what size timbers to stiffen ceiling for loft play room?

[Glenbirnie]

I have a loft in an old house im looking to floor and make semi inhabitable for kids to layout train sets, scalectrix etc

The trusses are simply triangles, ie one horizontal and two angles, they are not like attic trusses or fink, no hanging posts etc.

The timbers are 5" x 2" and some that arent over the two bedrooms and bathroom underneath flex a bit when I stand on them (Im 18 stone, big boned not a fatty!)

The height in the middle up there is only about 7 foot and its a steep roof angle so I have no intentions of having wild partys up there. Just a space for the kids and a couple of their mates.

My joiner has suggested laying timber perpendicular and fixing them with inverted joist hangers to the existing horizontals. This sounds like a plan but the thicker the timbers the more weight and less room height.

I was considering using 3" timbers across the current 5". Do you think this will provide enough extra stiffness?

I will also them be floornig it with lightweight pine T&G, maybe 16mm.

Thanks

 

[jiminyrock]

Others may well be able to advise you better than me, but if it was me in your position I'd get an engineer. Our roof use the same sized joists and rafters at centres that varied from between 45 and 60cm. We had no collar, but we did have a hanger. We wanted to do similar to you, but with the option of having the ability to convert it formally in the future. The engineer advised with that size of joists we could make the hangers vertical (they were angled in) giving us more floor space and we added a collar quite high up, but we didn't need to increase the size of our joists. Obviously it will depend on your roof and how long the joists span, but we found it worthwhile and I use the loft pretty now that I've floored it secure in the knowledge that it is totally safe, and I can convert it in the future if I need to.

PS why the username daddad, I only ask because I knew someone else who used the same username who did so because he played guitar tuned daddad... ...an odd but surprisingly effective tuning....

 

[stuartturbo]

what is the span between end points off beams?
As my loft conversion has a span of 3.1ish mtrs and uses 6x2" on 400mm centre. on current wall plate (ceiling joist was 4" new is 6" on a 1" packer so 3" higher.Your recommended way would be 6" higher, and when limited it all adds up)
if you have 5x2 it may be possible to fix a 2x2 on top glued and screwed.
once everything ties together with noggins and flooring, the beam would flex less.

 

[Glenbirnie]

Span between joist ends is 4 metres.




PS why the username daddad.

Thats what my boys call me and when your asked for passwords, names etc on computers i never have a clue what to use!

 

[stuartturbo]

span tables suggest a fair list of poss sizes
195*47
170*75
being the shortest