Firewood shed, dimensioning of girders and joists


Old 11-21-12, 09:56 AM
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Firewood shed, dimensioning of girders and joists

I am going to build a 7'x16' firewood shed to hold about 6 cords.
I am using rough sawn spruce lumber throughout.

For the floor I am planning to use two 16' long 8"x8" laminated beams spaced 5' o.c..
Each beam will rest on two 12"x12" post spaced 13' o.c.
The beams will be cantilevered 12" at each end.
The span of the beams between the posts is 12'.

I will cantilever the joist 8" on each side.
The span of the joists between the beam will be 4'4".
I am planning to use 2"x6" joists spaced 16" o.c..

The floor will be made out of 1"x4".

I am going to stack the firewood 7' in height.
I have estimated a floor load of 200lbs/sqft.

Is my dimensioning OK?
Will this platform as designed hold the weight of the wood?

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Old 11-21-12, 10:22 AM
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Welcome to the forums.

Why 1x4" flooring? My first thought would be 3/4" plywood.
Old 11-21-12, 10:30 AM
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I'm no engineer but it sure sounds sturdy enough to me. I guess the rough sawn 1X4 will be true 1" thick?
Old 11-21-12, 10:39 AM
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" Each beam will rest on two 12"x12" post spaced 13' o.c. "

Though your beams are a beefy 8" x 8" ......the span is quite long and could sag.

Would it be that difficult to add a 3rd post in the center of each beam?

Also.....what are these posts? .....what type of footing will be used?

And....although the span for the joists isn't too much......I would go 12" O.C.

It would only require a couple of extra 2 x 6 's ......and will be better since you're using floor boards.

Old 11-21-12, 11:05 AM
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I agree with Halton that the 8x8's are beefy... but since it is a laminated beam it will be stronger than an 8x8 timber, and will have more resistance to deflection than a timber would.

So just assuming the 8x8 beams are the weak link in your plan...

I couldn't find a table for 8x8 engineered, but did find a table where they listed a 6 3/4 x 8 1/4 laminated SYP at 609 lbs per lin ft, with a span of 12'. Assuming they are comparable, and you have 2 of them that would be 1218 lbs per lin ft. (multiply that by 12 and you get 14616 lbs for a shed that has 112 sq ft... so that comes to about 130 lbs per sq ft.) If your beams are actually 8 1/4 x 8 1/4, then they would be able to carry more load than the example above.

The place that is supplying you with the laminated 8x8's should be able to tell you their load capacity when spanned as you suggest.

But I also agree with mitch that the 1x4's sound like the weakest link in this plan. (assuming they are not t&g). If they are full 1" that's better. I'm guessing you might be spacing these floor boards so that the wood can get plenty of air in order to dry out?
Old 11-21-12, 11:25 AM
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Welcome to the forum.
I always thought the Canadian way of building a wood shed was to use 4'x4' wood skids.
Old 11-22-12, 09:25 AM
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Or maybe even forget about a wood floor altogether, and just use a compacted gravel base over some weed-block fabric. Use post and beam for the structural framing, setting corner and intermediate posts below the frost line, and go for it. Would save a ton of work, and gravel never rots (when rain or blowing snow gets in and melts). My current wood shed has a concrete floor, which also never rots. Good air circulation for the bottom courses of firewood is provided by placing scrap 4 x 4 runners on the concrete first.

Last place we had in WA state had a wood shed with a plywood floor of several different vintages. Someone had been making a career out of replacing small bits at a time, apparently as they rotted out. Poorly built, and even exterior plywood does not weather well in moist or damp climates.
Old 11-22-12, 10:17 AM
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Just to further BridgeMan45's post, the skids are used for the floor on packed dirt.
They allow air flow and keep the wood off the ground. I've stacked wood about 6ft high on them and never had any real issue.

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