Exposing standard roof trusses

[ronafios]

I have a living area of around 40m2 that is a bit dark, and I was looking to install a couple of Velux sky windows. The installer essentially mounts the window between two trusses and builds a gyprock box down to the roof line. But thinking about it, I wondered why I shouldn't just drop the whole ceiling and expose one half of the trusses and gyprock to the roof (as per picture below) adding the sky windows. Then paint the whole lot (including the trusses) in ceiling white. This won't affect the structural integrity of the roof, and for an informal living area I think it would look fine. There is only one single lighting electrical cable going to the centre of the room, which would be easy to relocate - no other services in that part of the roof.



Has anyone had any experience doing something similar? In particular I'm interested in the fixing of the plaster to the new roofline. Battens on the underside of the trusses to attach the gyprock to, and insulation between the gyprock and tiled roof?

Any insight or experience is valued.

[billbeee]

It is done quite often, but remember that the bottom chords of the trusses are held in position by the ceiling battens.
Remove them and then you must replace their stiffening with something equal.
Most cases I've done with exposed trusses (usually in garages) we fixed something like 75 x 50 on the top of the bottom chord with triple grips at say 1/3 or 1/4 span positions.
It will be a bit fiddly fitting a ceiling up there, especially if you have wind braces in the way, but it can be done.

Right here is where I should say something about building regs etc. but you guys down south seem to have weird ways of doing things so I don't bother anymore.

Cheers
Bill

[pawnhead]

It is done quite often, but remember that the bottom chords of the trusses are held in position by the ceiling battens.
Remove them and then you must replace their stiffening with something equal.

I did one ages ago, and the engineer wanted a cable drilled through the bottom chords with U bolts either side to restrain them.

[toecutter]

It is done quite often, but remember that the bottom chords of the trusses are held in position by the ceiling battens.
Remove them and then you must replace their stiffening with something equal.
Most cases I've done with exposed trusses (usually in garages) we fixed something like 75 x 50 on the top of the bottom chord with triple grips at say 1/3 or 1/4 span positions.
It will be a bit fiddly fitting a ceiling up there, especially if you have wind braces in the way, but it can be done.

Right here is where I should say something about building regs etc. but you guys down south seem to have weird ways of doing things so I don't bother anymore.

Cheers
Bill

Iam a truss detailer and you should not remove battens if they are there as they form the cieling diapham which is part of the truss systems bracing component.
Every roof is designed for a specific/individual application.

[silentC]

Interesting. The people who supplied my trusses never even asked if there were going to be ceiling battens or not. It was optional whether we used them or not, and in the end, we decided to go with furring channel, just because we had a few direction changes and some slightly wobbly bottom chords.

Now don't tell me that my 12mm gyprock ceilings are part of the truss system's bracing component...

[toecutter]

It will depend on what the detailer speicfied but usually the properties of the ceiling are a option the detailer includes in the truss design.

[DvdHntr]

I did one ages ago, and the engineer wanted a cable drilled through the bottom chords with U bolts either side to restrain them.

Pryda Engineer?

Iam a truss detailer and you should not remove battens if they are there as they form the cieling diapham which is part of the truss systems bracing component.
Every roof is designed for a specific/individual application.

Correct. The trusses are laterally braced by either battens or direct fixed ceilings. Furring channels are a mystery to the Frame and Truss Industry. But you will find that many people will say that over battens or hangers should be used when they are used.

On the original issue, there are a few ways to achieve the sky light.

1. Cables as the other engineer stated
2. Replacing the ceiling diaphragm with battens
3. Adding timber to the side of the existing truss bottom chords
4. Covering both sides of the trusses with plywood and painting.

I'd advise the last option as is will look the best and be more structurally sound. The best solution is to contact one of the three nail plate suppliers to ask for a design. That will probably cost you $150-$200 but they can certify it is engineers.

Or if you have the details and I feel generous I can work out some sizes and provide an installation guide, as long as you don't want it certified, to help you.

[pawnhead]

Pryda Engineer?

I've got no idea. It was a long time ago when I was just a green carpenter's apprentice, following the builders orders by installing the cables and U bolts, but I can't imagine that the site engineer would want to become involved in truss design specifications. I'd say that it was sorted out between the architect and the truss supplier, leading down to the monkey on a ladder, with a spanner and the U bolts in hand.
Only a bit less than half of each truss was exposed. There was a bulkhead from the roof line down to the ceiling, which covered the other bulk-half of the trusses.

[trivia]
It was a beach-side café at Palm Beach called the "Beachcomber" which has since been torn down and replaced with another enterprise that can extract even more $ from the public. [/trivia]

[DvdHntr]

Yeah, just curious and offering a little info that I know that Pryda offer that system. Personally, I don't like the cables but if installed correctly they will work.