Freestanding Mezzanine for Storage Advice?

[AkiraDIY]

I need some extra storage in my house and as I have high ceilings, I'm wondering if it would be possible to build a freestanding mezzanine out of wood?

Freestanding because it's an old tenement building and I want to keep drilling into walls at a minimum (joist hangers are not really an option). I've googled for ages and can't find any solid information. Wooden kits are either too small (glorified loft beds really) and the steel ones either too expensive and/or too large.

My room is 3m wide, so ideally I'd be looking to have a platform of around 3m wide, 1.2m depth at around 2.5m high. I would like to span the width of the room as I don't want a pillar/post in the center of the floor but at 3m wide, I'm concerned about sag.

Is this something that's even possible or is it too big a job for a moderate DIY-er?

 

[John D v2.0]

3m is not a big span, if you're not concerned about deflection and it's light storage even 4 by 2 would be okay. Your base would be more tricky as there are aspects of structural design you have to know about before you can consider them. Eg racking failure can be resolved with diagonals if you can't brace it off the walls but you also have to take care of the fixings you use.
If you have serious concerns or it's a commercial thing you might ask a structural engineer but mostly making sure everything is tied in well should be enough.
I think the construction is easily DIY able but the design is where I'd be unsure

 

[^woody^]

This sounds like a wide shelf rather than a mezzanine, and the biggest problem is ensuring that it looks like a house and not like an Amazon warehouse. 5x2 for the horizontals and 3x2 for the uprights, with a sole plate on the floor.

 

[scbk]

If you like the industrial look, just use some scaffolding

 

[Leofric]

Freestanding

1.2m depth at around 2.5m high

As others say this is more like a large shelving unit than a mezzanine floor , but surely it would be likely to topple over if it isn't tied in to the existing structure

 

[John D v2.0]

As others say this is more like a large shelving unit

I'd like to know where you buy your books from
Or is it shelving to store plasterboard full sheets (I'm just kidding i know even builders merchants use suitably rated shelving to store all the sheet materials!)

 

[AkiraDIY]

Sorry for the late reply, just back from a last minute business trip. Yes, I think a very wide floor standing shelf (or a very tall narrow table) is a better description of what I'm trying to achieve than a mezzanine. I've even considered scaffolding but think it might look a bit unsightly (I think I have a better chance of dressing up wood than scaffold). I plan to have some fixings to the wall to stop it toppling over, I just didn't want to hang all of it from the wall.

I plan to put stuff you'd normally have in the basement or attic up there (tools, suitcases, Christmas decorations, camping gear, etc) and occasionally the weight of me as I rummage through it. So individually light items, but collectively it may add up. Especially if I add some ikea cupboards or the like to keep it all neat looking, opposed to a pile of stuff.

Would 3x2 uprights and 5x2 horizontals be safe and not sag excessively? Currently looking at span tables for C24 lumber but struggling to get my head around how the load rating factors over the whole surface area. Does a load rating of 0.5kN/m2 mean it won't support the weight of a person over 50kg standing on it?