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RICKM15752 06-30-2011 04:02 PM

Shimming for ceiling drywall..Where to start???
Hi everyone,
I'm replacing the drywall on my family room ceiling. The room is 12' 6" by 18'. My joists are 2 x 10 on 16" centers. The joists run the length of the 12' 6".

I checked the joists with a string and found various degrees of problems with it in terms of being flat. I'm not so concerned with it being level. I just want to get it reasonably flat so the new drywall won't be noticeably wavy.

I have the cardboard shims from Lowes as well as some 1/4" redwood lath.
I have a 6' level, power planer and laser levels.

My question is, where is the best place to start in terms of shimming or shaving? Do you start at the top plate in a corner and make that your reference point?

I don't want to use metal studs or put anything other than shims on the framework. I want to keep the ceiling height as close to it's 8' height.

Thanks for you help.

Bud Cline 06-30-2011 05:18 PM


My question is, where is the best place to start...
Start by calling your local Real Estate person to see their current listings.:)

Okay okay...not so funny.

I personally think you are asking for trouble. What you propose isn't that easy to do with a ceiling. I honestly think it would be easier (and do-able) to sister the rafters with new stock. Without knowing the current degree of imperfection you have there is no way to advise you sensibly.:)

RICKM15752 06-30-2011 06:04 PM

Hi Bud,
My initial post probably makes me sound like a novice in construction, which is not the case. I'm a very capable diy. My home project is quite extensive and being done under a building permit. So far, everything I've done has passed the building inpsector's scrutiny.

I'm quite capable of furring or planing the framework to make it flat for drywall. I've done this with vertical walls and the drywall is very flat when I put a level to the plane.

I can apply the same technique that I used on the walls to the ceiling. I was hoping there was someone who has done a lot of this who could share some 'tricks of the trade.'


Bud Cline 06-30-2011 06:28 PM

Okay then go for it.

Use a string line to tell you where to shim. Install the shims. Install the drywall. You are right nothing to it on a ceiling.:)

1910NE 06-30-2011 09:06 PM

Where is the video with the British guys using the metal channels to level a ceiling? Otherwise, lots of work..

chrisBC 06-30-2011 10:19 PM

I would run stringlines over the whole ceiling, lengthways and widthways, and figure out your high/low spots as well as level. You may have to cut a tapered shim, and then shim off that to get a level plane. When I say shim i mean cut an 8' shim or whatever the length you need out of a 2x4, then glue/screw to the joist. If you want to bother with the small shims then just shim it as you board, but don't expect the same results. Last ceiling I did though the owner didn't want to spend all that much time (money) on making it perfect, so we did this as we boarded and once was mudded it looked fine. No texture.

as suggested by bud another way to get the exact same results would be to sister 2x4's on, just in the areas which need to be added too, faster than cutting shims. Maybe a combination. Important though to know what is going on over the whole thing, not just 4' at a time, or you may end up doing a lot more work than you need to.

shouldn't be that hard, or take all that long probably, if you take your time and determine what's going on, good luck.

Bud Cline 06-30-2011 10:32 PM

A human nature aspect to consider is that: People don't look up.:no::yes:

chrisBC 06-30-2011 10:36 PM


Originally Posted by Bud Cline (Post 677634)
A human nature aspect to consider is that: People don't look up.:no::yes:

very true, I wouldn't get too picky over it, mud and paint will work wonders.

If it's an easy fix for a pretty bad situation then great, but I wouldn't spend hours making sure everything is within a sixteenth.

dsconstructs 06-30-2011 10:39 PM


Originally Posted by Bud Cline (Post 677450)
What you propose isn't that easy to do with a ceiling. I honestly think it would be easier (and do-able) to sister the rafters with new stock.

That is the answer.
And in case you don't know what he means by "sister" it isn't going to change your ceiling height. In this case, it's running straight wood alongside bowed wood so that the straight edge of the new wood runs just past the original wood for a nice straight ceiling. Your ceiling height doesn't change. It's not getting attached to the edge of your ceiling joists.
Take you about an hour, use screws.....and I guarantee you a flatter ceiling than you'll get messing with shims all day and then some.

tcleve4911 07-01-2011 06:55 AM

My first question would be bad is it?
If the joists are within a 1/4" on plane, you will never see any "wave".

1/2" drywall @ 16"o.c. with flat white ceiling paint will hide a lot of imperfections.

RICKM15752 07-01-2011 03:34 PM

I have 4 joists that are about a 1/4" off plane and I would need to use 4 layers of the cardboard shims along most of the length to bring it back on plane. I've used this material before for walls and then only two or three layers. I've not used this stuff on ceilings and never 4 layers.

I'm using 1/2" ceiling board and 1 5/8" coarse thread drywall screws. I usually shoot 1 1/4" screws. But, because of the shimming and the ceiling board, I wanted a longer screw to ensure holding strength. That is about the worst of it. Eight of the other joists needed some planing to bring them in line.

I know about sistering and had to do some on the verticals walls.

I could sister the 4 joists.

Would 2 x 4 be sufficient? Or would I need 2 x 6? The joists are 2x10.

These would span 12' 6". Any requirement to support the ends on the plates?

Screws? Spax #10x 3" O.K? How many per board?

chrisBC 07-01-2011 03:48 PM

if you know it's a quarter inch and only four joists, personally i'd just rip a 2x4 or two down to quarter inch shims (by eight or ten feet, whatever), glue and screw onto bottom of joists, that way you can keep your O.C. and won't have to buy as much material. Wouldn't take very long, skillsaw or tablesaw. don't bother with your cardboard shims here. Use a bit longer drywall screws for this area if you want.

again I wouldn't get too picky about the rest of it, the board will cover a lot.

RICKM15752 07-01-2011 04:21 PM

Thank ChrisBC
I agree, I will just shim these and move on.

Bud Cline 07-01-2011 04:21 PM

The problem I see with the shims is gluing the drywall to the joists. Don't you normally glue the drywall to the joists? Here they do. On a ceiling I would think it would be mandatory.

And remember...people don't look up.:) That thing isn't far enough out of bounds to worry about.:) I'll bet they are all like that.:)

chrisBC 07-01-2011 04:26 PM

I think this is where these places are interesting- In the area I work in, I can't remember once seeing drywalled getting glued to walls or ceillings, be it a residential reno, new construction, etc. As an employee of a large reputable GC doing work, and as a freelance guy, never glued drywall in my life, and can't remember ever seeing it being done.

Besides how would that work on exterior walls with VB?

I'm just trying to visualize the situation and give tips on what i've done in the past that have worked well. throw some shims up, tack them in place, the drywall screws will go through them and into the structural members. Just my two cents anyways.

More often than not here the drywall is screwed to rez channel anyways.

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