How to install shower liner on bowed drywall?

[mist42nz]

I've watched several DIY shower unit installs.  I'm getting a plumber to do most of the work since it's the first time working with such units, and there was existing bath/shower combo pipe work to be removed or rerouted.

But I've got the drywall sheets up (aqua"gib"-like product). And despite many many measurements and careful sanding, it turns out the old timber frame is concave-bowed in the middle. Stud is 2400 (ie 2410mm ceiling). top and bottom line up, but there's a 5mm gap in the corner.  My level is about 750mm long, and in every plane and along every stud and dwang/nog, it tested as true and flat before I put the drywall on.  Vertical, horizontal, diagonal. Only a few peeks of light at the joint gaps.  But put the drywall sheet on - lo and behold, 5mm bow in the center of the mixer/shower head sheet.  I've haven't got a third sheet into the tiny room to check the second wall.

Is it savalageable?  What can I do?  it's a two sided liner with moulding to go in.  I REALLY don't have cash to pay a builder or anyone else (a $10,000+ bill elsewhere to pay).
 How can I not get such bow in the future - I checked this _dozens_ of times, paranoid level of checking.

And what is the fix?  It's a multistory house, with handiplank wall, and I'm not going to replace the whole stud (@ good chunk of wall).

[Jewelleryrescue]

Hay @mist42nz 

Your welcome re drawing it also help me organise my  thoughts about topic.

I am betting myself and dozens of  others would have fixed the panel the same way as you did with the tools you used and  got that same  bow.    If not that then we made  a 1000 other mistakes  else where that we all learnt off them. The richest  self made people in the world made many  mistakes before they succeeded.  The secret here is  just to take it on board like you have,  fix the mistake as you personally want too and grow with more skills like you are doing.

So that means you are doing a perfect job at least you want to improve the result where so many other trade people just  leave it  hidden. So stand tall.   I/we only  offer solutions  to aid you best we can  we feel your pain at worksite

Your right about  builders line and slightest touch will mess it up I have slight a dip in my recent 12meter front wall 2mm just because a grass blade was on it.  Thats what those ultra blue rectangles in diagram does it stands string off the wall clear of wall bumps they  can be 5mm or 40mm to ensure no touching any thing.

Question what  glue  do you use to  glue/fix shower fiberglass to wall? if for example you use silicone it will span a 5mm gap for sure.   That  corner panel  glued to wall will never self pop off .  Previously  I have had to take  large stone panels 12mm thick of drywalls and it was extremly hard to get it to come away with only silicone holding them.  ( Dont  use  liquid nails here as if it  gets damp it fails as a glue.)  I think silicone will hold a rave party in the  shower cubical and not fail.

RE using short pieces well the truth is  small  sections will hold the wall in place perfectly flat until wall glue sets think about tiles we use skinny little spacers  until glue dries and we pull them out.  In  dry wall we put  glue top to bottom of stud that glue will squish out at packed pieces but squish a little less at 5mm gaps (add a little extra glue here)  but contact is made from top to  bottom so once glue dries your stud is is fixed 95% with new sheet and wall and as solid as a fully contact stud with no bows.  There is a limit to how far that glue will span so in that  case rip some timber.

You fixing your saw  or replacing?  Some ozito gear is  ok and not to pricy you probably  can buy 3 saws for one.. But a good  brand saw dose everything I am using mine now  in cross cut mode (Triton)to dry cut marble with a diamond  blade its coming up aces. 

[EricL]

Hello @mist42nz

It's great that you've received excellent advice from @Jewelleryrescue. Just to add to the ideas suggested, have you considered using Porta 40 x 5mm 2.4m Moulding Pine Round Edging Clear in combination with an Ozito 82mm 750W Planer? I know it's more fiddly but this is what I use to do when kitchen walls were all out of alignment. I suppose when it comes down to the 1mm gaps you can use more adhesive as @Jewelleryrescue mentioned.

This would also be a good time to think about getting an Ozito 8m Cross Line Laser Level Plus Tripod. This will give you a true straight line and you would see how far you would need to plane the timber packer to get to the correct level. Any part that's peeking out will be hit with the laser and you would see it as a red sliver.

If you need further assistance, please let us know.

Eric

[Jewelleryrescue]

@mist42nz   @EricL 

That ozito  cross line  laser  cheap as  chips I sure  wish I had one for a tonne finished projects. sigh 

I made  do with 20 meters clear tube with water level and a  coke bottle reservoir  and  i was never out more than 1mm and thats around the  corner  and up the garden  path on brick work  as  lasers then where in the  thousands of  dollars.