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Old 05-30-2008, 03:59 PM   #1
JTK
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Vapor barrier requirement for finished basement


We want to finish our basement which is 3/4 length below grade. When we had the foundation poured , be it wise or not, we listened to the foundation guy and did not insist on having foam insulation installed before back-filling. The foundation guy did paint on a tar coat however to meet the minimum requirement I guess. Over the last 12 years, my only problem is rain water seeping through the cracks below the basement windows. This problem is now fixed. We had the basement windows enlarged and put in window wells and crushed stone. The storm drain along the foundation footing was also fixed so that water would not come out from the fitting connections. The contractor had caulked the the tee connections.

Now we want to finish the basement. Although there has been no water table problem, as our house is situated on a slope with the basement at street level, there has been humidity problem as evidenced by a rusting I beam and some iron metal surfaces. To reduce the humidity infiltrate through the foundation walls, what type of vapor barrier measures should we put in. I am planning on putting up studded walls with fiber glass insulation. There are a couple of ideas I could think of as an amateur:

1. Use Thompson water sealant to spray on the concrete foundation and air out the space. I applied it on the concrete floor before and it seemed to have sealed with floor well, as evidenced by water forming droplets when water was spilled on the floor.

2. Put up a clear polyethylene plastic sheet over the concrete foundation wall behind the stud wall, forming a seal from top to bottom.

3. Put up the clear polyethylend plastic on the interior side of the studded wall before sheetrocking.

Advice needed: what is the best way to water vapor proof the basement from the outside, and not trapping moisture that would cause rotting problems later on the wood studs, perimeter joices?
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Old 05-30-2008, 08:27 PM   #2
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Vapor barrier requirement for finished basement


Your best bet is to get a dehumidifier to remove moisture.
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Old 05-31-2008, 07:18 PM   #3
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Vapor barrier requirement for finished basement


When finishing a basement, I like to apply a coat of Drylock to the walls. I would also frame with metal studs , and rock the bottom row of sheetrock with greenboard left off the floor at least an inch.
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Old 06-01-2008, 09:05 AM   #4
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Vapor barrier requirement for finished basement


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When finishing a basement, I like to apply a coat of Drylock to the walls. I would also frame with metal studs , and rock the bottom row of sheetrock with greenboard left off the floor at least an inch.
I think drylock requires 2 coats to be effective.
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Old 06-01-2008, 07:05 PM   #5
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Vapor barrier requirement for finished basement


The problem is that the water is getting in. There's no real way to deal with it once it has already infiltrated through the foundation walls. You need to fix the water at the source before you finish the basement. Putting up plastic to mitigate a moisture problem will create as many problems as it fixes. Thompson's products are not quality products and I'd never recommend them for anything.

Foam insulation wouldn't help you keep moisture out. The black asphaltic spray on the outside of the foundation is the code requirement, although there are some other options these days. The black spray works just fine, until the foundation cracks!

I'd suggest looking into epoxy injection to seal the cracks that are allowing the water to enter the basement. There are several manufacturers, but the only one I can think of off hand is Simpson. Also, you need to install a sump pump if you don't have one. You need to extend your gutters' downspouts, and you need to make sure that the grade next to your house drops at least 6" in the first 10 feet.

A dehumidifier is a good idea once you've finished the basement. But, I wouldn't dare finish that basement until you totally get that water infiltration problem fixed. You'll regret covering it up.
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Old 06-02-2008, 05:10 PM   #6
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Vapor barrier requirement for finished basement


Thank you for everyone's suggestions. Perhaps I should have been clearer. I did have the water leak problems fixed now. The mason dug up the dirt all the way down to the foundation, chiseled out the cracks and filled them with hydraulic cement. He also fixed the storm drain leaks from the tee connections on the corrugated black pipe. He caulked the joints and replaced the parts that was crushed and cracked open by rocks from the back fill. We also have French around the foundation, so the crushed stone will drain the water into the perforated black pipe. We took advantage of this work and had window wells and larger windows put in. The window wells with the higher level now allowed the mason to build up the level of the patio and the surrounding ground level higher to pitch water away from the windows/previous cracks. The foam insulation I alluded to previously was meant for insulation on the outside as oppposed to insulation on the inside of the foundation. So I have heard.

My question now is how to vapor proof the basement from moisture that permeates through the foundation wall. I have seen on TV that people put a plastic vapor barrier over the studs and fiber glass insulation before installing the sheetrock/blue board. I thought this would allow the humidity to get trapped behind the plastic, potentially causing problems with the studs and insulation. So I thought about putting the plastic behind the stud and insulation on the foundation side. The drawback of this option is the humidity trapped there has no way to go except up to the perimeter joices.

I suppose if there is no vapor barrier used, the humidity can permeate through the sheetrock/blue board/green board gradually and would not cause mewdew or rotting problems long term behind the sheetrock.

I will look into the Drylock option.

JTK
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Old 06-02-2008, 06:12 PM   #7
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Vapor barrier requirement for finished basement


Ahhh...Gotcha!

Yes, at this stage, Drylock would be a good idea. I would want to take care of the moisture before putting walls up. Your assumption about humidity and condensation behind the vapor barrier is valid.
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Old 06-02-2008, 09:47 PM   #8
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Vapor barrier requirement for finished basement


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Ahhh...Gotcha!

Yes, at this stage, Drylock would be a good idea. I would want to take care of the moisture before putting walls up. Your assumption about humidity and condensation behind the vapor barrier is valid.
Keep in mind that by making a basement so air tight also can half a detrimental affect where there is no circulation of fresh air which makes it what they call a "sick house."

That's why house wrap is popular. It keeps moisture out while letting the house breathe.

Last edited by handy man88; 06-02-2008 at 09:54 PM.
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Old 06-04-2008, 08:10 AM   #9
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Vapor barrier requirement for finished basement


Drylock is a simple and somewhat effective option. This should help with water permeating through the walls but as someone stated earlier, make sure you use two coats as that will make it more effective. Keep in mind though that should you ever have a water table issue, a drainage system with a sump pump is most likely your best and most effective option.
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Old 10-31-2008, 11:43 AM   #10
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Vapor barrier requirement for finished basement


Well, sure he could do that, but maybe he doesn't have to do anything. If he has a furnace and water heater, then his moisture problem doesn't need fixing during the cold seasons. However, in the summer he has to open up all the basement windows to vent the moisture. Furnace and Water heater vent their exhaust along with the basement fresh air. So, they also vent the moisture. I have noticed that in my basement. They say that your furnace and Water heater needs fresh air intake from outside. Well if you have a moisture problem during cold season, you are obviously going to be running your furnace and the water heater which will take care of the moisture problem.
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Old 10-31-2008, 11:55 AM   #11
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Vapor barrier requirement for finished basement


I'm currently in the process of finishing my basement. Check out this document for what you need to know and how you should complete your project.

http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

You will find endless opinions and recommendations from everyone who have their own ideas and theories. The Internet is a great place; if you can sift through the misinformation to find the facts.
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Old 11-01-2008, 11:50 PM   #12
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Vapor barrier requirement for finished basement


That pdf was a great info thanks.
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Old 11-02-2008, 03:58 PM   #13
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Vapor barrier requirement for finished basement


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Originally Posted by diy4life View Post
Well, sure he could do that, but maybe he doesn't have to do anything. If he has a furnace and water heater, then his moisture problem doesn't need fixing during the cold seasons. However, in the summer he has to open up all the basement windows to vent the moisture. Furnace and Water heater vent their exhaust along with the basement fresh air. So, they also vent the moisture. I have noticed that in my basement. They say that your furnace and Water heater needs fresh air intake from outside. Well if you have a moisture problem during cold season, you are obviously going to be running your furnace and the water heater which will take care of the moisture problem.
I never open my basement in the summer as hot humid air is the main source of condensation in cool basements.
I keep it closed tight and run a dehumidifier!
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Old 02-05-2011, 04:30 PM   #14
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Vapor barrier requirement for finished basement


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Originally Posted by Reilley View Post
I'm currently in the process of finishing my basement. Check out this document for what you need to know and how you should complete your project.

http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

You will find endless opinions and recommendations from everyone who have their own ideas and theories. The Internet is a great place; if you can sift through the misinformation to find the facts.
This is a great link. The information presented in the article makes a lot of sense. The Black and Decker 'Finishing Basements' book has similar recommendations and so verifies the information in the book.
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