Basement finishing

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Old 05-19-17, 10:06 PM
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Basement finishing

Hello all,

I've recently purchased a house in Kansas City, Mo which was built in 2015 and am in the process of building a workshop area in the basement. The basement is unfinished, however the perimeter has already been framed/insulated. The framing against the below grade concrete is spaced an inch or two away from the wall with unfaced fiberglass insulation between the studs. There is no rigid foam or vapor barrier between the concrete and framing or on outside of the framing (between frame and eventually drywall). I've been reading a lot of conflicting information online about whether or not to install a vapor barrier prior to hanging drywall and I'd just like to get a clear answer. Do I need a vapor barrier anywhere prior to drywall? Also, should there be rigid foam insulation between the concrete and the framing?

I really don't want to have problems with moisture in the walls down the road, however I really don't want to tear down all the framing/insulation to install rigid foam insulation on the concrete if it's not needed.

Thanks for any advice!
 
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Old 05-20-17, 03:47 AM
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Do I need a vapor barrier anywhere prior to drywall? Also, should there be rigid foam insulation between the concrete and the framing?
Oh boy, for some reason this is one of the most contentious topics I have come across.

Currently the trend is to put foam onto the wall then build your walls. Nothing wrong with this except it can add a big cost impact not to mention the extra work to install.

The issue is moisture in the basement condensing on a warm surface. The foam insulates/seals the walls.

Personally I dont want a sealed basement, I've done many basements by building the walls away from the foundation insulating with faced or unfaced BUT you have to leave open areas above the walls near the rim joist.

This will allow moisture, to vent from behind the walls to the interior space and not become trapped, trapped moisture is where problems will come from.

Now some will say that that is not a fully sealed basement, true, but you have 95% of the area covered and that last 5% is what cause issues.

And, regardless of what system you go with, if you have water problems neither is a cure for that, get them fixed first!
 
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Old 05-20-17, 09:27 AM
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That shouldn't be a problem since I'm only sheet rocking a workshop and plan on keeping the ceiling open anyways. I also have a portion of wall where the concrete foundation is only 5 ft tall, steps in a 2x6, with framing on top. Since I can't really leave a gap in the middle of the wall (top of the concrete) will it be ok to completely close that area off?
 
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Old 05-20-17, 02:09 PM
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Sorry, can you provide a picture, the description is not clear!
 
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Old 05-21-17, 03:05 AM
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Old 05-21-17, 07:41 AM
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I recommend you check with your local code officials; in most areas basement walls must have fire stops at the top of the wall that separate the top of all walls from the floor joist spaces above. The fire stop must be continuous from the top plate of the basement foundation to the inside edge of wall top plates. This may not be an issue if you are not planning to finish the ceiling area, but I wouldn't count on it.
 
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Old 05-21-17, 11:10 AM
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Name:  20170520_112210.jpg
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Size:  25.4 KB

Here is the section I'm talking about, I have about 10 ft of wall like this to finish...the rest is either going to remain unfinished or is all wooden framing.

Sorry for the sideways picture, on my mobile
 
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Old 05-21-17, 07:05 PM
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With insulation on the inside and cold temps outside the exposed upper areas of the foundation will get very cold. Yet the foundation near the floor will remain warmer from the soil outside. This temperature difference sends warmer air up through that gap between the insulation and the foundation where the air can reach the cold surfaces of the foundation and that can result in condensation or frost.

Another issue is not having an air barrier covering the inside of all walls. A vapor barrier is not necessary unless code requires it as leaving it out will allow some drying to the inside. Add the vapor barrier and you increase the moisture level between the VB and the foundation. Not good if the fiberglass is in between.

Use of the rigid foam over the foundation before the framing solves several issues and since the rigid (pink or blue) is a bit permeable it supports that limited amount of drying.

Always difficult to give advice after everything is assembled but the advice remains the same. Check local codes to see if a vb is required, they are often years behind the sciences. Here is a link that may help.
https://buildingscience.com/document...ts?full_view=1

Bud
 
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Old 05-21-17, 10:32 PM
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Thanks for all the advice fellas, I only wish it hadn't all been framed before I bought it...so I could make sure to do it right.
 
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