# Exposed Timber Floor Joists + Drywall Ceiling



## jb9 (Jan 13, 2017)

Hello,

I am curious as to how a pro would approach doing drywall in between exposed timber joists on a ceiling. The timbers are going to shrink about a 1/16" on each side over time most likely. Here are what I perceive to be my options:

-Drywall sheets laid down on 2nd floor above. Can the drywall handle the compressive pounding as a bearing surface against the floor joist? It would obviously resolve the timber shrinkage issue.

-Lay down sleepers on the timber joists. Lay down subfloor above. Use the gap created by the sleepers to slip in a cut piece of sheetrock. Gap would be large enough to exceed expected shrinkage.

-Lay down subfloor above. Cut drywall to fit. Expect to go back in a 4 years or so and patch any gaps with joint compound.


I would be curious to hear how a drywall pro might approach this job and if there are other solutions I haven't thought of.

Thanks in advance. I've learned a lot from the pro's here... Drywall is not my trade.


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## Philament (Dec 9, 2014)

Are we talking timber frame (post & beams style) timbers or just regular 2x joists? What sort of joist spacing?


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## jb9 (Jan 13, 2017)

Good question. Timber Frame style. Exposed Douglas Fir with 24" OC spacing in between joists.


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## Philament (Dec 9, 2014)

jb9 said:


> Good question. Timber Frame style. Exposed Douglas Fir with 24" OC spacing in between joists.


What sort of subfloor are you using to span 24" OC?

You might want to red up on some of Ted Benson's books and his Open-Built systems, they will show you some solutions.


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## jb9 (Jan 13, 2017)

Probably Advantech 23/32" subfloor. Their span tables indicate this thickness will work with 24" spans.


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## hdavis (Feb 14, 2012)

I'd ask Blacktop what he'd do. J beads can cover some movement and give a clean edge.


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## Anti-wingnut (Mar 12, 2009)

I'd do something like this


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## Defenestrate (Aug 13, 2015)

Maybe this? http://www.trim-tex.com/products/overview/commercial-beads/tear-away-beads/super-seal-tear-away-l-bead/


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## jb9 (Jan 13, 2017)

This is helpful. By running the strapping along the beam like you sketched out, would that keep the gap sealed as the floor joist experienced its shrinkage? I was looking at the trim-tex catalog to figure out their range of products and what each bead is used for.


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## rustyjames (Aug 28, 2008)

I would go with antiwingnut's approach, but probably a little less on the reveal.


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## Anti-wingnut (Mar 12, 2009)

jb9 said:


> This is helpful. By running the strapping along the beam like you sketched out, would that keep the gap sealed as the floor joist experienced its shrinkage? I was looking at the trim-tex catalog to figure out their range of products and what each bead is used for.


As per my detail, if it moves around a little, it won't matter all that much because you'll be looking up into a reveal painted (at least as far as I would do it) flat black.


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## jlhaslip (Dec 31, 2009)

Going back to the question asked above and not yet answered:

What size are the joists?

On larger joists, using a strip of plywood about an eighth thicker than the drywall down the middle of the joist allows the board to be installed afterwards. Make sure there is enough space to allow the board to move enough to get the piece into one side and then slide it into the other joist gap.

On narrower joists, the above approach is not an option, so go with the pull strip plactic fillable mouldings. 

Tape off the joists prior to mudding because, well, you know, mudders can get sloppy.


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## jlhaslip (Dec 31, 2009)

Something like this.

And make sure the subfloor is 2 x 4 on edge or larger so you will have a place to run electrical and plumbing.


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## Philament (Dec 9, 2014)

jlhaslip said:


> Something like this.
> 
> And make sure the subfloor is 2 x 4 on edge or larger so you will have a place to run electrical and plumbing.


This is the route I was going to suggest, using 2x4 "purlins" perpendicular to the joists on sleepers, then just put the drywall in like a T-bar ceiling, butt board if any splices are needed. I don't really like the idea of fastening it to the underside of the advantec. There's a lot of details missing to really say what the best route is. Is this a new build, renovations, just on the drawing board, any mechanical required...?

If you have the head room above, going to the adjustable subfloor above the the joists (a la Ted Benson method) is ideal.


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## archtimb (Mar 25, 2007)

jlhaslip said:


> Something like this.
> 
> And make sure the subfloor is 2 x 4 on edge or larger so you will have a place to run electrical and plumbing.


This is close. Smaller bearing strip, increase the drywall lip, and fasten the drywall directly to the joist. If the the drywall color is known, paint, or at least prime before installation. Stops the inevitable paint line when the joist shrinks. 1/2 or 5/8 drywall will easily span without any field fasteners. 

This yields the cleanest edge in my experience, in 30 years of Timber Framing. Yes, Benson's methods are exemplary, but my Clients could not afford them.


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## jb9 (Jan 13, 2017)

This is very helpful. Thanks Jihaslip and Archtimb. I am leaning towards this solution with a sleeper on top of the floor joist. Joist dimension is going to be 3" x 8" (true size, not dimensional lumber) with a height reduction towards the mortise pocket they will fall in. That is the aesthetic I am going for. I like how white or a light color of drywall makes the room brighter and the timbers "pop" in the light.

If I were to fasten the drywall to the joist, wouldn't it pull laterally and eventually crack?

Also, I am going to be running SIPS with all electrical chases in the exterior walls, plumbing is completely isolated in a single service cavity at another location in the house (zero depth floors with thicker Advantech and a sound barrier, I know this isn't great but I'm OK with it). Interior walls will have electrical. Ductless Mini Split for heat (plus a wood stove maybe).

Tight envelope. I actually did glean a bunch from Ted B.'s Unity Homes approach. I guess I'm trying to emulate some of his design concepts but I am just trying to figure out how to best execute this detail of the drywall ceiling/Timber Frame exposed joist. I can post a picture of the model if folks are interested.

Thanks. Lots of good ideas and friendly suggestions here.

I appreciate it.


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## archtimb (Mar 25, 2007)

Geographic location (IE: humidity and temperature range) and what species?

I never saw any tear-out from this method, and I worked in unseasoned Oak in the mid-atlantic/new england area. Some Clients preferred the drywall ceilings, but most enjoyed the drywall walls playing against the wood ceilings. The biggest complaint about drywall ceilings I ever heard was "it's so much edging/cutting in" with finishes.


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## jb9 (Jan 13, 2017)

Thanks Archtimb.

Species will be Doug Fir. Site is in Idaho. One more question. Does this method require installation from above (2nd floor) before one puts down the Advantech sheets? I always thought this method involved slipping the drywall sheet in by using the gap on either side. 

And does the bead (J-bead etc) give the drywall strength from a compressive strength standpoint? I always wondered if the drywall would crush by being in the zone near the subfloor.


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## Anti-wingnut (Mar 12, 2009)

J-bead had no strength as far as this conversation is involved


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## jlhaslip (Dec 31, 2009)

I have seen 8 x 8 Douglas Fir timbers twist enough to damage those zip strips and that is why I suggest the method I drew up. I would not fasten the drywall to the timbers, either. If you must fasten them, do it in the centre of the face of the drywall and let the edges fall onto the joists over time.
Agreed that priming and painting prior to install is the way to go, with the nail holes patched afterwards if they get screwed off in the centre as I have described.


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## archtimb (Mar 25, 2007)

D. Fir 3x6, by the time we got DF on the east coast, it tends to be fairly stable shrinkage wise.
You may get fresher material there, so be careful. There is NO need to even fasten the GPDW. It can totally float if you desire. Our fastening was minimal, more to keep it aligned than "hanging" as in conventional. 

Yes. Apply the GPDW from the top. Any effort to install afterwards makes a mess. You will either roll back a GPDW paper face, or get gypsum all over your nice timbers.

J mold is not used with this technique, but yes it can stiffen the GPDW edge. It was recommended to me and I used it in 1981. Never used it again...

The thicker "sleeper" atop the joist stops any compression damage.

In the sketch from Jlhaslip, you can leave a reveal at the timber. Makes a nice shadow line, and it is easier to cut in finishes. But, in my experience I have seen much more infiltration of dust years later with this look. 

Don't forget to cut tapered edges off the GPDW. Looks like hell later. And 14-16" sheets eliminate butt joints, in most Timber Frame designs.

Whew! Did I miss anything? ;o)
Next step would be a 4-5 year apprenticeship. I'm too old for that!


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## jb9 (Jan 13, 2017)

Thanks Archtimb and Jlhaslip. I think this idea is the best way to achieve my goal. Thanks for clarifying that it needs to be done from the top first too. I'm going to try and ensure that the Doug Fir timbers are as dry as I can get them from a stability standpoint too. Doing the Advantech and the ceiling sheets of drywall in the same process might be a little trickier but I agree that the result will be better. I actually like the floating ceiling if it can work. It's the execution details that really matter so I sincerely thank you for these thoughts.


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