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How to build a bed platform or mini mezzanine?

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Hi brains trust,

I don't know how to put this succinctly, so please bear with me.

The pictures above depict my small bedroom in my small one-bed flat and a table-height platform I would like to build to create more storage and a bit of visual interest. I want it to feel more like a raised bedroom than a loft bed, so my current bed would sit atop the platform. Sort of like this:

In time I will devise steps for the top right and bottom left of the platform, so it can be accessed from two sides by two people -- but that's a project for another day. Right now, my priority is getting it built, properly, and using the storage space below.

I want the top of the structure, sans flooring, to be 730mm high. (With subfloor and eventually finished flooring, I anticipate the top of the platform being 760mm high). This allows me to comfortably stand on the platform without hitting my head and it won't obstruct the window.

Now my main questions relate to the type and spacing of lag bolts and post(s) and timber sizes.

From the modular decking panel (I) in the shopping list below, I determined that given the height of my platform 90 x45mm timber would be adequate for the frame. Is this a fair assumption? I was seriously considering using these for my project, not least of all because I could fit four of them in my car, but the measurements aren't quite right and it'd cost my about four times as much.

I know I'll need 100mm lag bolts for the two beams (bearers? I get confused sometimes!) to be attached to my brick walls, but I'm not sure how many or how best to lay them out. Can anyone help me figure this bit out please?

To make things a little trickier for myself, I would like to curve the bottom right corner of the platform. That's why I have tentatively drawn two posts connected by a diagonal piece of 90 x 45mm timber. I would create the curve by slightly cantilevering the flooring. Would that work?

Also, should I consider putting perpendicular supports between my joists? Or would I be overengineering by an unacceptable degree?

Finally, should I be using joist hangers or could I get away with a hole jig and screws? If the latter, what type, strength and length (and angle) of screws should I be using. I get the impression 'decking screws' are more for connecting floors to joists as opposed to securing the joists to the outer frame, but I may well be labouring under a misapprehension there.

Finally, my shopping list below includes a few items (A,C + I) that I no longer intend to use for this project but which helped me get to this stage in my planning. I think I will add another two 2.4m lengths of the 90 x 45mm, to allow for errors and/or create joist supports if advised, and obviously need to add all the screws, hangers and other hardware I might need.

Anyway, if you've got this far, I really appreciate your time and any wisdom you can impart.

Cheers!

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EricL

Hello @CB123

Thanks for sharing your question about building a mini mezzanine platform. The 1116 x 1116mm Modular Decking 90 x 45mm Base Frame Assembled should be sufficient for framing. However, the modular decking frame has been designed for low level applications.

If you are anchoring it to your masonry wall and are planning on having it higher than half a meter. I recommend engaging the services of a registered builder or handy person. They will be able to tell you how many bolts will be needed for your wall and how many support posts will need to be placed underneath the frame.

Please keep in mind that your mini mezzanine will need to support weight of your bed, a minimum of two adults and any other appliances you might wish to include on top. The mini mezzanine will also need to be able to put up with dynamic loads applied to it.

In regards to the materials you've chosen, I recommend using the STRUCTAflor 19 x 3600 x 800mm H2 Treated YellowTongue. For your post, I suggest 100 x 100mm 2.4m Post GL13 Merbau Laminated Select Grade DPR KD. As for the bolts, I suggest Ramset 300ml Chemset UltraFix Plus in combination with Chemset anchor stud.

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

If you have any other questions we can help with, please let us know.

Eric

Dave-1

Afternoon @CB123

Wow, that will be an interesting mezzanine area, before you start have you considered that by raising the level of your bed it actually will get a lot warmer. I have slept in raised beds before and fair enough they were closer to the ceiling then what your plan is but I did end up with a headache from the heat.

The list of items that @EricL has suggested is the way I would go. That curve you mention made me think of how much space between the frame you are building and between the wardrobe and bathroom. 620mm is too narrow I would strongly suggest. I have had discussion with loads of people at work about distances between objects and access and people always tell me "it will be fine" then I have gone back to shift them as they find it too tight.

If you are certain it would be acceptable I would then suggest you place something solid at the distance of 620mm from the robe and then go through the motions of picking something off the floor in the robe. It just helps you picture what could be an issue before you start.

A solution would be to build a "stand" that is the 700mm that fits exactly under your bed, that way the footprint of your bed verse the rest of the room will still work.

Dave

CB123

Thanks @Dave-1 and @EricL,

I really appreciate you input.

I currently have a bedside table that is only about 400 from the robe, so I think I can live with a 620 walkway, but I will take a bit more time to test it and be sure before I get the hammer drill out!

I picked the current dimensions because of the flexibility in layout and bed size it provides. Any narrower than 2100 and I could never upgrade from my current double to a queen. But yes, the curve idea was to minimise any knocking into sharp corners that may occur.

I am very used to small space living, having done the van life thing for a bit and once bolting three pallets racks together to create a loft bed base in a studio I was renting. So I should be OK with the heat thing.

(A little off topic, but in the fullness of time, I would like to knock through the wall between the robe and the WC, and move the WC into the main bathroom section as currently I see the separation as a lot of wasted space that could go towards a walk in robe.)

Back to the topic at hand, I note the 1116 x 1116mm Modular Decking 90 x 45mm Base Frame Assembled states it is capable of supporting decks up to 770mm high. I assume that's been load tested to support several people and pieces of decking furniture at that height and have planned what I have so far based on that assumption. Will I get similar results using the 90*45mm untreated structural pine lengths in my shopping list?

I'm not opposed to the decking kits, but they're not quite the right dimensions for my space and will make the project more expensive. (I'm not totally cheap, I just have a fixer upper that needs everything doing!)

As for the number and spacing of the lag bolts, I'll chat to some builders and have a read of the specifications for the bolts you've recommended.

EricL

Hi @CB123

In regards to the 1116 x 1116mm Modular Decking 90 x 45mm Base Frame Assembled, it has been load tested. However, your builder will decide how many support posts will go underneath.

The 90x45 is stated as untreated structural timber MGP10 and can therefore be used for framing.

If you need further assistance, please let us know.

Eric

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