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PostPosted: Tue Jul 23, 2019 5:20 am 
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Hello,

First post here, seems like a great community and I'm glad I finally registered.

So I decided to build a studio in the basement of my house. The basement is 7m long, 3.2m wide, and 2.2m high. The basement has concrete walls, concrete ceiling, and concrete floor.

However, I am a bit stuck on how I should optimise the floor. Let me elaborate:

The basement is in a earth sheltered house.

Today, my floor is laminate flooring, underneath that we have a 2mm plastic sheet, then OSB wood, then a gap of air before we reach the actual concrete. When I walk on the floor, it gives of a bassy drum like sound, almost like what a T-Rex footstep sounds like. :D

As you can imagine, when I try my speakers in this room the bass drum drowns the rest of the elements in the track due to the described problem. My guess is that this is caused by the fact that there is a gap of air between the OSB (correct me if I'm wrong).

So I've been looking at changing the floor so optimise it for my studio. However, from what I've understood it is essential for these types of houses to have this "gap/space of air" between the concrete ground and the wood to prevent any moisture to reach the wood and to let water pass under the house.

I searched this forum and found different answers, some people suggest to fill the floor with sand, others say you should use mineral wool.

Neither of these solutions seem to fit because apparently the gap of air needs to be there to prevent damage from moisture. Is there some way around this? How can I solve my problem?

Appreciate any help!


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PostPosted: Tue Jul 23, 2019 5:38 pm 
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Joined: Sat May 20, 2017 7:47 am
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Location: Surfleet, UK
Hi Sammyk,

That sounds like a strange design you have there, usually a damp proof membrane would seek to protect the floor, how would it do that between the laminate and OSB?? :shock:

You would be able to get advice from building control in your location for appropriate basement floor treatments but I can give a little advice.

The reason it sounds boomy is because of the undamped air gap yes. A concrete slab is the best floor for a studio.
I don't know if anywhere in the world that requires an air gap for rising water. Although it could depend on the age of your slab.
Back in the day people would have an air gap and a wooden floor on joists and vent the cavity underneath, but that was only for old buildings built prior to good damp proofing designs.
Some people also use it to make the floor less cold when walking on it with bare feet.

Your best bet would probably be to take out the wooden floor. Place some concrete slab insulation, a polythene damp proof membrane, and pour concrete again. This would be your final finished floor (you can put laminate flooring with underlay directly on top of this if you want).

If you're worried contact building control and ask their advice.

Dan


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PostPosted: Wed Jul 24, 2019 12:01 am 
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Joined: Tue Jul 16, 2019 1:15 am
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Hey Dan,

Thanks a lot for the reply.

There was a water pipe incident which damaged the floor before we bought it, it's an older house from '73. So apparently the water pipe broke causing water to gather underneath the basement floor.

We don't know who the contractor was or what he exactly did, but he decided to leave a gap of air there to prevent moisture damage, a type of ventilation system for the floor.

Quote:
That sounds like a strange design you have there, usually a damp proof membrane would seek to protect the floor, how would it do that between the laminate and OSB??


I think there might be a damp proof membrane underneath the OSB as well but we haven't checked yet, thing is, I don't want to ruin the floor before knowing what I'm going to do about it. I'm afraid to cause damage to the house if I do anything at this point. I have contacted a damp expert and they are looking at what my options would be, but I figured this forum might have some advice as well.

Quote:
Your best bet would probably be to take out the wooden floor. Place some concrete slab insulation, a polythene damp proof membrane, and pour concrete again. This would be your final finished floor (you can put laminate flooring with underlay directly on top of this if you want).


Would the damp proof membrane have the same function as the void of air or is it risky in these types of earth sheltered houses, or might it cause damage doing this? I have attached a picture of what the floor might look like, although I'm not sure the contractor did exactly as the picture shows.

Just off the top of my head, would it help if I keep the floor as it is (including the void of air) and build another floor on top of the current floor, and fill it with mineral wool?

Would appreciate any suggestions.


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PostPosted: Wed Jul 24, 2019 8:35 am 
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Joined: Sat May 20, 2017 7:47 am
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Location: Surfleet, UK
I'm not experienced with earth sheltered housing, but the image you attached doesn't seem to match how your floor would be constructed. Are you certain that design is used for an earth sheltered home?
I was under the impression the walls are covered almost entirely with earth, therefore your ground level would be the entire height of your wall and wouldn't allow the under floor cavity to be ventilated from outside, as in the picture.

If it is actually ventilated like that though you may have problems. If it is required to keep it ventilated you can't fill it with anything. With a suspended floor like that your only real option would be to replace it with concrete, or you will always have resonance issues.

The way I would do it: carefully remove the laminate flooring. Replace the timber joists and OSB with a concrete block and beam floor. Then pour a concrete layer over the top of this to create a sealed concrete slab. You can then put your laminate flooring back down on this.

This would give quite good isolation, but depends on the rest of the room being all isolated. The resonant frequency would be significantly lower than the current floor.
How much isolation (in dB) do you need? Also what are your plans for the rest of the room?

Dan


****EDIT**** I just reread your first post. You mention your have a concrete floor underneath the timber, and concrete walls too. It's almost certainly not ventilated to the outside then. There doesn't seem to be any reason why the floor is suspended. The concrete floor and walls should all be protected by damp proof membranes to prevent water ingress.
The only water inside the room would come because of damaged membranes, burst pipes or internal condensation. But all of those can be remedied without a suspended floor.

In any case you can't use an undamped suspended timber floor in a studio.

If I were you I would remove the laminate flooring carefully and store it. Then pull out the timber floor. You have a concrete floor underneath (you said that right?).
This is your new floor. If the damp proof guy has a problem with this (and provides evidence that this will really be a problem) then you will be suspending a concrete floor anyway, not a timber one. So you haven't lost anything in looking.

Dan


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PostPosted: Sun Jul 28, 2019 7:00 am 
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Hey again,

Thanks a lot for putting your time into answering and thanks for your suggested solution.

I finally pulled out a bit of the floor and OSB to see whats underneath.

Theres laminate flooring, OSB, mineral wool, then what I assume is the damp proof membrane. Underneath that is the concrete. So perhaps the damp thing is fixable in the way that you described.

Unfortunately there is another concern (I don't know if this is a problem or not). This house has a radon decontamination system (a radon extractor) being that it's built upon radon active ground. So the pipe that extracts radon goes into the floor of this basement. Can this be a reason why there needs to be an air gap? I don't know how the piping looks down there. But regardless, would this cause a problem with filling the floor? A saftey hazard?

I'm thinking maybe we could pour concrete everywhere but where the pipe goes, but I'm not sure if it could cause problems with the system. Fingers crossed it won't be a problem, what do you think?

I took some pictures if you want to take a look. I really appreciate the help.

https://imgur.com/a/ByCU6Pd


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PostPosted: Sun Jul 28, 2019 8:00 am 
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This is starting to make a little more sense now. Found this in a google search:

https://www.corroventa.com/news/2018/10 ... amination/

Quote:
In crawl spaces you have to combine ventilation and dehumidification. If you only use ventilation you will get problems with moisture and mould in the future as you suck warm, moist air inside the crawl space which cools down and increases the level of humidity. The machine installed will produce under pressure in the ground and prevent the radon from entering the house. You have to make sure that the crawl space is sealed, otherwise the radon will manage to enter the house


So thats it then? Nothing I can do about it? Or maybe I can fill up the crawl space as written in the above post?


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PostPosted: Sun Jul 28, 2019 10:56 am 
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Location: Surfleet, UK
sammyk wrote:
This is starting to make a little more sense now. Found this in a google search:

https://www.corroventa.com/news/2018/10 ... amination/

Quote:
In crawl spaces you have to combine ventilation and dehumidification. If you only use ventilation you will get problems with moisture and mould in the future as you suck warm, moist air inside the crawl space which cools down and increases the level of humidity. The machine installed will produce under pressure in the ground and prevent the radon from entering the house. You have to make sure that the crawl space is sealed, otherwise the radon will manage to enter the house


So thats it then? Nothing I can do about it? Or maybe I can fill up the crawl space as written in the above post?


As soon as you mention radon, you need the pros. Don't touch your floor. The website says that there's different designs for basements etc. Get the radon guys in. Seriously. Get them to tell you exactly what you need in your floor for safety. Then ask them about a concrete floor.

I can't give any other advice than that I'm afraid waaaay out of my expertise.
Dan


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