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Finishing basement, how to deal with stairs against foundation wall

Finishing basement, how to deal with stairs against foundation wall


  #1  
Old 04-03-11, 10:01 AM
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Question Finishing basement, how to deal with stairs against foundation wall

Hi all, I'm new here, so please bear with me. We are preparing to finish our basement. Our house was built in 1977 and we have lived here for 2 yrs. We are in sand and there have never been any drainage issues or moisture problems in the basement, that we are aware of. We have been doing our reading and are planning on doing the "Full Wall Insulation with Foam Sheathing Covered with Gypsum Board" method using 2" high density XPS (the pink stuff from Menards) for the entire basement. However, the stairs going down into the basement are right up against the foundation wall and we are at a loss with how to best deal with this. Is it okay to leave the stairs against the foundation and build the wall around them? That would leave the wood of the stairs in contact with the foundation wall and I'm not sure if that is considered an okay thing to do? If there is a better alternative, what it is? Also, we don't want to lose very much of the width on the stairs. They are 36" wide right now. Would it be okay to use 1/2" or 3/4" XPS there, attach furring strips to it and then drywall on top of the furring strips? If that is okay, how do we attach the furring strips to the insulation?
Thanks in advance for sharing your knowledge!
Mackenzy
Here is a picture of the stairs:
 
  #2  
Old 04-03-11, 10:37 AM
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Welcome to the forums! While I am not a fan of XPS on exterior walls for the sole purpose of stopping moisture, others on the forums may give different advice. The stairs will be your weak link if you should ever have a problem, and there's no need in doing the remainder of the walls if you leave this area. Water can only be properly stopped from the outside. If your walls are below grade level, you need no insulation as they are goethermally correct to begin with. The temperature won't change more than a few degrees all year long.
I prefer to frame a wall 1" from the wall. Adding insulation is an option. Leaving the space will help dissipate moisture (not water).
Hang in there for some better information that may work in your area.
 
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Old 04-03-11, 11:07 AM
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Thanks for your reply. I suppose it is worth mentioning that we are in Northern WI. We are planning on doing this area. It will be part of the family room. But we were thinking to make a template and cut the XPS to fit around the stairs, if that makes sense. Also wanted to add that the walls are all white, not sure if that is Dry Lok or regular paint or if it even makes a difference.
 
  #4  
Old 04-03-11, 01:36 PM
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As Chandler said--- location, location, location.

For your location, your frost line is 45-55" down. http://www.soundfootings.com/pdf/US_...t_DepthAVG.pdf If 2' above grade, and 4' below grade, that's 6' at close to outside temperature, or 3/4 of the wall at outside temp.. Check the figures and example here; http://www.quadlock.com/technical_li...Insulation.pdf
It would be silly to lose that much heat for 3/4 of the wall when only the bottom portion is temperature stable (below the frost line). Other parts of the Country are different which is why there are many different answers due to local conditions. I wonder how many thousands of hours are wasted because locations are not specified in first post.

The stairs; you would need to ask your local B.D. as they may be required 3' wide for part of the path of egress; Chapter 3 - Building Planning
The insulation is important as well, see what they say when you file for a permit required for finishing the basement. (You also need an egress door or window from the basement- even without bedrooms down there).
The furring strips attach to the concrete, through the foam. If a frame wall, air seal/insulate the rim joists, sill sealer under the p.t. plate for a thermal/capillary break, no gap at insulation for convective loop to degrade the cavity insulation 20-30%; fire-stop the frame wall every 10� lineally, and ADA- airtight drywall approach to stop warm (moist) basement air from reaching the cold concrete wall to condense there.

Gary
 
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Old 04-03-11, 02:21 PM
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People get all hung up with the so called "frost depth" as governing everything. It is an arbitrary designated number designed be deeper than the frost would ever penetrate forever and is for an exposed area.

Your climate is similar to mine and not as cold as where I worked for few years. In your area, the soil temperature at 4' - 6' would normally be 50-55F minimum. If the area is protected (overhangs, or snow cover) this can cause the temperature to be much higher. I have seen 6" frost depth after 3 months of 0F or colder (up to -50F a few times).

The frost depth is frequently twisted and abused because there is really very little technical support in the code committees I have been on, but it is convenient number if used for designing stand alone structures or structures like decks that are attached to house since it takes no real technical ability to make an administrative decision. I always use the code frost depth for structural purposes, but draw the line on using it for other purposes.

The frost depth also has little to do with the designing of heating systems, since they are based on short term temperatures and not averages and then only for air temperatures because air varies widely and has no thermal or mass stability.

The poor little R-value is based on the temperature difference between two surfaces in a SHORT TERM, LABORATORY TEST and does not really relate directly to the heat R-value of a wall. A perfect example is the R19 on a roll of batt insulation. That number is used for identification of the material itself. Unfortunately, it is misused because it can be administratively used as the measure of the wall properties. R-19 insulation may give a R-11 value in some cases, even under ideal conditions, but it is routinely accepted as code complying.

I don't think you have any thermal problem with your XPS insulation. I would be more concerned with the stair width, especially if the basement will be used with bedrooms or is a living space. Even the stupid code officials will recognize averages in the application of a code requirement for a space. I would suggest you take a sketch of the 2" proposed thickness along with the photo to meet face-to-face for a suggestion. If that does not fly, propose cutting the insulation to 1" since the end result would be minimally different and still supposedly save energy (good like motherhood and apple pie)' I would also mentioned to the permitted that yo intend to make sure the new handrail is mounted securely to appropriately spaced support BEFORE he brings it up.

The Wisconsin codes and enforcement have become more realistic from what they were 30 years ago when they accepted insulation values with incorrect and minimal support that were up the 200% different from other states, but there are still some little quirks.

Dick
 
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Old 04-04-11, 09:45 AM
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Thank you all for your thorough replies. I really do appreciate all the info you've given me. I'm trying to process it all, lol. I am very concerned about the fact that the stairs are supposed to be 3' wide, that is something I have been worried about for some time! Thank you for suggesting that we meet face to face with our plans and see what they say. We will definitely do that. The railing will be replaced, for sure. For the past 2 yrs, I have been terrified that one of our (5) kids were going to fall because of the rail that's there now. Someone mentioned egress windows, so I thought I'd mention that there will be egress windows because there will be bedrooms, but that is a whole 'nother thread!
Thanks again!
 
  #7  
Old 04-11-11, 04:39 PM
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Good day!

I'm in the exact same situation. Hopefully not hijacking, but asking more questions that might be pertinent to the OP, and certainly are to me

My stairs are 38", so I should be able to use 1/2" foam board, 1" furring and 1/2" drywall and still maintain a 36" step. So the Drywall will sit directly on top of the stairs, meaning I (we) will have to notch it around each and every bull nose. Making that look perfect will be a challenge at best.

So how to finish? Cutting a skirt board around the bull nose would be insane, and That would technically cut into the remaining with of the stairs, potentially meaning it's not 36" wide anymore. Any ideas?
 
 

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