I am in the planning stage for my workshop. I plan a 2 foot raised foundation so I can run dust collection and electrical under the floor.
The shop will be 24 feet wide and will have a beam at the mid point making 12 foot floor joists. Will the floor be siffer with 2×8 on 16 inch center or 2×10 at 24 inch center? I plan on 1 1/8 inch T&G plywood and 3/4 inch pine finished floor.
Any thoughts appreciated.
Thanks.
Replies
The thread on Floor Vibration will answer a lot of your questions.
The father replied, "I don't know, son, I'm still paying for it."
All else being equal, the stiffness of a joist increases as the cube of the depth. The depth of a 2x10 is 1.27 times the depth of a 2x8. 1.27 cubed is 2.05. If a 2x8 has a stiffness value of 1, a 2x10 of the same length will have a stiffness value of 2.05. So a 48" wide panel of floor supported by 3 2x8s @16" o.c. will have a stiffness of 3, while a 48" panel of floor supported by 2 2x10s @24" o.c. will have a stiffness of 4.1.
Of course, the floor can flex in-between the joists, and flexing of one joist relative to another can produce some of the most annoying and troublesome bounce. For the first, of course, you need either more closely spaced joists or a stiffer sheathing/flooring material. For the second bridging (done right) will help a lot.
If ignorance is bliss why aren't more people
happy?
>> ... the floor can flex in-between the joists, ...I think Marco has that covered with the 1-1/8" subfloor, but you may be right about the bridging.
Thanks for the replys. What is the correct way to do bridging on the joists?
>> What is the correct way to do bridging on the joists?Well, the way I'd do it is to glue and screw a vertical 2x4 by 9" cleat on each side of each joist bay and then glue and screw a 9" x 14" piece of your 1-1/8" plywood to the cleats, leaving a 1/4" gap between the plywood and the vertical faces of the joists. By holding the blocking back from the joists and the subfloor, you guarantee that it will never rub - and therefore never squeak.But that would be massive overkill, and I'm sure others here will have more economical suggestions.
Edited 3/28/2006 5:51 pm by UncleDunc
Unless this 24' wide structure is 200' long, I'd go with 2x10's at 16" o.c. and get the best of both worlds. For the minor cost difference, it'll be well worth it- especially if you load a lot of equipment and material into the shop. 2x8's @ 16" can easily span 12' in a residential loading condition, but you may overstress them in a shop scenario.
Bob
2x10 at 16" center would be stiffer
how much would you save by going 24" on center?
how long are you planning on keeping this shop?
just my way of looking at this
enjoy your new shop.
Erich