Attic Conversion floor joist span

dodzy

Eventually planing to tackle attic conversion over coming quarter. floor space will be approx 16 x 16 ft once complete. Just wondering will i need a 3rd RSJ in the center aso opposed to just using 2 RSJs - thinking that a 16 ft span potentially excessive with a possibility of flexing under foot traffic ? or would 7x2" at approx 2ft centers be sufficient spanning 16ft approx.

endasmail

put in 9x2 and spread them at 400 mm centers
dont no standard requirements off the top of my head
you could check them up though

gsxr1

I would put them in at 300 for 16'. 9x2

dodzy

Thanks guys, I was hoping that 7 x 2 would be sufficient as the plan was to fit each end into the T section of each RSJ. These will be 9" in height - the 7x2s would fit in nicely. Might just go with above reccomendation and use joist hangers.

harry21

Go with the 9x2 at 400 centers. then notch them to fit into the RSJ (I beam) at the end. You can afford to lose the height and the ends, its in the middle you need it.

The 7x2 notch will be fine for shear and 9x2 in the middle will provide enough bending strenght.

Happy days:D

sky6

Yes Definitely use 9 by 2. You can shape the ends to profile the RSJ and any little height above the RSJ can be made up with a slip or used to run cables along the RSJ.

gsxr1

http://www.home-extension.co.uk/tech2.html

useful link

dodzy

gsxr1 wrote: »

http://www.home-extension.co.uk/tech2.html

useful link

Very handy guide gsxr, ta