Is my garage roof beams strong enough for plasterboard

[ashleytowers]

I'd like to ideally plasterboard out my roof (and some other bits) of my garage to make it more pretty and make it a bit more multipurpose (thinking of turning it into a games room). However I dont know if the timber beams are going to be strong enough? There is 5 of them with a length of roughly 5 meters they are 57cm gap between each. the beams are 70mm x 35mm (give or take a mm or two). And currently its been turned into storage with chipboard being put down. Would it be strong enough to plasterboard it keeping in mind i'd probabily keep it as storage.

Some pics of the roof i hope you can see them (not tried flickr before.)
http://www.flickr.com/photos/23459032@N04/show/

I suppose its the length of these beams (5 meters ish) with no beam in the middle that worries me.

 

[Deluks]

I doubt it over 5 metres, loft boarding or plasterboard but not both.
It appears to be a front to back roof, the trusses are spanning the length and not the width. If you can lose some head height and fit some other lengths widthways, underneath the bottom chords, and fixed to the downstairs side walls, then you'll be in business.

See if you can find any manufacturers markings on the trusses themselves and contact them for advice.

 

[ashleytowers]

Thats what I was thinking with the length, as for doing them widthways would I just put a batten (obviously a big one) to the wall and have the wood rest on that (I'd have to hide the rest then) or would i really need to build some walling. Yeah if they had done it widthways it would have been ok (doh!). the height is 245cm to the battens so I can afford to lose some height. would the same 70mm x 35mm do the job for the widths or would it be better to go stronger?