceiling in some part of it, but I am puzzled by how to insulate it properly (R-30 at least). I could go for SIPs, but they are pricey. Or I could create another structure above the T&G with 2 x12s and insulation in between, but that seem very redundant. I see this done many places (pictures) but I have not been able to find any proper details. Any suggestions?
Henrik13
Replies
sips ontop of timberframe, now that's pricey!
My suggestion:
Framed ceiling / roof as typical with insulation. It needs to contain "baffles" for airflow from soffit to ridge vent above the insulation. Baffles are styryofoam egg carton looking pieces, which are sized to fit the rafter spacing and 4' long. They create an airflow channel above the insulation.
Install a decorative wood ceiling under the rafters and install false beams or rafters. This can be done at trim phase.
Edited 3/16/2007 1:33 pm ET by txlandlord
Henrick13
SIP's on top of timberframe.. not as spending as you'd believe.. SIP's depending on your location will cost around $3.50 to 4.00 a sq.ft. (unless you go through a broker or allow the contractor to mark up materials)
Timberframe can be had for as little as 40 cents per bd.ft. a 6x9 timber could cost as little as $1.80 a foot.. White oak is a bit more at $3.24 per foot. ash or other woods will be around. $2.70 foot.
So an 18 foot long white oak timber will cost $58.32.
You will be exrtremely happy with SIP's they are very energy efficent and close in very quickly..
Other options include spraying foam into the bay of a stick framed ceiling. Celluliose and fiberglass the latter two are not my insulations of choice..
your prices will vary, objects in the mirror are closer than they appear, close cover before striking..
Thank you for the input. Appreciate it!
Frenchy, how's it goin'?
You might want to give him the inside story on joining and sealing those panels on the roof so moisture doesn't become a problem he'll be coming here later to solve.
I know that you have a very good idea of certain aspects of this type of frame.
thanks.
Hey, donate a knife sharpener to John T8's sisters collection to send to some Marines on duty in the M.E. You can find the thread in the Tools folder. I'll post a link if you need it.A great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Calvin
The "trick" is exactly what the manuals refer to. You need to put a layer of poly as a vapor barrier between the sheetrock (or whatever ceiling material you use) and the panels. Other wise as we saw earlier vapor pressure will force vapor up between the gapin the panels and cause problems..
The other "trick" is to put the panels in horizontal rather than vertical. That way the weight will compress whatever adhesive you use and do a better job of sealing. In addition once you have the first panel in place that will hold and help align all the subsiquent panels and make their installation much, much, easier. I found out that trick half way thru my home and if I'd had it earlier I would have cut about 1/2 of the time I spent installing the panels..
Where are you? In the Pacific Northwest one common way of dealing with that is 4" of rigid insulation over an 1 1/2" t and g ceiling, with the exposed rafters being at 4'-0" o.c. The plywood is nailed or screwed through the insulation to the decking. 4" of rigid isn't enough in most climates, but you have to take into account that with no framing to create thermal bridges, it is a pretty efficient 4" of continuous insulation.
Edited 3/19/2007 11:57 pm ET by fingersandtoes
I'm in Central PA and I am looking for an R-value of 35-40. I have thought of doing what you are suggesting, but with 5" of rigid polyurethane sheets (I think it is also called poly-Iso) and with 2 x 6 purlins on edge @ 4' OC to nail to roof to. Supposedly it has an R-value of 7-8 per inch. Haven't priced it yet though. 1 1/2" T & G ceiling (I assume that is what is the deck you refer to)seems very heavy duty. Is that because of the 4' OC of the rafters? I s that readily available? Thank you for your input
The 2" x 6" t and g is what is used around here on most post and beam roofs. You can span 5-0" with it as a roof deck, so the ceiling structure takes on a look that is more beam-like than joist-like. The 1 1/2" depth means you can eliminate the purlins and nail the roof sheathing directly to it through the insulation. It also makes overhangs at gable ends easy, as it can cantilever out without additional framing. Here on Vancouver Island the lumber yards stock it in cedar or hemlock, but sawmills do fir and alder as well.
Thanks,
The only problem I see with this system is that it will be hard to get enough insulation on it and still attach the roof properly. But thank you for the idea.
Put the plywood down onto the rigid and lay the screws to it. That part couldn't be simpler.
Yes, but how do I get R-30 minimum?
Henrik,
I have done re-roofs over T&G decks and added insulation when I did it.
I put a 2 x 6 (on edge) frame up around the perimeter.
Then lay 2 x 6 on edge every 4 ft oc. up the roof fastened to the existing roof deck with Simpson angle clips screwed both into the new sleeper and the existing deck.
Fill the 4' space with a layer of 2 1/2 " ridgid followed by a layer of 3 " ridgid. 5/8" ply over everything then metal roofing for the finish roof.
Depending on the r value of your foam you can get R-25 pretty easily.
Thank you.
This is the exact detail I have come up with myself. Simpson makes a clip (RTR) that will work well for this condition.
One question: Why would I use plywood between the 2x6s and the metal roofing. Is that to get something to screw the roofing to in between the 2x6s that are 4 feet apart? Or some other reason?
I did that just to provide the extra fastening surface. The metal roof I used was a standing seam, installed by a sub-contractor and he wanted the ply so I obliged him.
The other choice was to add more sleepers at closer centers and I wanted to not do that .
One additional reason was I was adding an addition out one end of the existing building and the original roof was badly built (not equal pitches both sides, but not intentionally so ) and the plywood helped me "float " the transition between the stick built and my truss built roofs.
Here's some pics of our roof. It's known as a 'cold roof' in our area. IRRC, the schedule is:
rafters, pine T & G, peel & stick R & I shield, 2x10 sleepers on edge with 9" of foam between (R 36), straps, more R & I shield in valleys, felt, steel.
Scott.
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Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Edited 3/28/2007 2:32 pm by Scott
Scott - Why the R & I shield on the T & G? Are you using it to stop moist air from migrating up through from the interior, or as a safety net for water that has penetrated the roof?
Looks like a nice place.
>>>Why the R & I shield on the T & G?Yes, you're right. The layer directly on the T & G is basically a vapor barrier. I guess you could say it's a water shield too, but if water from outside were to penetrate that far into the roof package you'd have a very serious problem.Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Makes sense. Protects the T&G during construction, and is a lot easier to work on than poly.
They put up an new police station in the town near me, and it had an interesting roof. Rather than 1x or 2x's to create space for insulation, they had 16" high steel brackets that looked a bit like tripods. They placed them at about 2' o.c., screwed 2"x4" strapping to the top, and fastened the steel roofing to the strapping.
I haven't been been able to find out any thing more about them, and don't really feel like asking the cops.
Ok Thanks
Here are a few samples. Check out the tiny vent. I am building a house with exposed rafters,T&G and I deceided to just knock out the 2x4 lookout block and use a 4x16 vent over a piece of T&G. Not sure how I'm going to cut the hole out without weakening the board too much.Notice the 1x2 nailed to the bottom?
Timberpeg (when they don't use SIPS) uses a method called "wrap and strap".
T&G goes over the timber, using the mud sill, center girt, and top plate as nailing surfaces. Then EPS foam board (maybe 3 or 4") goes over the t&g. Then firring straps (1x3 SPF I guess). Then siding on the walls.
You are thinking about just about what I for my roof. 3x6 on 2ft centers with 1x knotty pine t&g decking. Originally mine was half inch Celotex on top of that and then a BU tar and gravel roof. No R value to speak of so I sprayed 2 inches of foam on the top and painted it. It has lasted 25 years but now is totally shot so now time for a redo. Not sure at this point which method I will use.