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

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 👍

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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.

MitchellMc

Hi @postie101,

That does appear to be concrete under the bricks, so you could assume that bolting to it would be fine.

It would likely be best to do away with the idea of you climbing on the area, as I would also have to support your weight. That takes away the risk factor of the platform collapsing with a person on it. Then, you'd only need to design it to hold the weight of the items and ensure the walls adequately support the beams. However, as you've mentioned, it might be best to employ the services of a professional to ensure the installation is adequate.

Mitchell

postie101

Sure, makes sense.

What about then having a ring of shelving around the exterior of the room? Would you be able to recommend a suitably heavy duty shelf bracket? Would need to be deep enough to fit xmas tree / those standard plastic storage tubs.

Cheers,
Lachlan

MitchellMc

Generally, stayed brackets are the way to go with heavier items @postie101. They can hold a substantial amount of weight and extend quite far out from the wall.

Mitchell

postie101

I've been looking at a mix of these two stayed brackets to suit the depths of the shelves on the sides / rear of the storeroom.

https://www.bunnings.com.au/carinya-600-x-300mm-black-twisted-stay-bracket-heavy-duty_p0212168

https://www.bunnings.com.au/carinya-400-x-350mm-black-twisted-stay-bracket-heavy-duty_p0212163

I'll likely end up using 4x 600mm brackets for the back wall and 4x 400mm brackets for the each side wall, with the shelf sizes cut to match.

On Carinyas website, the weight rating for these is specified as being with a 415mm spacing between two brackets. Is it possible to quantify the impact of upping the spacing to say 550mm to slightly reduce the number of brackets required? The weight rating for the 600mm bracket is 250kg - I'd prefer to over-engineer this but realistically I doubt Id even be close to approaching that, as I'll likely just be storing household items (clothes, books etc) on the shelves anyway.

In terms of fixings, I imagine dynabolts of some description will be the way to go. Would these be acceptable? Appears to be three fixings per bracket.

https://www.bunnings.com.au/ramset-6-x-75mm-countersunk-dynabolt-plus-masonry-anchor_p2269935

Finally, the required shelving material is slightly awkward in that I don't think a solo sheet of plywood will cover it (diagram of the shelf measurements attached). I want to use one continuous bit of material per shelf - they end up quite long.

Are you able to recommend a suitable material to make the shelf out of? Is it possible to go down to 12mm ply given the amount of brackets I'm using to save on cost, or is 18mm pretty much mandatory for this purpose?

Thanks much for your help so far.

MitchellMc

Moving from a 415mm to 550mm spacing would be negligible to their weight rating @postie101. Remember that's 250kg per bracket. If you have four brackets, that would be 1000kg spaced at 415mm centres. Even at 550mm centres, your brick wall would collapse before the brackets failed. You shouldn't be putting much more than 100 kg on the wall, as brick veneer walls are not designed to take side loads.

Those Dynabolts are exactly what you would use.

18mm ply or MDF would be the way to go as 12mm is too thin. I'd recommend cutting down sheets of CUSTOMwood 18 x 2400 x 1200mm Raw E0 MDF or SpecRite 2400 x 1200 x 17mm Film Faced Non Structural Plywood.

Mitchell

postie101

Great @MitchellMc. Just on the side load point - is the height at which I'm planning to mount these shelves acceptable? I count 8 courses of brick on the shortest wall (rear and left wall appear to have slightly more, sloped roof), above where I'd want to mount them. Is that enough for this purpose? I know more is preferable as they add weight to the brick holding the mountings which would reduce the chance of the brick getting pulled from the wall.

Potentially overthinking again as I would only have around 25kg-ish being held up between each bracket, but thought it would be worth asking.

MitchellMc

Hi @postie101,

I don't think it particularly matters too much where you put the shelves. Just don't go and load several hundred kilos on each shelf.

Mitchell

postie101

@MitchellMc So things are going well for the most part - I'm fighting against some fairly uneven brick walls though.

Can't blame this one on that though, accidentallyput one of my brackets up out of level. Doh.

Is this an acceptable solution? I'd be placing the ply shelf on top of those to level things out, and then screwing through the hole into the washer into the wood. I'm not sure about the structural validity of this approach though. I'm basically reducing the contact area between ply and bracket significantly.

Is that an issue and if yes, is there a better approach? Cheers.

EricL

Hi @postie101

I don't think it will be an issue as long as the timber shelf is properly anchored to the angle bracket. Since you won't be putting anything extremely heavy at the very top, the shelf should be fine. I recommend putting the empty luggage and other small items at the top so that it will not put a lot of stress on the shelf or bracket.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

Nailbag

Hi @postie101

I wouldn't be worried with that shelf being out a few mm off-level. It's very easy to do when drilling into brick as standard masonry drill bits have a habit of walking off the mark as you start the hole. And never trust that the brick's are level either if you're using them as your horizontal guide.

Using those washers as spacers to compensate for the variances in the brick facings is fine. But before tightening the screws fully, let the washers hang of the screw, not held centrally. Since the washer hole will be much larger in diameter than the screw, it will have the potential for the shelf to drop those few mm. For extra fastening strength, you could make the centre of the brick below then on the bracket. remove it and drill a hole a size the screw can slip through. Then mark and make another fastening hole in the brick.

I can't tell by this photo if you're using "stayed" brackets. This a much stronger than once that don't have an angled support arm. They come in a large range of configurations, sizes and colour.

Nairbag

Dave-1

Morning @postie101

Nice way to gain some space back 🙂

I do have a question about the bracket and teh way you have attached it to the wall tho.

What type of bracket are you using? If its the stayed bracket as @Nailbag had suggested then it should carry the load.

Im not keen on the rawl plug and screw that you have used tho. It would hold a shelf yes but not a mezzanine floor (Unless I have it wrong and you are just putting an extra shelf in?) I lile concrete screws (they go into brick very nicely) and I find they give a lot more support and last a lot longer. I havnt had one fail yet or even split a brick. The holes on the bracket would need to be larger is all.

Ramset 8 x 60mm Galvanised AnkaScrew Masonry Anchor just to show the type of screw I am meaning.

Dave

postie101

Hi mate, thanks much for your reply. That definitely has been my experience, I certainly underestimated how much variance the bricks would have in them and how much that would pass on to the bracket being square to the wall and level. Still fit for purpose (I’ll post some photos when all done), but it annoys the perfectionist in me.

So basically dont worry about trying to get the screw centrally in the washer, just let it sit up next to the metal?

Also I’m not quite sure I follow your tips about getting some extra fastening strength - are you talking about the washers on the wall face or the ones going on top of the bracket?

And yep, I am indeed using stayed brackets, linked previously in the thread.

Cheers,

Lachlan

postie101

Hi Dave,

Original plan was to put in a mezzanine floor, but in previous discussions ended up deciding to put shelving in around three sides of the perimeter of the room, leaving a gap in the middle for access. It’s actually a much more sensible idea, I’m glad I went with this approach.

Yes, I’m using stayed brackets (linked earlier in thread), and I’m using flat head 6mmx75mm dynabolts for the fixings (also linked earlier) - no plugs. I did also consider the ankascrew type - unfortunately these brackets have quite small 6mm holes for the fixings, so it’s quite limiting in what you can use. I think I did look and couldn’t find any suitable screw type fixings to fit. I guess i could have drilled the bracket fixing holes out a bit though.

Washer approach for levelling look fine to you?

Cheers

Dave-1

Morning @postie101

Ahhh bingo 🙂 makes more sense now. I must have misse dit in the thread. Yes the washer levelling is also what I would do (and have done so for one of my walls) I do like @Nailbag's explanation about letting the washers rest on the screw instead of holding them centered. 🙂 Much easier instal and long term makes sense as well.

I think the extra fastening strenth @Nailbag is mentioning is to drill another hole in the bracket that matches the middle of the brick it is against and then add another screw to hold the bracket.

Dave

postie101

Hi All,

Finished this project and thought I'd make a post to wrap up. Overall, I'm happy with how the project went. Shelves are up and plenty fit for purpose. They are super solid and I have zero concerns with their ability to hold weight - I wouldn't even be close to stressing the limits with what I've got up there currently. They free up a lot of floor space in the shed (that I'm sure I'll manage to take up again soon). Mission accomplished.

Will expand below on what went right, what I'd change / do better next time, and some details / gotchas for those looking to do something similar. Will also include a parts list.

What Went Right:

The overall design. Thanks to the advice of @MitchellMc and @JacobZ I moved away from the original plan, which was to be more of a mezzanine style floor. This would have been considerably harder to engineer / build, more expensive, and would've resulted in storage that was harder to access for only a small increase in overall capacity. Perimeter shelving approach is much better for the space.
Materials. The brackets and ply I used are both super solid. Happy with them for the price. Stayed brackets also have the added bonus of acting as further storage, as you can see in photos I can store long items such as brooms through between the wall and the bracing. The Dynabolts I used are strong and are doing the job, but are difficult to work with, more on that later.
With the tools I had on hand (one 900mm spirit level), I'm happy with how level everything is. The span of the long shelves is just over 1900mm, so minor variances make a difference. It's not perfect, but it's good enough.

What I'd do differently next time:

Just buy a laser level. The area I was working in was tight, not very well lit, I was up on a ladder the whole time, and was doing the install on my own. All this to say, I spent a lot of time awkwardly balancing my spirit level on brackets and scribing pencil lines on brick trying to ensure the shelves were level. It would've been so much easier to just get a laser line up on the wall once and be done with it.
Handle the dust better. When you drill one 6mm hole in brick, it doesn't seem to make that much dust, especially when you're just in a shed. By the time you've drilled another 35 holes, it's a different story. I had to spend a lot of time cleaning up afterwards. I would probably use a project like this as an excuse to buy a mini rotary hammer with dust collection - it would make things easier and cleaner.
The flat head Dynabolts I used - while they fit the small fixing holes on the brackets (there's no 6mm hex head dynabolt variant as far as I can tell) and look nice - are a bit of a pain to work with. They seem to use a different design from the hex head Dynabolts I've used previously. This is fine (they still work), until you need to remove one. Whereas you can generally remove a whole hex head bolt by tapping the threaded rod part all the way in and wiggling the whole thing out, with these, there's no threaded rod. Instead, the top part of the fixing screws into the bottom part - the part that expands out. This means that in removing them, you can only really unscrew the top half, essentially leaving the expanded part stuck in the wall. Takeaway here is make sure you get your fixings in the right spot the first time unless you want to spend a lot of time wrestling with these bolts to get them out.

Some further comments, somewhat specific to my situation but may be of use.

Do not underestimate how much variance there may be to your walls. My house is old, none of the walls are plumb / square to the floor, and even the bricks protrude out at slightly different depths. This can easily mean that even if your brackets are completely level in terms of their height, they may not sit plumb / evenly against the wall, which will throw the shelf level out. I did my best to sort this out with washers, but I should've planned for this more in advance.

And a really pedantic one - if you're getting your finished panels cut down at Bunnings, ask the staff member to cut them in such a way that leaves at least one finished edge, if possible. I have no complaints and the staff were great, but I didn't specify this and have one shelf with no finished edge. If I can be bothered I might paint this at some stage so it matches the others.

Thanks again to those mentioned already and to @EricL, @Nailbag and @Dave-1 for your help.

Photos of the finished project below.

Parts List:

Brackets: Carinya 400 x 350 x 30 x 4mm White Heavy Duty Stayed Twisted Bracket - Bunnings Australia & Carinya 600 x 300 x 40mm White Heavy Duty Twisted Stayed Bracket - Bunnings Australia

Shelves: SpecRite 2400 x 1200 x 17mm Film Faced Non Structural Plywood - Bunnings Australia + another smaller panel of the same stuff

Wall Anchors: Ramset 6 x 75mm DynaBolt Plus Flat Head Bolt - 2 Pack - Bunnings Australia

Shelf Fixings: Zenith 12G x 18mm Zinc Plated Self Tapper Pan Head Sheet Metal Screws - 20 Pack - Bunnings Australia

+ Assorted washers for spacers as necessary

Dave-1

Evening @postie101

Nice, so nice 🙂 Welcome back space! Looks like a nice job and definently a learning curve 🙂 Thats the best type of job I think when you have something that is already good and you figure how to improve on good! 🙂

Bet you stand there looking at it come Christmas time and you take down the tree 🙂

Smiling all the way to the bank!

Dave

JacobZ

Hi Lachlan (@postie101),

Nice work with the shelves mate. They've already opened up so much space which I'm sure is a great relief.

I can certainly vouch for a laser level in a space like this. They make things so much easier, allowing you to have two hands free to carry out the work.

Thank you for sharing the details of your project and congratulations on a job well done.

Jacob

Nailbag

Nice work @postie101 ands great use of vertical real estate for the storage.

Early last year I debated to get a laser level to help me on a renovation project when setting out T&G boards to all for sides of a couple of rooms. I thought I probably wouldn't use it again. In the end, I found an affordable rechargeable cross-hair one online. Not only did it speed the project up significantly, I have since used it a dozen times including marking the ceiling out for an LED skylight. I only wish I bought it years ago.

Nailbag

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