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Old 01-15-2009, 11:43 AM   #1
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basement framing and insulating


I'm trying to figure out the best way to frame and insulate the outside wall of my basement. First of all I have a 4 ft foundation wall with a 3 inch lip on top where the brick starts and goes 4 ft to the floor above. The foundation wall is 1 inch wider on bottom than the top and is bowed 2 inches inward in the middle of a 52 foot span. I am trying to stay away from using 2 X 4s beacaue it will eat up too much space.I was thinking of glueing 1 inch rigid foam insulation on the brick. I would build a short wall of 2 x4's the 3 ft from top of foundation wall to the joists above and insulate with faced fiberglass batts. Below I would attach 2 inch furring strips 16 inches o/c with concrete nails and add 1-1 1/2 inch rigid foam between strips. Because of the bowed wall there may be some playing around with shims to get everthing straight. Do I need to leave a gap between the foundation or brick and where the new wall starts?

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Last edited by Donbee; 01-15-2009 at 11:48 AM.
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Old 01-15-2009, 01:28 PM   #2
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The rule is to have a one inch gap behind the fiberglass batt insulation and at the brick and/or concrete.

Use pressure treated lumber where contact with concrete floor, foundation, or brick may occur.

Check your city's building code for R-value needed, for example R-19 over the portion of wall above grade and R-13 for portion of wall below grade.

Where the outside of the foundation has been coated with waterproofing, there should be no vapor barrier in the newly constructed finish wall.

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Old 01-15-2009, 09:44 PM   #3
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I thought you wanted to stay away from 2x4 walls? Why do you want the thicker wall on the top half (is that 3ft or 4ft of brick wall)?

Depending on where you're from??....you could just adhere the foamboard directly to the walls (caulking and taping all the seams), then place the furring strips on top of the foamboard (24" OC, fastening to the wall) and then cover with sheetrock (your fire barrier). You might want to keep the sheetrock an 1" of the floor or so.

You'll probably want to snap yourself a chalk line on the floor (3,4,5 method) and square it up. Perhaps you could use furring strips of varying thicknesses to keep it straight??

This method is the latest I'm considering in doing my own basement. Seems cost effective, less time consuming, using less space, as well as energy efficient. I too am considering the use of high density foamboard on the floor as added insulation, covering with 5/8' plywood as a subfloor.

Best of luck.
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Old 01-15-2009, 09:50 PM   #4
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basement framing and insulating


I suppose I should give in and use the 2 x 4 framing. It seems like it would be much more easier than the alternative. I might be able to rip some lumber where the wall is bowed so I don't lose all that space.

My house is over 60 years old and there is any waterproofing on the outside of my foundation, there's no tar or anything. I sealed all the cracks with a 2 part epoxy injection which has solved my water problems for now. I still would like to seal them from the outside at some point as a precautionary measure.

There is a vapor barrier on the faced insulation and I don't think it's necessary with the rigid foam or is it?
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Old 01-15-2009, 09:59 PM   #5
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The recent advice I received is that if I build a 3 ft wall on top of the foundation and then furring strips on the foundation underneath I run the risk of that dry wall seem cracking up because it is not a continuous, so I go to the 2 X 4's. I would like to keep everything 16 o/c for uniformity and easier insulating.
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Old 12-23-2010, 02:42 AM   #6
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I'm also considering insulating my basement. But I was considering 2x4s and mineral wool (3 1/2" ROXUL) since mineral wool is impervious to water. No condensation problems and minimized damage in the event of flooding.
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Old 12-24-2010, 12:20 AM   #7
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Mineral wool is far better than 'glass, for sure. Never use 'glass against a concrete wall. IMO, never use fg batts ANYWHERE. No vapor barrier below grade, but a vapor retarder and GOOD air sealing is critical. Read on buildingscience.com for details.
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Old 12-24-2010, 09:07 AM   #8
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Quote:
Originally Posted by jklingel View Post
Mineral wool is far better than 'glass, for sure. Never use 'glass against a concrete wall. IMO, never use fg batts ANYWHERE. No vapor barrier below grade, but a vapor retarder and GOOD air sealing is critical. Read on buildingscience.com for details.
I know BS says that, but that would never pass a building inspection here.

I really don't understand these questions all the time. The IRC code book, which most of us MUST comply to has all the answers, and is online also. Are there this many people that never pull permits or have inspections?
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Old 12-24-2010, 01:05 PM   #9
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"I know BS says that, but that would never pass a building inspection here."----- that would be in Minnesota, you must be talking about a new basement, after 2009?

Page 32: Tips for Remodeling Basements
You DON’T need insulation, an air barrier, nor a vapor retarder on foundation walls or crawl space walls when you finish an unfinished basement or remodel an existing finished basement. The ONLY exception is for houses built after June 1, 2009 to the new energy code requirements. This code change was proposed by BAM because our remodeler members asked us to “get rid of the poly” requirement for basement walls. Since adding insulation in a wet basement can cause serious moisture problems, the requirements were removed to help remodelers adjust their insulation and water management strategy to each individual remodeling job. So for an older basement, you have five options:
A) Leave the existing insulation system in place and finish the walls.
B) Remove the existing insulation system and add a new system of your choosing.
C) Add an insulation system of your choice to an unfinished basement wall.
D) Leave the basement uninsulated.
E) Don’t take the remodeling job in cases where the homeowner won’t pay for a finished basement that will be both warm and reliably dry.
In summary, build a foundation system that works for your homeowner. You can certainly use the new construction wall foundation specifications or modify them to fit the needs of the specific home or create your own system. (See BAM Illustrations #7 – #18). The building inspector has no jurisdiction to inspect the insulation, vapor retarder, and air barrier on remodeled foundation walls built before June 1, 2009. [N1101.1, Exception #2 on page 4 of the code] But they can still inspect to make sure you are meeting the thermal barrier requirements in R314.4 if certain types of insulation are installed. They can also inspect rim joists and above grade frame walls which have to meet the energy code requirements for new construction or at least the entire cavity has to be filled if new construction R-values can’t be met. [N1102.6.5, C on page 28 of the code] http://www.bamn.org/images/energycod...guide-text.pdf


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Old 12-24-2010, 03:28 PM   #10
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You are correct GBR. It is for new construction or additions after the date you posted. The rest of the existing house does not require ANY insulation under the code. The reasoning stated on the IRC page for MN is to.....in short...."save homeowners money" on renovations. Sounds like a good idea.

IMO, if you are finishing off a basement that is not finished at all yet, it should be brought up to code.
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Old 12-25-2010, 04:14 AM   #11
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Quote:
Originally Posted by MJW View Post
IMO, if you are finishing off a basement that is not finished at all yet, it should be brought up to code.
Good point. If for nothing else, getting something up to code means something to the banks, who may finance it later.

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