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Hi, I'm Dave Osborne. With over 50 years experience as a journeyman carpenter, foreman and contractor in heavy construction I enjoyed working with apprentices and sharing the tricks of the trade that others shared with me. Now I get emails from Members all over the world and we include many of my answers in our Free Monthly Newsletters. Some of my answers include drawings and instructions specific to a project, but may also answer your questions. I use correct construction terminology, so you can confidently inform your building supply dealers or contractors exactly what you need.

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Tables 2: Span Tables for Joists

These joist span tables are taken from the National Building Code of Canada, 1998 BC Edition (still current) and are for reference only. The final authority in building codes, including joist spans, lies with the building inspector in your local area. To improve the span of floor joists it is recommended to use 5/8" tongue and groove standard sheathing grade sub-floor, glued and screwed, with bridging between the joists and strapping below the joists. If the ceiling is finished below the floor, drywall is considered strapping.

Maximum Spans for Floor Joists in Living Quarters

Span in feet-inches using #2 and better

SpeciesDimensionSpacing of Joists with Strapping and Bridging
12"16"24"
Hemlock
Fir
2x46'-106'-25'-5
2x610'-9 9'-9 8'-7
2x813'-912'-911'-3
2x1015'-1014'-913'-9
2x1217'-916'-715'-5
Spruce
Pine
Fir
2x4 6'-6 5'-11 5'-2
2x610'-3 9'-4 8'-1
2x813'-112'-210'-8
2x1015'-114'-113'-1
2x1216'-1115'-914'-8



Maximum Spans for Ceiling Joists
Attics not Accessible by a Stairway

Span in feet-inches using #2 and better

SpeciesDimensionSpacing of Joists with Strapping and Bridging
12"16"24"
Hemlock
Fir
2x410'-89'-98'-6
2x616'-115'-413'-4
2x822'-220'-117'-7
2x1028'-325'-822'-5
2x1234'-531'-327'-4
Spruce
Pine
Fir
2x410'-29'-38'-1
2x616'-114'-712'-9
2x821'-119'-216'-9
2x1026'-1124'-621'-4
2x1232'-929'-1026'-0


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Dave

(Ask Dave) (About Dave)



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