Moisture Break For Drywall

[danho]

I am working on insulation and air sealing my shop today and planning ahead on sheetrock in the coming days. I have a 2' tall exterior block stem wall, above grade, and as of now am looking at green board with 1/4" gap above the stem wall for the bottom course with traditional sheetrock elsewhere. I do not plan on getting the walls wet, but in case I want to hose the shop out or similar down the road, are there any recommendations for my install out of what I already mentioned, knowing that the greenboard is for mold only? Not looking for plywood instead of drywall recommendations but obviously open to your thoughts on a moisture break. This is an ounce of prevention is worth a pound of cure question for me and I am trying to maintain a "budget"......

Thanks in advance.

 

[PCustoms]

How high up the wall would you be hosing?

Drywall, green or not, isn't meant to be hosed down. If your worried about moisture on top of the wall, I'd leave more gap and hide it under PVC trim. You can caulk the trim to the top of the wall.

 

[billconner]

I don't know your plan for ledge created by stem walk but you might think about a piece of pressured treated lumber or PVC trim - a 1x3 or 1x4 - and letting drywall sit on it. I might set it in a J-bead for a clean joint. Or shim it 3/8" on stem wall and stuff 1/2" backer rod to air seal and protect edge of drywall from block moisture.

I'm not convinced the green board gets you much over plain. Cost may kill this - I don't know - but paperless drywall is superior for moisture resistance to green board. You might look at it.

 

[Rusted Nut]

Drywall and water are not a good mix, no matter what type. You can get blue or purple drywall, which is water resistant, green is moisture resistant. Regular drywall with a good coat of exterior paint, hung with a 1/2” gap that is caulked , would be the best value. Unless your garage is very moist, green board is not going to do you much good. You could glue on a 4’ piece of FRP over regular drywall, that would provide some water deflection properties.

What are doing that requires hosing out the shop, that couldn’t be cleaned by sweeping of blowing out with air?

 

[Fav Onefour]

I have a similar wall setup in a garage. My walls would get wet from snow dropping off vehicles, washing, and condensation. I don't know many materials that would take the moisture from the front and back side.


I ended up using foundation panels with grit surface to the inside. I painted the grit side and glued the panels to the stem wall. I sealed the panels along the floor and top edge seam. My walls had been sheetrocked years before right down to the stem walls. The bottom of the rock was already showing abuse from moisture. (Mainly condensation) I really like the idea of using trim at the bottom of sheetrock. If I had a chance to do it again, I'd do PVC from the sill to the outer edge of the foam board and start rock above.

Biggest disadvantage is the lack of durability. The foam is not a material that will take a lot of banging and bashing.

 

[nadogail]

I have found that FRP ( fiber reinforced plastic) panels are almost perfect for wet areas.
FRP is used in commercial kitchens that get hosed down. If it’s tough enough for the restrooms at McDonalds; it will be good for any garage.
I used a notched spreader and the special adhesive sold at Lowes and Home Depot. I glued the FRP directly to the Drywall, they sold me trim strips for the panel joints and corner trim.
You can have any color you want, as long as it is White.

 

[danho]

How high up the wall would you be hosing?

Drywall, green or not, isn't meant to be hosed down. If your worried about moisture on top of the wall, I'd leave more gap and hide it under PVC trim. You can caulk the trim to the top of the wall.

I won't be hosing the wall, it would be potential splash from the floor or moisture creep.

 

[danho]

I don't know your plan for ledge created by stem walk but you might think about a piece of pressured treated lumber or PVC trim - a 1x3 or 1x4 - and letting drywall sit on it. I might set it in a J-bead for a clean joint. Or shim it 3/8" on stem wall and stuff 1/2" backer rod to air seal and protect edge of drywall from block moisture.

I'm not convinced the green board gets you much over plain. Cost may kill this - I don't know - but paperless drywall is superior for moisture resistance to green board. You might look at it.

No plan for the ledge, but thanks for the ideas and I'll look at the paperless drywall.

 

[danho]

Drywall and water are not a good mix, no matter what type. You can get blue or purple drywall, which is water resistant, green is moisture resistant. Regular drywall with a good coat of exterior paint, hung with a 1/2” gap that is caulked , would be the best value. Unless your garage is very moist, green board is not going to do you much good. You could glue on a 4’ piece of FRP over regular drywall, that would provide some water deflection properties.

What are doing that requires hosing out the shop, that couldn’t be cleaned by sweeping of blowing out with air?

Nothing requires hosing out, I just asked an in case question.

 

[Firstram]

You could run 1 course of 1/2” cement tile backer around the bottom.

 

[billconner]

For moisture/water concerns, I'd use a setting type mud instead of drying (powder vs. ready-mix) along with a fiberglass tape. I believe it resists moisture better. The paperless drywall can be used in place of cement board.

 

[larry4406]

I think I would do the pvc base trim tight to the top of the block. OSI Quad caulk the pvc to the block and just be careful when washing and not be a wild man with the hose.