Ceiling drywall, can I hang it from my rafter ties?

[ChuckGm3]

Check out my crude illustration below and let me know what you think.

I already have OSB "floor" in about a 16'x8' section sitting on top of these rafter ties for about 400 lbs worth of storage space (with a pull down ladder). R13 has been stapled up under the floor and R26 everywhere else)

Ought I be concerned about the weight of another 6-700 lbs of drywall on these 16' spans?

 

[Styx]

Correct me if I'm wrong but the rafters just hold the joists together and the weight goes to the foundation on the outer walls... I don't see a problem with dry walling the rafters... I wouldn't be using it for storage tho unless its engineered for it...


Cheers...

 

[Falcon67]

Yes you should because the farther up the rafter your tie goes, the greater strain it puts on the rafter and the greater pressure on the walls. One calculator I used shows that on a 4/12 pitch with 48" from plate to ridge, raising the rafter tie from plate level up 24" doubles the wall pressure. Since raising the tie increases the loads, during any design the rafter size would be increased to compensate.

After that, drywall is going to sag at 24" OC IMHO.

 

[ChuckGm3]

Yes you should because the farther up the rafter your tie goes, the greater strain it puts on the rafter and the greater pressure on the walls. One calculator I used shows that on a 4/12 pitch with 48" from plate to ridge, raising the rafter tie from plate level up 24" doubles the wall pressure. Since raising the tie increases the loads, during any design the rafter size would be increased to compensate.

After that, drywall is going to sag at 24" OC IMHO.

One measurement I didn't add to the diagram is my ridge to tie. It's about 48" and in actuality I'm not sure it sounds as a true rafter tie. It rests on top of the right hand wall like a ceiling joist, but ties to the rafters on the left hand wall, so a bit of a hybrid model.

 

[bczygan]

Use 1x2 strapping perpendicular to those members at 16"o.c. and use lightweight drywall. Make sure the connection of the rafter tie/ceiling joist to the rafter is adequate.

Alternate solution: Metal (Steel or aluminum) or plastic ceiling panels.

What's the span of the 2x4 rafter tie, from the wall on the right, to the rafter on the left?

Bill

 

[ishiboo]

Another idea:

https://www.menards.com/main/store/..._Spec/2015B_I-Span_System_Brochure_lowres.pdf

 

[ChuckGm3]

Use 1x2 strapping perpendicular to those members at 16"o.c. and use lightweight drywall. Make sure the connection of the rafter tie/ceiling joist to the rafter is adequate.

Alternate solution: Metal (Steel or aluminum) or plastic ceiling panels.

What's the span of the 2x4 rafter tie, from the wall on the right, to the rafter on the left?

Bill

I have also considered vinyl soffit, ceiling tiles etc. but those are more expensive than drywall.

The 2x4's are 16' long from wall to ceiling rafter. The whole garage is 20.5' wide so about 5' of that left side would have the ceiling mount directly to the ceiling rafters.

 

[bczygan]

My only worry is that the 2x4 spanning that distance and the connection to the rafter.

It's not so much failure I'm worried about, it's the deflection. Too much and you will get cracking of the drywall joints.

You have snow?

What type of shingles and how many layers?

One layer of 3 tab, OSB or ply deck (Not board) and no snow and I'd do it. But to maximize the load capability of the 2x4's I would glue and screw some 3/8" plywood (Not OSB) on one side of each one, forming a gusset with the rafter and other framing, and shortening it's span and increasing it's effective depth.

Bill

 

[kv501]

Use 1x2 strapping perpendicular to those members at 16"o.c. and use lightweight drywall. Make sure the connection of the rafter tie/ceiling joist to the rafter is adequate.

Alternate solution: Metal (Steel or aluminum) or plastic ceiling panels.

What's the span of the 2x4 rafter tie, from the wall on the right, to the rafter on the left?

Bill

No way. His concern is weight and the stringers you mentioned on 16" centers would add right around 17.5 lbs without screws (per 4x8 sheet). The difference between a sheet of 1/2" vs 5/8" drywall is 19.2 lbs. That would be an ridiculous amount of extra work for almost no benefit. Put 5/8" up and call it good. It's about a dollar per sheet more, so for your job it would be roughly $10. You won't get 200 feet of 1x2 and extra screws for that, let alone the time cutting and placing them.

 

[ChuckGm3]

My only worry is that the 2x4 spanning that distance and the connection to the rafter.

You have snow?

What type of shingles and how many layers?

One layer of 3 tab, OSB or ply deck (Not board) and no snow and I'd do it. But to maximize the load capability of the 2x4's I would glue and screw some 3/8" plywood (Not OSB) on one side of each one, forming a gusset with the rafter and other framing, and shortening it's span and increasing it's effective depth.

Bill

No snow. I'm in the valley in Southern CA. The roof is OSB with asphalt shingles. It's also probably worth noting that I have a solar PV system with 18 panels on the left slope of the garage.

So when you say add a plywood gusset to each, you mean at the vertical framing (that attaches to the ridge) like this?

 

[kv501]

My only worry is that the 2x4 spanning that distance and the connection to the rafter.

It's not so much failure I'm worried about, it's the deflection. Too much and you will get cracking of the drywall joints.

You have snow?

What type of shingles and how many layers?

One layer of 3 tab, OSB or ply deck (Not board) and no snow and I'd do it. But to maximize the load capability of the 2x4's I would glue and screw some 3/8" plywood (Not OSB) on one side of each one, forming a gusset with the rafter and other framing, and shortening it's span and increasing it's effective depth.

Bill

You're adding time, weight, and complexity to a problem that using 5/8" sheetrock would solve on it's own. I have a 16' 6" x 24' section of my garage with 2x4 rafter ties/ceiling joists going the 16' direction. Hung 5/8 in 2008 below a 4/12 roof and there is zero sag or cracking.

I live in NW Iowa where temps range from -30 to 105 F and it's one of the windiest places in the country.

 

[bczygan]

If going 5/8 I would for sure use the lightweight stuff.

And gussets where you showed as well as at the rafter to rafter tie/joist. Bigger gussets equal better. Both sides equals better.

How much do the PV panels weigh?

Bill

 

[ChuckGm3]

You're adding time, weight, and complexity to a problem that using 5/8" sheetrock would solve on it's own. I have a 16' 6" x 24' section of my garage with 2x4 rafter ties/ceiling joists going the 16' direction. Hung 5/8 in 2008 below a 4/12 roof and there is zero sag or cracking.

I live in NW Iowa where temps range from -30 to 105 F and it's one of the windiest places in the country.

Any additional weight on top of those 2x4's like I have though? Insulation and/or storage?

 

[ChuckGm3]

If going 5/8 I would for sure use the lightweight stuff.

And gussets where you showed as well as at the rafter to rafter tie/joist. Bigger gussets equal better. Both sides equals better.

How much do the PV panels weigh?

Bill

http://www.homedepot.com/p/SHEETROC...pered-Edge-Gypsum-Board-14113812408/203021463

This is the stuff I was considering. 51.2 lbs per sheet.

The PV panels are 35lbs each. About 720 for the entire array including mounting hardware.

 

[kv501]

Any additional weight on top of those 2x4's like I have though? Insulation and/or storage?

5/8" plywood deck, architectural shingles (they weigh about 80% more than three tabs which no one uses anymore), r15 batts, and about 6 Rubbermaid totes full of paper documents. And a LOT of snow.

 

[kv501]

http://www.homedepot.com/p/SHEETROC...pered-Edge-Gypsum-Board-14113812408/203021463

This is the stuff I was considering. 51.2 lbs per sheet.

The PV panels are 35lbs each. About 720 for the entire array including mounting hardware.

I have never hung the lightweight shee trock so I should throw that out there. I hung std weight material under the conditions above and if it had sagged the ceiling (as in the entire thing, not just joist to joist), it would have shown cracks, which it has not. As to whether you will get sagging with the lightweight material someone else may be able to comment. It's only been out for a few years but I haven't heard of any problems.

 

[kv501]

If going 5/8 I would for sure use the lightweight stuff.

And gussets where you showed as well as at the rafter to rafter tie/joist. Bigger gussets equal better. Both sides equals better.

How much do the PV panels weigh?

Bill

Why?

I have an almost identical situation to the OP, with 5/8. It's been there through 7 winters, 4 of them unheated and hasn't moved at all. Why tell the OP to go through tons of extra work and expense just going by gut feel?

 

[bczygan]

Why?

I have an almost identical situation to the OP, with 5/8. It's been there through 7 winters, 4 of them unheated and hasn't moved at all. Why tell the OP to go through tons of extra work and expense just going by gut feel?

Are your ceiling joists 2x4's? Do they span as much as the OP's? What species of wood are they and the rafters?

And now the OP adds PV panels. And does he want to store heavier things? And heavier materials?

You're right.

Maybe it's time for some calculations and engineering, rather than using your example or my guessing.


Bill

 

[kv501]

Are your ceiling joists 2x4's? Do they span as much as the OP's? What species of wood are they and the rafters?

And now the OP adds PV panels. And does he want to store heavier things? And heavier materials?

You're right.

Maybe it's time for some calculations and engineering, rather than using your example or my guessing.


Bill

Read posts #11 & 15 Bill.

It's quite literally the same as what the OP has described, only tried and true with 7 winters of heavy snow load. The reason I gave my example is because it's evidential and isn't based on guessing or subject to over engineering and screwing extra boards all over the place.

 

[James-W]

I always thought 5/8 was code for a ceiling. I think I read that somewhere, or someone told me, I don't recall which. Is that wrong?

 

[kv501]

I always thought 5/8 was code for a ceiling. I think I read that somewhere, or someone told me, I don't recall which. Is that wrong?

The IRC addresses ceiling thickness and states that 3/8 should not be used on ceilings which support insulation or where a water-based texture is used (1/2 and 5/8 is okay).

Where water-based texture is used, the sheet rock has to be run perpendicular to the joists; 1/2" can be no more than 16" OC, 5/8" no more than 24" OC.

However, you'd have to check in your municipality what codes, if any, apply.

Where I live there are no residential construction inspections unless it's required by your insurance. A friend and I built a 18x52 garage (long skinny lot) for some older friends of ours 2 summers ago and a $35 building permit was all we needed. No one, and I mean no one, from the city or county so much as stopped by to look at it. I thought they'd at least check the height or square footage, but nope.

An "inspector" from the owners' insurance company stopped right after we finished framing it but he was there for maybe 20 minutes. Walked around with a clipboard but that was it. No tape measure, no pictures, etc. Before he left he came up to us, asked if we were doing the roof (yes), and said he needed to make sure we use 7 nails per shingle. We said ok and he got in his car and took off. We live in thunderstorm and tornado alley, and I'm pretty sure roof claims are insurance companies' biggest headache around here.

From the time I've spent in California I'm pretty sure you have to get Vladimir Lenin himself to sign off if you want to change the color of your curtains, so you might want to check into it.

 

[Gerald O]

You can strap the ceiling with 1x3s at 16"OC and then use 1/2" lightweight drywall. No sagging and less weight overall than just 5/8".

 

[maxpower_hd]

I always thought 5/8 was code for a ceiling. I think I read that somewhere, or someone told me, I don't recall which. Is that wrong?

It may depend on where you live. I was required to use 5/8 and it was inspected before I was allowed to continue. But it is only required on ceilings and walls where there is a living space on the opposite side. Otherwise I could have used 1/2" and did on the second floor and walls not adjacent to living spaces to save money.

 

[ChuckGm3]

5/8 is fire code, but while this is an attached garage, the house-side wall is a sealed off fire-barrier already so I'm not required to have a fire-code ceiling I don't believe.

Having worked with 1/2" and 5/8" in the past, that extra 8th makes a huge difference in the weildability. I could install 1/2 by myself, 5/8 will require at least one extra set of hands and a hoist. So from an installation standpoint, the 1/2 would be great.

I suppose going 5/8 would give the added re-sale value since it could technically be turned into a living space at that point.

The other option I'm considering is CeilingLink (Like Ceiling Max but I think a better product) direct mount tile grid plus some Armstrong A-fire code rated lightweight tiles... this would wind up being about 3x the $ of drywall, but also about 1/3 the effort. Also makes things like adding additional lighting/outlets, etc. much easier down the road.

I'm putting off finishing the ceiling right now until I install my Liftmaster Jackshaft 8500. I figure why custom fit the ceiling around my opener (only to patch those holes later) when I can just get rid of it now.

 

[Gerald O]

5/8 needs to be type X for fire separation where code requires. That would generally be only on garage ceilings where there is a living space above, not for adjacent living space.

5/8 type X weighs about twice as much as the typical light-weight 1/2".

 

[jim whitney]

5/8 is fire code for a ceiling with living quarters above or an attached garage on the wall abutting the house. Sometimes they will require double layer of 5/8 for above living quarters.

 

[ChuckGm3]

So lightweight 5/8 vs 1/2... only real benefit is the 5/8 shouldn't sag but the 1/2 might?

 

[ChuckGm3]

Went with the 1/2" sheet rock.