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Discussion Starter #1
I am getting ready to begin construction on basement HT. (Looks like I can squeeze out about 15' X 25' X 94" for this project) House is 2 years new. Basement floor does show several "spiderweb" hairline cracks - it has been my experience that no basement floors are without some type of cracks (at least in Central Missouri). I was looking for some help with in the following areas:

  1. Did you do anything with your cement floor before starting project ? (Radonseal says use their product - Drylock says use theirs - several books say put down a layer of plastic then build a 2X4 laid on side subframe, then add rigid insulation and finally 3/4" plywood on top)

  2. Are any of you who didn't do anything beforehand having any problems after completion with moisture, dampness, mildew, etc?

  3. Those of you that did do something beforehand - would you do it different in hindsight? (which we all know is 20/20)

  4. Is it absiolutely neccessary to nail into basement floor (masonry nails, screws, etc) or can I get by with something like liquid nails?

  5. Have any of you built out rooms in this general size and is it sufficiently large enough? (IYHO)

  6. I am still struggling with dedicated room (fully enclosed) vs multi use room (back end open). Any thoughts on this?
I don't think that I am going to get "really ****" on this project (but that could change down the road). I initially feel like I just want a room that I can watch high quality Video and have good sound.

Been kinda reading through many of your threads over the last couple of weeks and thought I should probably try and tap the "braintrust" here as experience has shown it is way better than trying to reinvent the wheel each time. Thanks very much in advance for your help.:reading:
 

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Hello, and welcome to the Shack!

There are so many different so called sub floor systems that its tough to say what is best. If you live in an area that has a high water table and your basement gets damp a sub floor is not the only thing you should be putting down. You should be putting down some sealer and paint it on the floor to also help with moisture blocking.
I helped a friend put down panels of 2'x2' sub flooring that locks together that also has the insulation and vapor barrier mounted on the underside of the panel. This makes the installation easy and also gives you a nice surface to lay down carpet on.
My basement had the old VC tiles on top of the cement floor and has several coats of wax on top of that so it already had a good seal so all I did was put down underlay and carpet on top of that. Have had no issues so far and its been a year.
The basement is 15'x 37' and works very well as a multi use room.
 

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Discussion Starter #3
Maybe I should note that I have not had an issue with dampness (up to this point). The foundation is fitted with drain tiles athat run into a sump pit. The sump pump then pumps up and out into an area away from the house out in back. The system seems to work quite well (almost to well as it runs quite a bit during rain storm).

Also I did see the OVRX panels on their website. It appears to run about $5.00 per square foot to install a system such as that. I would be looking at somewhere right around $2000 for that. Seems like a waste if it is not needed (but a lifesaver if it becomes an issue down the road). what to do what to do what to do
 

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Here is my semi basement build while it was being dug out in missouri. We hit some beadrock. There is zero moisture on the concrete floor. There is a drain above beside a garage that if gets stuck with leaves there is some slight mositure in one area due to the trapped water. It has survived many ice storms and floods etc. We have a very extensive underground irregation system in the yard that channels it all into the lake.

I used liquid nails to reinforce my studs that were very close to the walls, but I am not certain this is always good practice.





Please excuse the mess. This was taken while some insulation was being moved around.







There is still more to be done. Replace the old speakers, get some more gear, more treatments, and so on.

You can see here after a couple years the concrete was dry when I was adding some insulation to my stage area last week. The kraft paper looks a little damp, and I felt some older insulation in an area in the back of the room that felt kind of oily to the touch, but not damp.

 

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Here is a photo of the moisture problem durring a three day flood (other areas) while the drain was backed up directly above the HT.

 

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The kraft paper looks a little damp, and I felt some older insulation in an area in the back of the room that felt kind of oily to the touch, but not damp.
This is a direct result of condensation. If your cement floor or walls are cold and your interior is warm you will get moisture build up on the surface. This is why a good sealer and vapor barrier with insulation is so important.
 

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Our builder said it would cause more harm than good. The area is treated lumber, will it be alright? Room is done in indoor/outdoor carpet no pad. Imprevious to water.

Edit:

Other side of the screen wall in now dug out and the driveway water was diverted to another location by adding more concrete. The deck above the earth outside the screen wall is now waterproofed featuring drainage (plastic tile with ridges, excatly the same that I used in the HT on the sides except not painted) and it's own gutter system.
 

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The area is treated lumber, will it be alright? Room is done in indoor/outdoor carpet no pad. Imprevious to water.
It should be for some time to come but even treated lumber will eventually mildew if it stays damp for too long. any contact with a cement floor or wall should have a plastic strip between the wood and the cement to help avoid moisture from seeping into the wood. the indoor outdoor carpet should be fine as long as it has a chance to dry fairly quick and doesn't stay wet for days.
 

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:praying: Please lumber last until HT 3.0. The wood is in contact with cement at the floor with nails into the concrete. There is also some lumber in contact with some steel in the ceiling.
 

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The foundation is fitted with drain tiles that run into a sump pit.
I have the same setup as you. I have carpet on cement and have had no moisture problems in the 10 years the basement has been finished. When I started to finish the basement I was told by a contractor to place a big piece of plastic on the cement floor and leave it for a few days, then lift it up and see if there was any moisture. In my case there was none.
 

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Welcome Lonnie!

I don't have moisture problems in my basement. It's a daylight basement, so the entire back of the basement is at grade. The front of the basement is poured wall 12' high.

I built our dedicated HT in the front side of the basement. I studded out with treated lumber plates attached with a combination of masonry nails and construction glue. The nails were the type driven by .22 charges.

Before laying down the carpet pad, the installers put down a layer of roofing felt. The salesman @ Home Depot recommended either that or a concrete sealer. I don't have any regrets going this route. The house is five years old and moisture is not a problem.

In your instance, I would be concerned building up the floor since you don't have much ceiling height. Is the ceiling already finished? I used a suspended ceiling. Armstrong sells black acoustic tiles as well as black hardware. Even with a suspended ceiling, I've got 9 feet. Ceiling height may enter in your plans for a projector, assuming you're planning FP. The goal is to mount the projector absolutely level. Some projectors have such an offset that an 8' ceiling would place the image too low.

Your room dimensions sound fine. If you're planning on front projection, I urge you to make it a dedicated space with complete light control. Even a small amount of uncontrolled ambient light can degrade image quality.

Make all wiring runs (speakers, etc.) conduit to allow an easy reconfigure/upgrade. I assume your depth is 25'. You might consider putting an equipment closet in the back. Our HT adjoins a 10x12 storage room. I built a platform in the storage room, built an opening into the HT and put in an equipment rack. It's great to be able to just walk in the storage room to access the back of the components.

Have fun and keep us posted! We'll be happy to answer any other questions that may arise.
Doug
 

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Welcome!

Here is my photo journal of my basement build from start to finish:

http://www.itsallbutstraw.com/gallery2/main.php?g2_itemId=5341

We have a high water table, and never have a damp floor. It does get humid down there so I run a dehumidifier 24hrs I used some simple felt type carpet so that it breaths well, its black and suites my needs. I try to keep the hum level around 55-60%. I had my studs nailed to the floor, but maybe should have glued them. I used the pink insulation on all the walls, but did not use a vapor barrier, my thinking and the contractor's thinking is that the paper backing on the insulation will server as a vapor barrier, and will still allow some air around the walls, also the three concrete walls the studs were held back from the wall about 1/2-3/4" to provide a gap, where the insulation is not actually touching the concrete.
 
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