Calculating lbs/sq ft.

[radioman]

you have gotten my curiosity. Is there a reason you need to use lumber for a floor for your tractor ?

 

[bncsauve]

Just estimating: I would say my tractor, roughly #3500 lbs without bucket or backhoe or bh subframe and estimated 200 sq in contact patch for each back tire and 50 sq in for each front tire seems to be 1750 lbs on the back divided by 400 = 4.4 lbs per sq in in the back x 144 = 634 lbs per sq ft in the back and 1750 divided by 100 = 17.5 lbs per sq in in the front x 144 =2520 lbs per square foot in the front. Pretty large point load. Your floor decking will need to accomodate the point load. Area loading is roughly 5 feet x 6 feet = 30 sq ft, divided into 3500 lbs = 117 lbs per sq ft area load. Your floor joist will need to accomodat that. Without looking up load ratings, I would guess you would need at least 2x10s 12 inches on center with 3 layers of 3/4 inch plywood, with spans between supports no longer than 6 ft for the 2x10s.

 

[texbaylea]

Do not use milled limber!! The strength is too variable. Look at engineered floor joists where you can get span/load tables. Also with 1" or better tongue and groove plywood screwed and glued to the joists, with glued joints.

When I built a second floor in part of our utility building I used 14" I-joists, 24' O.C. with 3/4" T&G screwed and glued. The span is 20'. No tractor but a lot of heavy household items in storage. When you walk on it it feels like a poured slab. I admit I found the I-joists at a bargain (surplus)

Vernon

 

[CrazyQ]

Just estimating: I would say my tractor, roughly #3500 lbs without bucket or backhoe or bh subframe and estimated 200 sq in contact patch for each back tire and 50 sq in for each front tire seems to be 1750 lbs on the back divided by 400 = 4.4 lbs per sq in in the back x 144 = 634 lbs per sq ft in the back and 1750 divided by 100 = 17.5 lbs per sq in in the front x 144 =2520 lbs per square foot in the front. Pretty large point load. Your floor decking will need to accomodate the point load. Area loading is roughly 5 feet x 6 feet = 30 sq ft, divided into 3500 lbs = 117 lbs per sq ft area load. Your floor joist will need to accomodat that. Without looking up load ratings, I would guess you would need at least 2x10s 12 inches on center with 3 layers of 3/4 inch plywood, with spans between supports no longer than 6 ft for the 2x10s.

This is great advise. Just make sure to be conservative in the calcs since there will be some dynamic loading.

 

[orezok]

Just estimating: I would say my tractor, roughly #3500 lbs without bucket or backhoe or bh subframe and estimated 200 sq in contact patch for each back tire and 50 sq in for each front tire seems to be 1750 lbs on the back divided by 400 = 4.4 lbs per sq in in the back x 144 = 634 lbs per sq ft in the back and 1750 divided by 100 = 17.5 lbs per sq in in the front x 144 =2520 lbs per square foot in the front. Pretty large point load. Your floor decking will need to accomodate the point load. Area loading is roughly 5 feet x 6 feet = 30 sq ft, divided into 3500 lbs = 117 lbs per sq ft area load. Your floor joist will need to accomodat that. Without looking up load ratings, I would guess you would need at least 2x10s 12 inches on center with 3 layers of 3/4 inch plywood, with spans between supports no longer than 6 ft for the 2x10s.

Actually. it's much simpler than that. If you have 30 PSI in a tire, it will exert 30 psi on the floor. Every action has an equal and opposite reaction. Raising or lowering the pressure will vary the footprint, but the load will equal pressure.

 

[carpenter383]

I would just figure out where the tractor will be in the building and strengthen that section of floor from the door to the tractors' resting place. Set posts under the floor with beams on top of them that will support the bottom of the floor joists.

 

[CurlyDave]

If you have 30 PSI in a tire, it will exert 30 psi on the floor.

This is a common misconception about tires and how they work.

A tire works by the air pressure inside stiffening the sidewalls, which are the primary load-bearing mechanism.

If you increase the pressure in a 30 psi tire to 60 psi, the area in contact with the ground will not be cut in half.

 

[wedge40]

you have gotten my curiosity. Is there a reason you need to use lumber for a floor for your tractor ?

I'm going to guess it's taxes. Most states/counties charge taxes on a permanent buildings but none on temporary building. Cement = permanent, wood = temporary. I bought one those little tin cans at the local home improvement chain. I think 10X14 and decided I wanted a raised wood floor, but I was going to put my cub cadet garden tractor in there. I believe I used 2x8 on 12" centers supported every 18". When I first got done I had put down 1/2" treated plywood and the floor sagged in spots when I was walking on it. No way was this thing going to support my garden tractor. So I went back and got another layer of 3/4" ply to put down. I dont think I trust driving a car on it but it don't budge at all when I drive the cub on it. I think the shed kit cost about $500 or $600 and I ended up with well over a grand in the deck. Dont get me wrong I'm still glad I did it because when I get the barn done it will be easy to tear the shed down.

Wedge

 

[Charlton John]

I have a wood floor in my pole barn. My tractor weighs roughly 3k w/ loaded rears,fel and the BB on the back so not quite as heavy as yours, but I do also have plenty of other toys in there as well. My floor is constructed of 2x6's but 6" OC w/ 1" ply screwed and glued. The floor is extremely strong I could drive a truck on it I beleive w/ no issues.

 

[WVBill]

My floor is constructed of 2x6's but 6" OC w/ 1" ply screwed and glued.

Good info - critical question, though - what's the unsupported span of the 2X6's?