Drywall directly on interior concrete wall?

[exalted512]

Long-story-short, we had to switch builders and so some things are having to be worked through in the middle of our new construction build.

We have a poured concrete storm room that is not connected to any exterior walls. It also doesn't have any HVAC, just a dehumidifier. To help in the event of a fire, it was recommended to have double-stacked fire-rated drywall on the exterior of this room. But the previous builder (who was also the architect) didn't leave room for even 3/4" furring strips. I know with concrete, there's a moisture issue. But this room is completely interior. So would it be okay to durabond drywall directly to the room? Or is it something that I might just have to live without (the extra drywall).

If it is something I can do, is there a recommended time to wait to attach the drywall after pouring it? It's only about 10 days old at this point.

Thanks!

 

[The Cobbler]

drywall on concrete inside is done all the time. slap dobs of premix on the wall, drive concrete nails into the drywall/concrete
I question how much you need this tho, with the concrete itself it should be a fairly good rating. do you have specs on it as is?

 

[rlitman]

If you're worried about moisture, use the yellow paperless exterior rated drywall.

https://www.lowes.com/pd/DensGlass-Common-5-8-in-x-4-ft-x-8-ft-Actual-0-62-in-x-3-99-ft-x-7-99-ft-Drywall-Panel/999946288

 

[exalted512]

drywall on concrete inside is done all the time. slap dobs of premix on the wall, drive concrete nails into the drywall/concrete
I question how much you need this tho, with the concrete itself it should be a fairly good rating. do you have specs on it as is?

Thanks for the info! I couldn't find a lot of info about interior walls online, mostly just basement walls. I understand that concrete inherently has moisture, so I wanted to confirm.

It has 8" walls and a 10" ceiling. We live in a secluded area and have had widespread fires in the past. I'm concerned about a "what if the house burns completely down and no one ever puts it out" scenario. At this point, I'm not worried about the room collapsing, but I do want to prevent the inside from getting hot enough to damage what is inside. After talking with a lot of different people, the setup with this amount of concrete, plus doubled up fire x drywall with offset seams, and insulating the inside should be enough to keep the interior at a reasonable temperature. As a note, the intent isn't to keep people safe from a fire.

 

[kelpaso1]

.....

 

[Sumboodie]

This panic room is outside? Or it's in the basement of the not built house?

 

[larry4406]

Floor drain for dehumidifier?

Why do you need drywall? Fire rating or just make it pretty? If the later can you skin it with Hardie panel?

 

[mike93lx]

What are you using for a door that will be fireproof?

 

[mike93lx]

This panic room is outside? Or it's in the basement of the not built house?

Looks like a house is being built around it

 

[yeldogt]

Why would you need drywall on a concrete bunker ?

Why would you ever entertain staying in there if there was a fire ?

 

[65ranchero]

Why would you ever entertain staying in there if there was a fire ?

As a note, the intent isn't to keep people safe from a fire.

This is what he said

I think the OP intent is to have a fire resistant room for documents and possibly heirlooms!

 

[rjn2649]

Not an expert, but the R value of drywall is less than 1. I don't see it insulating well against heat, could be way off base. I would think steel studs, insulation. Fiberglass w/o paper? Then drywall on the inside would be best to keep contents safe. And maybe a Halotron sort of extinguishing system IF things really get out of control.

 

[wssix99]

I think the OP intent is to have a fire resistant room for documents and possibly heirlooms!

A quality fire safe will cost thousands less and do a much better job.

I would just plaster directly over the surface. Skip the drywall entirely - it's useless here.

 

[NUTTSGT]

If you are expecting drywall to prevent damage to items inside that room with concrete walls, you have more important things to worry about.

I'm guessing those walls are 8" thick ?

 

[ConCretin]

Once the concrete cures, there won't be ongoing moisture issues so that's not a concern. I'm not an expert on fire protection but I question the viability of adding it to the design brief. Providing physical shelter for a short period during a weather event is pretty simple compared to protection against fire. Drywall questions aside, i think the door is the weak point. With that said, I think I'd do as wssix99 suggests and plaster over the concrete and stick a fire safe inside.

 

[FMB4]

Your thread title talks of applying drywall on the interior of concrete walls. Yet your text talks of doing the same on the the exterior of said concrete walls.

Quote " To help in the event of a fire, it was recommended to have double-stacked fire-rated drywall on the exterior of this room."

Sorry, but I'm not understanding what you're trying accomplish.

 

[rlitman]

Not an expert, but the R value of drywall is less than 1. I don't see it insulating well against heat, could be way off base. I would think steel studs, insulation. Fiberglass w/o paper? Then drywall on the inside would be best to keep contents safe. And maybe a Halotron sort of extinguishing system IF things really get out of control.

Sheetrock is often used to line Class 350 fire safes. The plaster it contains will breakdown when exposed to fire, releasing water vapor in the process. It's an endothermic process like a phase transition that buys you a significant amount of time. Much more than the R value alone would imply, which is why sheetrock is used in preventing the spread of fire. However, the breakdown of the plaster will lead to its collapse, which is why fire rated sheetrock has embedded glass fibers.

The steam released by the plaster will displace air in the safe, which also helps prevent flashover inside. It does however not much else good for the contents.

 

[rjn2649]

@ rlitman Thank you the the info, then my thought (even for the wrong reason) would be better than drywall on the OUTSIDE of the shelter/safe.
EDIT: I just looked at the pic again. I meant the steel studs insulation and drywall on the INSIDE. I see wood studs inside, I THINK replace that w/ steel. ON the exterior, for smooth painting surface I would go with plaster directly troweled over the concrete, it might be hard to find a good plaster guy (or gal) then drywall glued up would e 2nd choice.

 

[FMB4]

@ rlitman: ya, I knew all about that. Well, not really, but thanks for posting that important info.

 

[yeldogt]

This is what he said

I think the OP intent is to have a fire resistant room for documents and possibly heirlooms!

missed that on the second post of the OP

 

[yeldogt]

FYI: Unless there is some flammable liquid -- house fires in a basement don't get that hot ... unless part of a mass fire. I have had two major fires and water does more damage .... don't know what the OP wants to save. Even my rural one that took quite a while to put out -- the stuff the basement was just wet

 

[mike93lx]

FYI: Unless there is some flammable liquid -- house fires in a basement don't get that hot ... unless part of a mass fire. I have had two major fires and water does more damage .... don't know what the OP wants to save. Even my rural one that took quite a while to put out -- the stuff the basement was just wet

Sure doesn't look like a basement to me.

 

[PCustoms]

In just because I don't understand what the hell is going on here.

 

[Viper98912]

In the event of a fire? That's some mighty thick concrete there that should resist the fire, no?

I thought sheetrock was just a time-dependent deterrent; in other words, it's fire rated for X minutes for you to escape the area or increase the amount of time for you to extinguish the fire; I don't think sheetrock is permanently a real/full fire stop.

I guess I don't understand what you're trying to do here, if you're looking for a fire stop. That concrete wall is pretty impressive.

 

[exalted512]

Well, this post took some turns from what I originally asked, haha. All good. I responded to most everyone directly, but others I would be repeating myself.

This panic room is outside? Or it's in the basement of the not built house?

House is being built. It's on the first floor, no basement.

Floor drain for dehumidifier?

Why do you need drywall? Fire rating or just make it pretty? If the later can you skin it with Hardie panel?

Yes, there's a floor drain and also conduit in the floor to bring in data and electrical

What are you using for a door that will be fireproof?

Fort Knox brand vault door

Looks like a house is being built around it

Correct.

Not an expert, but the R value of drywall is less than 1. I don't see it insulating well against heat, could be way off base. I would think steel studs, insulation. Fiberglass w/o paper? Then drywall on the inside would be best to keep contents safe. And maybe a Halotron sort of extinguishing system IF things really get out of control.

The point of the drywall is for it's properties as it is exposed to fire. Someone else mentioned a little bit about it here. This particular design was taken from someone that specializes in this type of construction. I don't know all the ins and outs don't want to regurgitate what he told me because it was over a year ago and I don't want to spread misinformation. But essentially, true insulation on the outside won't help because it will burn, whereas the drywall won't (at least, not as quickly). There is a lot of research that I've read to confirm these properties, but as I mentioned, this was all over a year ago at this point and I have since forgotten. But feel free to Google gypsum board fire properties as it relates to thermal transmittance and stick with the research gate or Google scholar articles.

A quality fire safe will cost thousands less and do a much better job.

I would just plaster directly over the surface. Skip the drywall entirely - it's useless here.

Thanks. Know where I can get one that is 88sqft?

If you are expecting drywall to prevent damage to items inside that room with concrete walls, you have more important things to worry about.

I'm guessing those walls are 8" thick walls?

See above about the drywall. Yes, 8" walls, 10" ceiling.

Your thread title talks of applying drywall on the interior of concrete walls. Yet your text talks of doing the same on the the exterior of said concrete walls.

Quote " To help in the event of a fire, it was recommended to have double-stacked fire-rated drywall on the exterior of this room."

Sorry, but I'm not understanding what you're trying accomplish.

It is an interior room. But the drywall will be placed on the exterior of the room.

@ rlitman Thank you the the info, then my thought (even for the wrong reason) would be better than drywall on the OUTSIDE of the shelter/safe.
EDIT: I just looked at the pic again. I meant the steel studs insulation and drywall on the INSIDE. I see wood studs inside, I THINK replace that w/ steel. ON the exterior, for smooth painting surface I would go with plaster directly troweled over the concrete, it might be hard to find a good plaster guy (or gal) then drywall glued up would e 2nd choice.

Good eye. The wood forms were still in when this picture was taken. They will be replaced with steel.

FYI: Unless there is some flammable liquid -- house fires in a basement don't get that hot ... unless part of a mass fire. I have had two major fires and water does more damage .... don't know what the OP wants to save. Even my rural one that took quite a while to put out -- the stuff the basement was just wet

No basement here.

Sure doesn't look like a basement to me.

Correct.

In just because I don't understand what the hell is going on here.

So, um, I was asking if it's okay to mount drywall directly to concrete if the room shares no exterior walls.

In the event of a fire? That's some mighty thick concrete there that should resist the fire, no?

I thought sheetrock was just a time-dependent deterrent; in other words, it's fire rated for X minutes for you to escape the area or increase the amount of time for you to extinguish the fire; I don't think sheetrock is permanently a real/full fire stop.

I guess I don't understand what you're trying to do here, if you're looking for a fire stop. That concrete wall is pretty impressive.

Sorry, I didn't explain what I was trying to accomplish with this room very well because, well, it wasn't really relevant to the question I was asking (can drywall be mounted directly to concrete in this scenario). In a fire, you have four main elements that destroys stuff: the fire itself, heat (but no contact with fire), water, and smoke. You're right that the concrete will act as a great fire barrier. Unfortunately, for the duration and temperature of a house fire, there's a possibility that the heat transfer could damage some of the items inside (this isn't for people). Some of the properties of fire rated drywall will help reduce that heat transfer.

 

[NUTTSGT]

You want to add drywall to the "exterior" of the concrete. I did miss that because of the comment about the room being interior.

So the room is interior to the house with no exterior walls.

Yes, the drywall will add protection to the concrete even if applied directly to it. Any airgap you can create will be better than directly on it. However, it sounds like nothing was left for the airgap or attachment of the drywall. You make do and move on.

As far as the interior, sounds like you have a good door picked out for the room. S slight curb poured in the concrete as you have a "poured on slab" home. . . From what I understand. The curb would prevent water intrusion from firefighting efforts.

So let me ask these questions. Do you live in a populated area with neighbors ? Do you have a full time fire department, combination dept or full volunteer dept. If its the latter, what is their response like ?

Your best bet is smoke detectors, a monitored alarm system and if you have a fire, let the OIC know. If they don't make entry and fight it hard from the yard, they need to keep water on that concrete box.

 

[mike93lx]

Considering the rest of the house needs to be built around it, you have a while before you can hang drywall anyway. I would do it last, to give as much time as possible for the concrete to dry.

Densglas feels like a good suggestion, but I don't know how well it finishes. If it accepts plaster, maybe that would work.

 

[Viper98912]

So you're trying to stop heat transfer?

Put some big heat sinks on it

 

[yeldogt]

Sure doesn't look like a basement to me.

I should have said something above ... it's sitting on the slab. He is calling it a storm room ?

 

[yeldogt]

Where are you in relation to the fire department? -- fire would have to be intense and long to get high heat though all that concrete.

I have always been told that 5/8 was 20min --- but 20min of what. The door is the bigger problem .... gyp is used because it's inert and cheap.

My last fire was back in 12 and it was an odd one -- the fire started outside (tractor) and set my vehicles on fire So the fire had a source that would burn hotter than wood -- fuel. It was also a wood structure with wood siding and roof --- interesting in that the fire burned through the wood windows but since the house was foamed ... there were no passageways for the flames to cut into the framing. It burned like a big marshmallow.

Attaching the drywall to the concrete is all about moisture -- if it's dry you will have no problem. You could always use a latex sealer to delay transfer. As long as it will face a dry area it should be fine

 

[mike93lx]

I should have said something above ... it's sitting on the slab. He is calling it a storm room ?

What's wrong with calling it that? Above ground tornado shelters are not uncommon

 

[exalted512]

You want to add drywall to the "exterior" of the concrete. I did miss that because of the comment about the room being interior.

So the room is interior to the house with no exterior walls.

Yes, the drywall will add protection to the concrete even if applied directly to it. Any airgap you can create will be better than directly on it. However, it sounds like nothing was left for the airgap or attachment of the drywall. You make do and move on.

As far as the interior, sounds like you have a good door picked out for the room. S slight curb poured in the concrete as you have a "poured on slab" home. . . From what I understand. The curb would prevent water intrusion from firefighting efforts.

So let me ask these questions. Do you live in a populated area with neighbors ? Do you have a full time fire department, combination dept or full volunteer dept. If its the latter, what is their response like ?

Your best bet is smoke detectors, a monitored alarm system and if you have a fire, let the OIC know. If they don't make entry and fight it hard from the yard, they need to keep water on that concrete box.

Yea, the air gap was something that I had told the original builder (who was also the architect) and that was just a small change, so we didn't adjust the plans accordingly because he was so busy. He had made note of it in his file for that room, but that was it. He ended up being so busy and we are so remote that we had to go with a different builder and I've been so busy that I completely forgot about it until it was too late. It's surrounded by two showers (that are recessed into the slab) and the stairwell. None of those things can move at this point. So directly on the concrete it is.

I thought about the curb, but water isn't really going to be an issue. Even if water enters the room, it'll be minimal and nothing will be on the ground or have the ability to wick up something that I don't want wet.

I'm not really worried about the heat if the fire department responds. We are very rural and our FD is completely volunteer. If they get to the house in 25 minutes, the room will be fine. What I'm most concerned about is in a wildfire situation where they just let it burn to the point where it would just put itself out. We experienced (secondhand) the effects of the Bastrop fire a few years ago in Texas and we live in a geographically similar area where this is a possibility. Especially since this is our "forever" home.

Considering the rest of the house needs to be built around it, you have a while before you can hang drywall anyway. I would do it last, to give as much time as possible for the concrete to dry.

Densglas feels like a good suggestion, but I don't know how well it finishes. If it accepts plaster, maybe that would work.

Unfortunately, this has to be done reasonably soon. There's a significant amount of framing that is next to the room, so the drywall for this specific room would have to go up before that.

So you're trying to stop heat transfer?

Put some big heat sinks on it

There's an idea! Although heat sinks typically work with an internal heat source and the heat sinks facing out to the ambient air. Having a heat sink on the inside dissipating heat into the spot where I don't want heat to be dissipated might not work. I like your train of thought though! haha

Where are you in relation to the fire department? -- fire would have to be intense and long to get high heat though all that concrete.

I have always been told that 5/8 was 20min --- but 20min of what. The door is the bigger problem .... gyp is used because it's inert and cheap.

My last fire was back in 12 and it was an odd one -- the fire started outside (tractor) and set my vehicles on fire So the fire had a source that would burn hotter than wood -- fuel. It was also a wood structure with wood siding and roof --- interesting in that the fire burned through the wood windows but since the house was foamed ... there were no passageways for the flames to cut into the framing. It burned like a big marshmallow.

Attaching the drywall to the concrete is all about moisture -- if it's dry you will have no problem. You could always use a latex sealer to delay transfer. As long as it will face a dry area it should be fine

Agreed, but that's the type of fire I'm most concerned with. If the VFD comes as it would normally, I won't have issues. It's in the event of a widespread wildfire that concerns me. This happened a few years ago not too far away in Bastrop, TX. We're in an area with similar conditions - mostly rural pastures, subject to high winds, farming community, lots of pine kindling.

Also agreed that the door is the biggest issue. The most heat intolerant items will be placed opposite that wall. We also learned some lessons from the Bastrop fire. Masonry houses with metal roofs and clean gutters (no pine needles) seemed to fair the best. We're mostly surrounded by grass, so no pine needles. The garage is also detached, but connected by a roof. Interesting point about the foam. Our house will be foamed as well. I've been toying with the idea of foaming the inside of this room, but haven't completely decided on that yet.

 

[mike93lx]

Maybe a layer of rainscreen between the concrete and drywall? Can you leave the top without drywall for a while to allow it to dry more?

Slicker® HP Rainscreen | Benjamin Obdyke

Designed for use in exterior wall applications, Slicker® HP is a versatile moisture management system featuring a water-resistant barrier and detachable rainscreen.

benjaminobdyke.com

 

[NUTTSGT]

Also agreed that the door is the biggest issue. The most heat intolerant items will be placed opposite that wall. We also learned some lessons from the Bastrop fire. Masonry houses with metal roofs and clean gutters (no pine needles) seemed to fair the best. We're mostly surrounded by grass, so no pine needles. The garage is also detached, but connected by a roof. Interesting point about the foam. Our house will be foamed as well. I've been toying with the idea of foaming the inside of this room, but haven't completely decided on that yet.

It sounds like you are trying to cover your bases. Keep in mind, heat directly radiated from that door will find something basically in line of site. Think of the way the Sun warms something up, get out of direct sunlight and there's a big difference. So putting something on the opposite wall may not be the best option.

What may help is single curtain hung in front of the door, kind of like a shower curtain. Something made of a radiant material and simple. Even something like Reflectix foil bubble should stop the radiate heat trying to come through the door.

The spray foam, I'm not sure if that is a good idea or not. If it gets hot enough, I don't know if it will off gas or what it off gases. I also don't know what you are storing nor is it any of my business. So I would be leery of what off gases and how it affects what you are storing in that room.

 

[yeldogt]

Fires are really weird .....

I'm a big foam guy and the closed foam does not burn under normal conditions. I have tried to light it and have tried to burn it with a torch -- it will flame a tiny bit but it does not support fire. I have done this with all of my projects -- tried burning it. There are people on the internet who talk about the dangers of foam -- chemicals coming off the burning foam and there are a couple of a flash over building. Well if you light a barrel of flammable liquid inside a foamed metal building w/o any windows or doors. You made a big green egg -- it's eventually going to get so hot .. it blows up.

In reality -- you want to get out of the house fast as possible. The smoke from the initial fire is going to get you -- and that's not coming from the foam. In fact the foam stops the flow of smoke .... on my last multi story traditional house I had the floor of the 2nd floor encapsulated and the two walls off the hall done so that any smoke from the lower levels would only have the stairways to fill the house and hall. This would allow the bedrooms to be isolated.

You say you don't have the space anyway --- but, doing a rain-screen would only be a pathway. I guess you could do it with metal -- using wood would only allow something to burn right against the wall -- and the gap allow for O2 combustion. I'm not sure that gap does anything positive.

Sprinklers are always an options ..... the funny thing about sprinklers. They work .... but, my friend who was forced to install them when he rebuilt a house in PA -- to the tune of 50k about 10 years ago. His insurance company had a higher rate for some valuables as the heads can malfunction and cause water damage

 

[exalted512]

It sounds like you are trying to cover your bases. Keep in mind, heat directly radiated from that door will find something basically in line of site. Think of the way the Sun warms something up, get out of direct sunlight and there's a big difference. So putting something on the opposite wall may not be the best option.

What may help is single curtain hung in front of the door, kind of like a shower curtain. Something made of a radiant material and simple. Even something like Reflectix foil bubble should stop the radiate heat trying to come through the door.

The spray foam, I'm not sure if that is a good idea or not. If it gets hot enough, I don't know if it will off gas or what it off gases. I also don't know what you are storing nor is it any of my business. So I would be leery of what off gases and how it affects what you are storing in that room.

Trying to cover all bases is exactly what we're trying to do. We have the opportunity to, within reason, do exactly what we want from scratch. But we also don't plan on doing this again. Nothing will be perfect, but if we can prepare for as many things as we can on the front end, we're trying to do that.

Interesting point on the heat radiating from the door.

And yes, off-gassing, when exposed to extreme heat, is something I'm worried about, which is why I'm unsure. I think it might be fine, but I haven't got to that point yet. I've actually been leaning towards cellulose the most - but still preliminary.

Fires are really weird .....

I'm a big foam guy and the closed foam does not burn under normal conditions. I have tried to light it and have tried to burn it with a torch -- it will flame a tiny bit but it does not support fire. I have done this with all of my projects -- tried burning it. There are people on the internet who talk about the dangers of foam -- chemicals coming off the burning foam and there are a couple of a flash over building. Well if you light a barrel of flammable liquid inside a foamed metal building w/o any windows or doors. You made a big green egg -- it's eventually going to get so hot .. it blows up.

In reality -- you want to get out of the house fast as possible. The smoke from the initial fire is going to get you -- and that's not coming from the foam. In fact the foam stops the flow of smoke .... on my last multi story traditional house I had the floor of the 2nd floor encapsulated and the two walls off the hall done so that any smoke from the lower levels would only have the stairways to fill the house and hall. This would allow the bedrooms to be isolated.

You say you don't have the space anyway --- but, doing a rain-screen would only be a pathway. I guess you could do it with metal -- using wood would only allow something to burn right against the wall -- and the gap allow for O2 combustion. I'm not sure that gap does anything positive.

Sprinklers are always an options ..... the funny thing about sprinklers. They work .... but, my friend who was forced to install them when he rebuilt a house in PA -- to the tune of 50k about 10 years ago. His insurance company had a higher rate for some valuables as the heads can malfunction and cause water damage

We thought about sprinklers, but found them to be not cost-effective enough to make a difference for our needs. We're more concerned about external fires than internal. An internal fire is statistically more likely to happen, but in that case, the fire department would come out.