# Filling gap in inside corner



## Spacemoose (Feb 9, 2014)

Im about to drywall a couple of exterior walls that Ive re insulated. Where the new drywall meets the old drywall Im going to have a gap, unless I can slide the new stuff behind the old. Can I leave the gap empty or should/can I fill it with backer rod, or drywall mud?


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## joecaption (Nov 30, 2011)

There should not be a gap if the sheetrock was installed right.
One sheet goes tight to the corner, the other butts up against it.
You did install nailers in the inside corners, right?


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## ToolSeeker (Sep 19, 2012)

Spacemoose said:


> Im about to drywall a couple of exterior walls that Ive re insulated. Where the new drywall meets the old drywall Im going to have a gap, unless I can slide the new stuff behind the old. Can I leave the gap empty or should/can I fill it with backer rod, or drywall mud?


Let me see if i've got this right the gap is going to be in the _back_ of the corner. Can you not slide the tapered edge of a sheet behind the other. This could be mudded but even with hot mud this would be a very crack prone area with the void behind it.


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## Spacemoose (Feb 9, 2014)

The tapered edge does fit in the gap so I could do the wall vertically. There is however a giant window in the center of the wall and because of the age of the house nothing really lines up as you would expect. The other tapered edge would fall just past the nearest stud (the green line). Same with the other side. There's about a 2 foot gap in between that id have to fill.

Hanging horizontally Im left with the gap in the corner where the drywall doesnt fit (between the blue wall on the left and the insulation) and a seam at the bottom corners of the window.

edit: I have 4x8 sheets of drywall, the wall is just shy of 10 feet long.


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## Jb1234 (Aug 18, 2012)

Hang horizontally, need 3 sheets, boom done. Use a scrap piece of drywall as a scribe on the old. Trace and cut it out and slide the new sheet in behind it. Corner bead, mud, sand (I'm simplifying) done. Unless I'm missing something.


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## ToolSeeker (Sep 19, 2012)

I agree on hang horizontal use a 12' sheet over the window, any joint over the window or at the end of the window will crack. Hang the sheet over the window then run a Rotozip around the inside window frame, perfect fit. Put 8' sheet under the window this will avoid what we call railroading, which is the seams stacking on top of each other.


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## Nailbags (Feb 1, 2012)

Whoa! Looking at your wall is that insulation have kraft facing on it? if it does take the plastic off! or you will have major mold problems.


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## princelake (Feb 19, 2012)

just butt the boards up and prefill any gaps with easy sand and then go over with tape mud and paper tape.


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## ToolSeeker (Sep 19, 2012)

Nailbags said:


> Whoa! Looking at your wall is that insulation have kraft facing on it? if it does take the plastic off! or you will have major mold problems.


Good catch. That is why pics are important.


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## Spacemoose (Feb 9, 2014)

Nailbags said:


> Whoa! Looking at your wall is that insulation have kraft facing on it? if it does take the plastic off! or you will have major mold problems.


Its Roxul insulation (rock wool), its brown so it only looks like it has a paper facing (i assume that what you mean by kraft). The poly is required by code (in Canada) for the warm side of insulation of exterior walls. 

The bottom of the window is almost exactly 4 feet off the ground (4' 2") so even using 10' or 12' sheets of drywall will leave a seam at the corners. I also doubt I could get a 12' sheet in the room, 8' sheets were tricky enough to maneuver through the hallway. I think my best/easiest bet at the moment is to use 4 sheets that are ~ 5' long (which gives 2 butt joints, one above the window one below at about the center). As for getting drywall behind the old stuff I can try and shave 1/8 off the edge.

the picture is not exactly to scale.


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## acldesign (Feb 24, 2014)

Paper backing + vapour barrier. Terrible idea.

Use a olfa knife and scribe the edge of the drywall on an angle so it slides behind the other sheet.


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## Spacemoose (Feb 9, 2014)

Close up of insulation (minus poly) and corner shot to show where the drywall would be if laid horizontally. The ~ half way point (5' from either wall) is the stud the electrical box attached to.


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## Nailbags (Feb 1, 2012)

yah its good rock wool is the da bomb! your doing it right.


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