# Trim old drywall resting on slab?



## Klawman (Nov 10, 2009)

After demoing the old ground floor flooring I found that some of the perimeter walls had the drywall installed so that the bottom edge rests on the concrete slab. Should I trim those bottoms about 1/2" off of the slab or leave well enough alone? After 24 years I don't see much wick up damage, of which the worse is pictured in a close up. The general condition of the wall is shown in the other photo. I am covering the old edge by using a taller base board that will be installed on top of the new flooring (as opposed to the ones just removed which were on slab).

Thanks.


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## jogr (Jul 24, 2007)

After 24 years of no problem the only reason I can think of to do so would be if you have absolutely nothing else to do with your time.


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## Klawman (Nov 10, 2009)

I concur with you jogr. Especially as the one worse area, which is depicted in the close up, is very near where a window flashing was discovered to be leaking and was fixed some 8 years ago. Also, for 12 of those 24 years that wall, which the wind blows rain against, when we get some in So Cal, wasn't protected by roof gutters.

And I have plenty to do to get this place fixed up. The joys of home ownership in retirement.


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## Gary in WA (Mar 11, 2009)

Entirely up to you. Best scenario is leave it alone. Worst is; The rusty fasteners tell me moisture from somewhere. Drywall code requires 1/4" gap. Possible wicking from exterior perimeter flower-bed watering- capillarity through slab edge. The newer Energy Codes require air-sealing dis-similar materials in the thermal/air barrier of your exterior wall. http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_11_sec002_par022.htm
You may be feeding conditioned air/or moisture to the attic, but your call. Or feeding warm moist exterior air to the room. Electrical boxes/recessed lights are big air leaks. http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/

Air leaks feed convective loops in your low-density (R-11) cavity FG batts, degrading the R-value. Links if needed...

Gary


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## ToolSeeker (Sep 19, 2012)

While I had it open I would fix it. As stated from the rusty fasteners, there is or has been moisture. So you get it all done and then something leaks so now you have to tear it all back out and do it over again. Or you roll the dice and get another 24 years, maybe.


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## carpenter69 (Jun 7, 2015)

Cut the sheetrock a 1/2" or so below your new baseboard height. This way you don't have to tape it and the problem is solved. You can even use green board or plywood.


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## Klawman (Nov 10, 2009)

Hi Toolseeker. In fact I decided not to just roll the dice and yesterday started trimming the wallboard about 1/4" from the slab. 

I am not clear on what you are saying, carpenter69. Is it not to simply trim the existing drywall so as to get it off the slab, but to cut below the height of the new BB and then install strips of new dw cut to bring the bottom of the wall to that height? Is the benefit that you then have a taped edge along the bottom of the wall instead of an open cut that may allow gypsum to erode over time and fall out the open edge?

I have attached new pictures to illustrate what I mean and have so far done. The first is the exterior wall which had some damage and I have now cut with an oscillating tool to just over 1/4" above the slab. The top of the new bb will be an inch above the old caulk line. I think you are saying I could cut the old dw along caulk line (almost as if it were a chalk line) and then butt in a strip of new dw with a taped edge set the proper distance above the slab.


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## Davejss (May 14, 2012)

Good exscuse to buy a new oscilating saw!


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## Klawman (Nov 10, 2009)

The oscilating saw I have, which is a Dremel, works great. The cut in the first picture is raggedy due to the condition of the dw and the wrong choice of blade. I should have used a flush cut blade. Regardless, the second picture is of a cut done with a Dremel Sawmax and it is a lot cleaner and easier. I just have to lay a board of appropriate thickness on the floor and use that for a height guide. The cut in that pic was laying the one side against the slab.


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