Walls and Ceilings - 2nd layer ceiling

This is an older, one story home with 1/2" drywall ceilings. The rooms are typically 12'x12'x7'2". The ceiling joists are full dimension 2x4s, 24" OC. The ceiling supports over 18" of batt and blown fiberglass insulation.

The house was vacant for several years. There are no signs of past leaks, but the ceilings are sagging. When I push the ceiling up and resecure it, the drywall appears to be "weak", as if it was damp (it's not). The screws want to pull through the paper. I'm a bit concerned about the structural integrity.

I want to avoid the mess of replacing 1000 sq ft of ceiling and insulation. So my first thought is to secure the sags with screws; level and support it using using 1/4" to 1/2" firring strips, 24" OC, perpendicular to the joists. Then install ceiling panels that staple to the firring. That would reduce the ceiling height by less than 1" and would be light weight. Unfortunately, the panels are over twice the cost of drywall.

A second, option is to fir it level and install a second layer of 1/2" drywall. The question is, "Will the joists support the extra weight?" Sistering the joists under the insulation isn't an option. What about firring 12" or 16" OC and using 3/8" sheetrock?

If I do add sheet rock, do I need to add beams in the attic, across the middle of the rooms? That would reduce the span to 6'. It would be easier than sistering, but it wouldn't be fun.

Any suggestions or words of wisdom... other than wearing a hard hat?

Thanks,
Barry

You should probably have an inspection by a contractor or structural engineer because a sagging or bowed ceiling indicates the ceiling material may be pulling away from its structural supports. Sagging can be caused by sagging ceiling joists and/or sagging strapping. Sometimes a sheetrock panel will remain sagged after old water damage dries out. There have been reports of adhesive failure causing sagging ceilings. If the house sat empty for several years, sagging could be due to high humidity.

Interesting links:

http://www.creativehomeowner.com/index.php?pane=project&projectid=chwal272

http://forum.doityourself.com/showthread.php?t=83326

http://www.mlive.com/homeimprovement/index.ssf?/hg/aroundhouse/stories/19990614zolton.html

TwelvePole, thank you for the articles and prompt reply. Unfortunately, the articles don't answer my question. I'm an engineer and I've designed and built a couple houses, but I don't have experience with older homes. These old homes never meet todays codes. Yet most of them do fine. So, I'm hoping for a "been-there done-that" or a, "whatever you do, don't do that" type answer. You know. Some of that good learnin'.

The ceiling joists aren't sagging, just the drywall, which has pulled away from the joists. This is a single layer ceiling with no adhesives or strapping. It was nailed directly to the joists. As you suggested, I believe the sagging was caused by high humidity. Some nails have pulled through or out. New screws tend to do the same. So, I'm not sure I can trust the strength of the drywall anymore.

Does drywall regain it's strength after drying (humidity wise), or is it permanently weakened? I suspect it can't be trusted. So, the main question becomes, "Can I, and how do I, add another ceiling layer given the structural limitations of the joists."

Thanks,
Barry

My concern would be the additional weight and installation over a surface that is not flat. Drywall manufacturers recommend that relative humidity be controlled before, during, and after installation. Hopefully, someone will come along who has experienced your situation.

Can you push the drywall back into position and screw it off? Or is it too britle and can break. Another reason for sagging could be 1/2" rock on 24" centers. If the existing drywall isn't brittle then you could go over your ceiling with another layer of 1/2" rock.

I can push the drywall back in place, but the sag has set into the sheets. It wants to pull back down. Screws tend to tear through the drywall, which appears to be somewhat weaker than normal in regards to screws. If I could use screws with 1" washers, I'd be set.

Once the drywall is pulled up, the ceiling is level. Applying firring strips over the drywall would hold it in place. As twelvepole noted, my main concern is the added weight of a 2nd layer of drywall. The joists are full dimension 2x4s, but they span 12' on 24" centers.

Adding a center beam or other support in the attic might be neccessary. I would run hangers from the rafters, but the rafters are also only 2x4s.

A stapled up panel ceiling would be lighter than drywall, but twice the cost. 3/8" drywall would be somewhat lighter and might not sag if I use narrow centers on the firring.

I need some sky hooks.

Barry

2x4 on 12 foot span will not hold any more weight. 2x4 will span 8 foot on 16 inch centers. You have the right idea to decrease the span to 6 foot but your 2x4 rafters will not support them.You cannot hang a beam from the rafters as they are designed to hold weight from the top not the bottom. You would need to have the beam rest on the walls below on both ends and then hang the ceiling joists from it. The size of the beam would depend on the length spaned by it. I believe you said the room was 12 feet wide. You would need a double 2x10 beam 90 degree to the ceilng joists. Then tie each ceiling joist to this beam with hangers. Then with the 6 foot span the ceiling will hold a new layer of drywall. Fasten the old ceiling with the special drywall ceiling washers made for just this problem. They will embed enough to not need any furring. Hang the new drywall with at least 2 inch screws.
I am no expert by any means but this is my suggestion.

Badeyeben, the way you described the beam is the way I planned to do it... if necessary. Although I know it needs done, I've been hoping for an easier solution. Maybe it's time to face reality.

There's only 3' of roof clearance over the intended beams. It would be a nightmare working in the attic. Instead, I'd remove a narrow strip of drywall and install the joist hangers from below. Hopefully, I could maneuver the beams through a gable vent... or else it's sawzall time.

I'm leaning toward firring (for drywall support) and stapling up textured ceiling panels. That would keep it light. The material cost is double that of drywall, but the labor is halved. So it's probably a wash.

Thanks to everyone for their input. I'm still waiting for that cheap and easy solution though.

Barry