Hi All,
Question: Will 6″x5/8″ T&G pine ceiling boards span 39″ without sagging, if not will 3/4″ work. I can get the 5/8″ prefinished, but not 3/4″ prefinished. I really do not want to finish all those boards. There will be FG batt insulation above the ceiling.
This is for a 19’x16′ loft ceiling in a very old house. The ceiling boards will be nailed to 2×8’s sistered to existing roof rafters up to the existing rafter ties. 2×4 blocking will be installed between the 2×8’s every 24″. The blocking will allow every 4th board to be nailed midspan. Will it work?
I’m trying to keep this project as simple as possible. Adding intermediate rafters would make things very complicated.
Any thoughts would be appreciated
Replies
I'm assuming that this is a cathedral ceiling in the loft...
39" is a big span... even for 3/4. Any chance to block every joint? or even every other joint? Easier than adding a rafter (although there may be other reasons for adding a rafter... such as sag in the roof, bearing the load of the cieling... etc. Consult an engineer for that one)
For the record... I would add the rafters for roof stability and weight concerns from the cieling... but then again, I am a misogynist and an over-builder by nature! LOL
A few bucks to an engineer would answer the question... and may save a major failure... which would be my first concern.
Thanks for the feedback. Tt does look scary on paper. The house is soild brick walls. The original roof rafters are about 4"x6". They are actually trees saw on three sides, a couple still have bark on them. Mortise and tenon at the top, no ridge. Skip sheathing and a metal roof. It's hard to imagine they've stood their ground for 150 years. The real catch is they never had any collar ties. The 2nd floor ceiling joists run perpendicular to the rafters. I'll be adding collar ties above head height, but low enough to do some good.
Ill probably go ahead and add more blocking at 12" intervals. My engineer/architect wasn't concerned except for the lack of collar ties.
They don't build them like this anymore
browndog
Yea.. they certainly don't build 'em like that. Well... I have seen some pretty sturdy construction up in Amish country that might rival that... but even the Amish are downsizing their stuff.
I retract my concerns over the weight issue. You could probably hang a few Peterbilts from those "trees" and still have plenty of weight capacity! LOL
Changing your blocking schedule from 24" oc to 12" oc is going to make a tedious install. I would suggest increasing the distance between the blocking to maybe 72" oc and then add what would amount to an undersized rafter right down the middle of the original rafters between each block. This will decrease the span from 39" to 19.5". That should prevent sagging.
If you now think that the insulation you were going to place neatly between the 24" oc blocking will not fit in the new 19.5" spacing without a lot of speacial cutting, you can change the positioning of the new rafter so that you alternate bay sizes to roughly 16" oc and 24" oc. (39-16=23) Standard size batts will now fit and you'd still have no more than a 24" span for your ceiling boards.
Do you guys really think that 6"- 5/8ths pine is going to sag at 39inches?I mean it being t&g?
The final splash of SanchoRon receded from shore and returned to sea.Now but a passing memory to some, the fallen comrade to friends, and an unknown for those to come.The death merchants united dealt the blow to what aim?
Edited 3/4/2005 11:15 pm ET by the razzman
yep
That's a good idea, Ralph, alternating those little rafters. Could use insulation made for 19.2" spacing, too.
Hey. I was just today thinking about posting a "Hey Ralph Wickland" question...but now I've forgotton what for. CRS.Free the Sancho!
Excellent idea, thanks. I hadn't thought through the insulation all that well. Ill go with the 26"-13" pseudo-rafters.
Much appreciation
Browndog
you'll get a very "pleasent' scallop that you'll enjoy doing over again...
time and money... it's only a thing..
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WOW!!! What a Ride!
Please excuse my inexperienced intrusion but I'm trying to get a picture of what browndog is planning on doing here.
The ceiling boards will be nailed to 2x8's sistered to existing roof rafters up to the existing rafter ties.
The 2nd floor ceiling joists run perpendicular to the rafters. I'll be adding collar ties above head height, but low enough to do some good.
Is this a catherdal up to the peak or are the collar ties going to be forming a flat ceiling part way up?
Reason I ask is he said the roof is skip sheathing and a metal roof and he plans on using fiberglass batts above the ceiling.
Somehow that doesn't sound very good, kinda like a recipe for a soggy disaster if the batts are placed against the backside of any part of the roofing.
Seems someone should address the insulation concerns along with the t&g.
being just concerned
The final splash of SanchoRon receded from shore and returned to sea.
Now but a passing memory to some, the fallen comrade to friends, and an unknown for those to come.
The death merchants united dealt the blow to what aim?
Edited 3/5/2005 8:34 am ET by the razzman
I would have no hesitation whatsoever using the 3/4" on that span. I have never seen the 5/8"
It is only holding itself up with no other load.
I would NOT be adding the blocking between though. The T&G will act like strapping and do the same thing the blocking is doing structurally. I might add a face nail here and there though since one finish nail every 39" is not much. Or use glue to rafter on back sides.
But my real concern on this project is the insulation. Where can you get FG batts thirty something inches wide? Youwill have tremendous convection currents running in that space and probably condensation that then drips and stains the finished wood. If you can't get it blown with cells or BIBs at least place an inch of foam board between rafters along with the batts.
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The 5/8" T&G is from Michigan pre-stain. I haven't used it before, but getting it prefinished is a real plus. But, I'll be going with the 3/4"
Its not a straightforward sistering of 2x8"'s to the existing rafters. I'll post a pic of the design plan from work. I'm sure the design will raise a few comments.
In terms of the insulation, it won't be up against the roof deck. The 2x8's will run up to existing rafter ties, so there will be a flat portion of the ceiling in the middle. I'll be able to maintain a gap between the insulation and the roof deck and the area above the flat ceiling section is vented. the soffits aren't vented, but they leak air like sieves. I won't get as much ceiling insulation as would be ideal, but compared to what was there ( 3" on attic floor) it's a big improvement.
Thnaks for all the input
Browndog
You have soffits that leak like a seive.
You have attic space that is vented.
You are adding T&G that will leak like a seive.
You are using FG batts that leak like a seive.This new room will be ventilated like it has a window open - unless you use a VB between the T&G and the rafters. ignore that, and it won't matter how more heat you put in the house - as it gets sucked out the top, it will draw the moisture laden air with it to condense in the same space where you put the batts and you will have dampness and molds growing, possible water staining on your new work.
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There'll be a VB.
Here's a pdf of how the new ceiling rafters are installed. Feel free to comment. I'll pass em on to my arch./eng.
browndog
You decide for sure what you are going to do to insulate yet?
Ideally, I would blow in cellulose. But limited access once the ceiing is up put me off of that. That's why I opted for FG batts installed from below. A friend of mine suggsted putting up the angled portions of the ceiling, blowing in cellulose there and putting FG batts on the flat part of the ceiling, then finishing the ceiling installation. I'm going to look into the logistics of that idea, but seems like alotta work for a little gain.
Browndog
I looked at your drawing and would ask your engineer about using const adhesive and pneumatic nails instead of the screws. It would make for a quicker and stronger connection.