Drop / Floating / Fake Feature Ceiling Planning

[ffelt]

Hi all,
So far I've completed many jobs with the help of this forum so thanks for the help so far

In my kitchen I'm planning a fake "feature" ceiling to accommodate a recessed extraction unit - something like:
http://www.houzz.com/photos/70475/Modern-and-Colour-make-a-statement--modern-kitchen-toronto. I don't know the correct term so I've been unable to find information on how they should be built.

The drop needs to be about 180mm so I was planning to install 47x175mm roofing joists screwed perpendicular to the joists of the real ceiling at a centre spacing of 400mm. Around the edge I would then use the same 47x175mm joists turned on their side to create a lip. I would then attach 12.5mm plasterboard (probably 900mm wide for ease) across it and around the lip to hide the joists.

The result would look like:

Untitled

• ffelt
• 6 Jun 2012
• 1

Untitled

• ffelt
• 6 Jun 2012
• 1

Untitled

• ffelt
• 6 Jun 2012
• 1

Wish List:

• 47 x 175mm roofing joists

• 12.5 x 900 x 1800 mm plasterboard

• 8 x 200mm Heco Topix Csk Woodscrews (http://www.screwfix.com/p/heco-topix-csk-woodscrews-8-x-200mm-pack-of-10/48527) or similar

I have plenty of concerns however. Can anyone help me with the following:

• Is this the best way to achieve this?

• What considerations do I need to give for the added weight? The ceiling already comprises of an old lath and plaster layer and a new plasterboard layer. The room above has a bath in it. The new "feature ceiling will be about 2/3 of the real ceiling

• Do I need to inform Building Regs?

• What length/size screws should I be using? As long as possible?

Many thanks in advance.

Al

 

[maltaron]

Without thinking too much at present about alternatives, i would comment that your ideas are vastly too heavy, The structure could be made in much lighter material, possibly plywood. How heavy are your extracion units?

 

[noseall]

The timber section size is mahoosive and needs cutting back to say 100mm x 50mm.

Consider using 450mm centres for 1800mm plasterboards.

Regards screw sizes; You need say 40-50mm into recipient masonry and say 30-40mm into recipient timber.

 

[ffelt]

maltaron, thanks for your suggestion. I guess if I use plywood I would be able to make a lighter-weight carcass to panel onto instead.
The extraction units are simply baffle boxes with grease filters (http://www.justfans.co.uk/egg-crate-grille-with-removable-mesh-grease-filter-p-951.html) so they're not going to be really heavy at all. I then intend to use two wall mounted fans (http://www.justfans.co.uk/swf-sidewall-fan-p-823.html) on the outside of the house to pull the air through which will hopefully keep the noise down. The ducting will pass into the void above between the ceiling and floorboards.

noseall, thanks for the information about the screw sizes. Using 450mm spacing would be ideal. I chose 175mm as it would give me the depth. Is there a lighter weight alternative to roofing joists?

Thanks again, Al