newbie first thread: shed floor joists

[unwaxable]

hi all
I'm sure this will have been done to death, but here goes anyway.
Iam planning a shed built on concrete piers dug about 400mm deep and about 100mm above ground.
the shed is to be 4m by 3m, with a 4m by 2m decking in front of it all on a single frame.
I will use 100mm square bearers, bolted onto the concrete piers, spaced at 1.5m, is this too far apart?
On this sled of bearers i plan a frame of 2x7 inch joists at 500mm spacings, with vertical corner posts of 125mm square
I know that 400mm is recommended but this shed is strictly a shed for lawn mower and push bikes etc: i already have a workshop, this will never take any serious weight.
am i pushing my luck?
I have read a seven inch beam is good to span fourteen feet.
the shed walls i am planning to build using 2x4's spaced at 400mm
likewise for the roof trusses, 90mmx38 beams and CLS again spaced at either 500 0r 400mm.
Any pointers will be greatly appreciated .
I am now waiting for a break in the weather to start digging the holes, ballast and mixer arrive tomorrow.
all the mistakes i made on my previous workshop build i am avoiding:
this should turn out to be a quality build, looking forward to it.
good evening, all

 

[MikeG.]

Welcome to the forum.

.......I have read a seven inch beam is good to span fourteen feet...........

It isn't. Where did you read this? As I understand your proposal, you haven't got to span 14 feet anyway.

You have completely under-specced the floor, over-specced the walls, and I have no idea of what design of roof you are proposing so can't comment on that. I suggest you do a quick sketch (you may need to make another couple of posts before you can post images).......plans and elevation/s........and then we can set about sorting out this structure of yours.

 

[nev]

Welcome

I don't have the knowledge to comment on your specs but I would suggest one thing.
The one thing I do know is that (typical treated softwood) decking invariably rots. For that reason I would make the frame of the shed and decking two separate items, supported on the same posts if you like and butted together for a seamless look, that way when then the decking gives up and needs replacing you don't need to disturb the shed.

 

[unwaxable]

mike g:
thank you for your reply and willingness to advise.
i accept that i may have proposed spacing the main 4x4inch bearers too far apart,
i planned on three runs, each 2m apart with 1.5m spacings along each run, therefore 12 posts in all.
this would run along the length of the build, 3m shed and 2m deck, both 4m wide.
what do you advise as suitable spacing for these posts?
i am hoping to be digging this week, but happy to revisit the drawing board for the sake of getting it right.
i have made quite detailed plans but not sure yet as a newcomer to this forum about submitting images etc.
the roof i plan on making consists of trusses spanning across the width of the shed, overhanging by 200mm each end, so will be 3.4m with apex of 1m in the centre, made from CLS beams of 90x38mm and 63x38mm.
thanks again for your help, I hope this makes things a little clearer.

 

[MikeG.]

Please have a good read of the first few posts in each of the threads linked to in my signature, below. And whilst your description of the layout of structure makes sense to the person who designed it, I need a drawing, please. I'm an architect, and have run into issues hundreds of times trying to understand people's descriptions of their ideas. Sketch it, scan or photograph it, and post it here. As I said, you may need to post another post or two before the forum software accepts that you aren't a spammer, but a simple reply or two will quickly get you there.

 

[unwaxable]

Thanks Mike, i will supply drawings shortly
regards, Peter