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Barrel 12-31-2012 01:12 PM

Framing walls under a manufactured house
Hello, I am about to start framing my interior walls in my basement. I have a manufactured house and do not have typical floor joists. They are steel and are anywhere from 6' to 8' apart. I'm not sure how to attach my walls properly to them or if I have to build some kind of a sub floor system inside of the beams. Any help to get me started would be greatly appreciated.

Beepster 12-31-2012 01:43 PM

Really, there are no previous "barrel"s here? You are the first?

I did this on my mom's basement. I just screwed the top plate to these 'joists' using 2" self tapping steel screws. Then where the two top plates met up I used a 2 foot 2x4 chunk to tie them together above.

Tapcon the pressure treated bottom plate.

XPS on the wall's? Where are you located? There is a shootload of posts on insulating basement in the Insulation section.

Barrel 12-31-2012 02:43 PM

Lol, I know, barrel is usually taken. Thanks for info, I wasn't sure if that would work or not. I live in northern mn. Have been debating on xps or eps for some time. Have done lots of research and just can't decide yet. Currently I'm leaning towards eps.

Beepster 12-31-2012 02:57 PM

Northen MN? My mom's place is by Waubun, 30 miles north of Detroit Lakes.

Here in the Cities I did 1" XPS with R13 un faced fb bat insulation. I monitored the humidity level during last summer and was OK.

Barrel 01-01-2013 12:22 PM

What did you do for moms floor? That is my only other area of question. My basement is basically dry. My walls are good but in recent years I've noticed the floor being slightly damp from time to time. Thanks again for the help.
By the way I'm bout 30 minutes sw of millelacs. Outside a little town called Hillman

joecaption 01-01-2013 01:45 PM

Really need to address the reasons that floor is getting moist before doing anything. No form of paint of flooring is going to work out with a moist floor.

Something like this might work for attaching the walls.

Gary in WA 01-02-2013 10:43 PM

As the foamboard will be next to a wet concrete wall, and wet most of the year, it will lose R-value, fig.7;

An easier chart;

Using Dec. Jan., Feb. lows for your average 9*; I'd go with XPS, R-15 (2-1/2") will keep you safe from condensation (above grade down to frost line) at and above 32%RH in basement at 70*, which will keep the frame wall cavity insulation dry;

OR, R-10 (2") at 27%RH, or R-5 (1") at 17%RH. Or R-15 ESP at 4" though it lets a lot more moisture through the wall, go to 6" for safe moisture control; pp.33-34;


Barrel 01-03-2013 12:56 PM

Thanks Gary. I've came across a lot of your posts while researching my basement project: always good and informative! My last question which I've found plenty of threads about but can't seem to find the best answer is should I do my subfloor first and then frame walls on top of it or do my walls first and then subfloor up to them. I think I will go with the 2" xps for both walls and floor(I have plenty of head room). Just not 100% sure on the best order to do it in. Thanks again for everyone's help.

Gary in WA 01-04-2013 03:20 PM

I would add a poly sill-sealer under the p.t. first (to make that line air-tight, mainly, also serves as a thermal barrier and capillary break);

The s.s. would conform more easily to slab irregularities, I think, and no need for a sealant/caulk there- then, as opposed to setting the plate on a rigid foam board. Then butt the slab f.b. to the wall, caulking the edge (and that perimeter edge under the f.b.) near the wall to stop moisture/air from feeding that joint. So any air movement at the f.b./slab would be stopped 1st at the edge of flooring, 2nd at the sill- sealer, 3rd at the canned foam under the concrete wall's foam board and those vertical joints mastic/caulk/taped.


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