new garage roof trusses

[ferguson1947]

hi all building a new garage and want to use rafters to give maximum headroom the width of the rafter would be 16ft
can I use 100mm x 50mm steel box section with timber noggins the roofing would be box profile sheets
it is of lean to construction bolted to an existing wall and a new outer block wall
what spacings would be recommended the length is 17ft

 

[freddiemercurystwin]

Why on earth would you want to use steel rafters?

 

[ferguson1947]

in steel u can use shallower rafters in timber I think I would need rafter 2 to 2.5 times thicker limiting headroom I only have 2050mm to top of roofing sheet at the eaves so with rafters and sheets in steel will have around 6ft in timber around 5 ft

 

[freddiemercurystwin]

They would be shallower but timber is far more forgiving/easier.

 

[ferguson1947]

need someone to confirm that 100 x 50 steel is ok as headroom height is so important and or what size timber could be used in its place

 

[ferguson1947]

each roofing sheet would weigh 35kg per metre width

 

[^woody^]

Good luck if you get someone to calculate that for free on a forum, and accept the liability

 

[ferguson1947]

ok no one like steel what size timbers do I need 6x2 7x2 8x2 etc they can be braced top and bottom at 45 degrees to the walls if required

 

[tony1851]

If using timber on a 16ft span, you would be looking at 8x2s.
Even 100x50 box section might bend a bit.

 

[ferguson1947]

Thanks tony would steel chanel be better or I could run a steel beam the length of the garage then the rafters could be timber and maybe 4x2 or 3x2 check the pics the steel would rest on the existing rear porch and the lintel above the new garage //media.diynot.com/202000_201366_65583_39838395_thumb.jpg //media.diynot.com/202000_201366_65584_30287729_thumb.jpg