Hardie Board inside garage - we've flooded before

[jfoster]

Finally getting close to completion on the garage remodel/build. Last minute decision was to place 3x5 hardie board - the waterproof one - as the first course on the wall at the floor, and then transition to drywall above that. We've flooded twice in 20 years of living here but that was enough..and I'd like to avoid soaked drywall if it ever happens again - so I have a few questions.

https://www.lowes.com/pd/James-Hardie-0-42-in-x-36-in-x-60-in-Fiber-Cement-Backer-Board/1001066302

Am I correct in using normal tile thinset for the joints between the boards and also at the top where it will transition to drywall?

I'm thinking about putting tile on that first 3' - anyone done this? Where should the top tile land - at the very top edge of the hardie board? Any other ideas instead of tile?

One guy suggested to just stucco it and have a sanded finish at the bottom and transition to the drywall at the top w/knock down. I guess if the transition isn't perfect, I can put a piece of trim.

 

[PoorUB]

I park my truck right against the south wall of my garage. Over the years the sheet rock has gotten wet hundreds of times and eventually failed. I ripped off the sheetrock to 3 feet up and sheeted the wall with 3x5x1/2" sheets of concrete backer board. I used fiberglass tape on the lower part of the walls with thin set and at the top of the backer board to sheet rock I used fiberglass tape and drywall mud. Then I covered it all up to four feet with fiberglass reinforced panels. I used contact cement to glue on the panels and simply butted them together. I put a piece of PVC trim across the top edge and a 1x4 PVC board at the floor for base board.

I figure that wall will be there long after they bury me!

The one part of you plan that bothers me is you can cover the walls with concrete backer board, then the next time it floods how do you dry out the wall? The backer will seal up water inside and I would assume grow mold.

Personally, I would just sheetrock the walls up to four feet, no paint and the next time it floods tear it all off and throw it away, dry out the walls and re-sheet rock.

 

[nadogail]

The tiny room where my garage toilet is installed is paneled with FRP, it looks as nice as the day it was installed, about 20 years ago.

 

[flippin]

With the same concerns (water damage, wear & tear) I elected to use the same painted steel panels normally installed as exterior cladding. Installed with j-track top and bottom it was very easy and provided a perfect finished edge to transition to drywall etc. To add further durability I started with a course of pvc deck fascia board (1/2" x 9").

 

[egdede]

...I ripped off the sheetrock to 3 feet up and sheeted the wall with 3x5x1/2" sheets of concrete backer board. I used fiberglass tape on the lower part of the walls with thin set and at the top of the backer board to sheet rock I used fiberglass tape and drywall mud. ...

I watched a courthouse get 'drywalled' like this. No PVC, just a skim coat of hot mud over the cement board. It is stout as ****. I would do the bottom of my garage like this for sure.

 

[jfoster]

Thanks all. For the mold concern, there isn't much there to retain moisture and I will be running a dehumidifier. We have block walls, then insofast insulated Styrofoam panels (these are grooved on the backside where it meets the block wall and have integrated vertical ABS studs attached with construction adhesive. The hardie board would be attached directly to these insofast panels - so that's the only place where there would be a sandwich Hardie board in this case is that 100% waterproof version I linked above. We are also leaving 1" gap at the bottom.
Here is the insulated panel:

Shop UX 2.0 InSoFast Panels | InSoFast Insulation Solutions

The UX-2.0 InSoFast Panel provides R-8.5 continuous insulation for interior or exterior use. Built-in studs, drainage channels & electrical raceways.

www.insofast.com

 

[K'ledgeBldr]

Personally, I would just sheetrock the walls up to four feet, no paint and the next time it floods tear it all off and throw it away, dry out the walls and re-sheet rock.

This^^^
Drywall is cheap- plus you definitely need to dry out the wall cavity- whatever you use- so the cheaper the better!

 

[duneslider]

The one inch gap will be enough to let moisture out. You could cover the gap with a trim and if there is a flood just remove the trim to facilitate drying.

No reason to do any seams with thinset UNLESS you are going to tile it. If you are going to tile it then yes use alkaline resistant mesh tape and thinset. If you are just going to paint it then just finish it like drywall. If you skim the whole board with drywall mud and sand it will look like drywall when painted. Another option is to just use the GP Densshield. It will do what you need here too and might be easier to finish. It is gypsum based but doesn't break down in water. I have had pieces on the side of my house for years through rain, snow and it has not broken down.

 

[ace10]

I used LP Smartside for my garage's wainscoting.

There are other, durable, water-resistant sheet goods as well. I don't think a cementitious board would be among my top choice.

 

[wrenchguy]

I'd screw it on for removal when drying out. Make it easy, so what if ain't finished to hilt.

 

[K'ledgeBldr]

The one inch gap will be enough to let moisture out. You could cover the gap with a trim and if there is a flood just remove the trim to facilitate drying.

The 1" gap will let "water" out- but a 1" gap at the bottom of a stud cavity won't DRY OUT the cavity- unless there's a equal or greater size gap at the top of the wall- think convection.

 

[Hank11]

If it floods again (enough to get in the walls) you will want to immediately remove the bottom 2-4 feet or so of the wall covering and insulation if any for it to dry properly. I think you may be working yourself into a trap.

 

[jpaw]

The cheapest way.
Depending on how high the flood line is I would encapsulate the first 2 or 4ft so that it can't wick further up the wall and insulation. Put a painted board between the sheetrock at the 2 or 4ft line so the lower half can quickly be torn out and replaced. Also do the same with the insulation.

 

[jfoster]

This^^^
Drywall is cheap- plus you definitely need to dry out the wall cavity- whatever you use- so the cheaper the better!

The board is up against the Styrofoam insulated board so there isn't technically a "cavity" - but I can see the potential for a moisture sandwich.

The one inch gap will be enough to let moisture out. You could cover the gap with a trim and if there is a flood just remove the trim to facilitate drying.

No reason to do any seams with thinset UNLESS you are going to tile it. If you are going to tile it then yes use alkaline resistant mesh tape and thinset. If you are just going to paint it then just finish it like drywall. If you skim the whole board with drywall mud and sand it will look like drywall when painted. Another option is to just use the GP Densshield. It will do what you need here too and might be easier to finish. It is gypsum based but doesn't break down in water. I have had pieces on the side of my house for years through rain, snow and it has not broken down.

The reason I was considering tile was because if you use drywall mud and knockdown, that part will still be damaged by water.

 

[duneslider]

How much flooding are we talking here. Like you get 3 feet of water, or maybe a few inches up the wall?

 

[jfoster]

How much flooding are we talking here. Like you get 3 feet of water, or maybe a few inches up the wall?

twice in 20 years we had water in the garage. The last one was a couple years back and it was 20 inches.

 

[Daniel Dudley]

Would you consider using metal agricultural roofing? It goes up fast, and it can make great wainscotting. It also comes prefinished, and doesn't need skim coating.

 

[jfoster]

At this time, the hardie board is installed. They taped the top seam - so now I just need to decide if I want to tile this disaster or perhaps have the stucco guy who is coming to do the outside take a look at stucco for the bottom of the wall (3' up) and use a type of chari molding to split the sanded finish on the bottom and the knockdown above it.

 

[Gman1954]

I have a 21x26 Timber Frame Garage/Art Studio & thought about Hardie Board over top of Rock Wool for Fire Resistance.. Need something that won't get wet & moldy in this humid weather (45 inch /year). Metal Roofing is a Good idea too.
My brother recently told me about TRUSSCORE PVC panels : looks really tough, like FRP or PVC sheets, but precut and easier to put up plus they have Pre-Molded Slat Wall Panels too. Anyone Used it yet?