How do I engineer a floating mezzanine storage floor for my storeoom

[postie101]

I've got this storeroom that's been added on to the house at some stage. The wall on the left is the original exterior wall, and I believe the construction is double brick all around.

The space is very small, so I'm looking to add a mezzanine floor for storage. It needs to be above head height - I'm imagining it going roughly where those existing boards up on the wall are, just needs to be big enough to storage storage bins, xmas tree, etc. Most of the stuff in photo would ideally end up being stored there, aside from lawn mowers of course. Would certainly need to be able to handle me climbing up there to grab stuff.

Since the space is so small, I'd really like to use a floating design - having a box frame would make things even more cramped. It's an old house, and none of the walls seem to be particularly plumb either, which I imagine would complicate things if trying to build in a frame.

The span would be just under 1.5m, and the platform would be just under 1.5m in depth also. The depth might end up being slightly increased (~1.75m), let me know if this changes things at all.

What timber / fixings should I be looking to use for this?
I've found this article, but not sure how reliable it is.
https://www.bhg.com.au/homes/diy/build-a-mezzanine-garage-storage/

A lot of the designs I've encountered are based off a stud wall - I've got masonry all around so want to make sure I'm doing things right.
Cheers 👍

[JacobZ]

Hi @postie101,

A warm welcome to the Bunnings Workshop community and thank you for your question.

If you are looking to have no posts and the structure is supported entirely by the walls, you would need to speak with an engineer to ensure the walls are capable of supporting the additional load, and that the waling plates are attached to the brick in a suitable manner to support the load applied to the waling plates. I understand it is more desirable to have a floating mezzanine, but we need to be sure it is safe for purpose, and the only way to do so is to speak with a suitably licenced person.

Adding some timber posts and simply bolting the structure to the walls to keep it rigid and in place would negate the need for an engineer's assessment and is likely a better option as it would not put the job of weight bearing on the brick walls, they would only be used to hold things in place laterally. 

As what you are doing is essentially building a raised deck, if you use posts, you can base your design on the principles outlined in How to understand deck components and How to understand deck span tables. 

I'd suggest using 4 x 90 x 90mm Posts attached to the concrete with Pryda 90mm M10 Bolt Down Post Anchors and Ramset 10 x 75mm Galvanised AnkaScrews. 

You can then use 190 x 35mm Outdoor Framing for your bearers and 140 x 35mm Outdoor Framing as your joists. You will need to use Pryda 140x35 Joist Hangers with Pryda Timber Connector Screws to attach the joists to the bearers.

I have thrown together a basic render showing how it would look. 

   

Let me know what you think and if you'd like further guidance on the design or materials, please don't hesitate to reach out.

Jacob

[postie101]

Thanks very much for your detailed reply mate, that’s very helpful. 

Point taken on checking with an engineer re floating design. Follow up question regarding this - how do I find one? Are there businesses that provide this kind of service for small scale residential work like this? What would be the search term I should use to find one?

[postie101]

Have been looking into the possibility of box framing it, pulled up one of the brick pavers that make up the floor to have a look at what’s under there.

Looks like theres a concrete (?) base of some description under there although I’m not exactly sure what it is. It’s the same material as what appears to be under my driveway pavers. Photo attached although it’s not particularly descriptive.

I’m not exactly sure what this material is. I also don’t think it looks to be particularly level, as I suppose the paver base was managing that (albeit poorly).

Would you see any issues with fixing the box frame vertical posts into this? Again, walls aren’t exactly plumb either (joys of 1940s house).

Thanks!

 

[postie101]

I just realised that’s probably a no go regardless, because I’ve got a stone foundation at the base of the wall that extends beyond the brick wall anyway (as I mentioned the left side wall is the original exterior wall of the house).

That would stop me from being able to get the post flush up against the wall.

Seems like theres a few complications to this one! Maybe a professional casting their eye over it and recommending a way forward is the way to go.