Thread: Some feedback on a bunk design

Gday Issac

Firstly I really like the design.

Although I'm afraid I can't be too much help as I too suffer from the same affliction. And with that in mind I would probably go for at least 15mm maybe even 18mm for the main components. I think dowels and screws would be fine or even biscuits for alignment and screws to hold.

What ever way you end up going I hope you post some progress pics up for us to see.

cheers
shane

Thanks Shane. Yeh I might bump it up to 15mm.

Based on my calculation, it's already hitting $1500 (Bunnings prices) just for the lumber using 12mm.

I'll definitely post up some pics

I'd be using at least 17mm simply to give yourself enough margin to screw/dowel with minimal risk of coming out the side if your drilling is off by a few degrees. Buy your ply from a proper supplier, it'll be cheaper than a hardware chain and you'll have more options as well.

Plyco has a Poplar plywood that's extremely lightweight and (from memory) cheaper than Hoop Pine of equivalent thickness

There's a few good suppliers of plywood who sell through ebay in Sydney. And better quality then bunnings.

I often use these guys. Trademaster Joinery

G'day Isaac, I used the heavier ply like mentioned about when doing a Thomas the Tank Engine bed modification for our first grandson and it's now on grandson number 3.
Do some shopping around on the ply prices; a few years back I helped a fellow forum member collect a trailer load of some furniture grade ply from the southern suburbs of Sydney.
Cheers, crowie

Just a suggestion there. You could put a draw underneath each rung of steps and turn one set of those drawers into a space for a wardrobe!
Also make sure the slats for the bed occupy at least half the area of the bed. (I got that info from a bed designer from Sealy)

Trademasters had good prices on ply BUT they wanted $250 for delivery of 3 sheets to northern suburbs Sydney. I ended up using Hardware and General at Brookvale. Prices weren't that much dearer for furniture grade ply and they had free delivery.

Originally Posted by izzy_a

Hi everyone,

Just finished designing my kids bunk bed and hoping to get some feedback as it's my first time making something this big.

I was thinking of using 12mm ply for most of the construction and using 140x30mm dressed pine for the bed frames. One thing I can never understand is how to determine the appropriate timber thickness for my constructions . Do you think 12mm is sufficient for the cabinet walls to hold up the upper bed? The cabinets have 3 divider shelves inside (12mm) (spaced out evenly).

23-03-2017 4-27-21 PM.png

What would be your choice of joint for such a construction? I want to do dowel joints with 6g x 40mm timber screws (pre-drilled) for extra support for the cabinets at least, but not quite suite.

Thanks in advance.

Isaac

Hi Isaac

You could build that construction using 12 mm ply, but there would be a fair amount of fiddling involved to stiffen the verticals enough to support the upper bunk. You will find that 17, 18 or 19 mm material will be easier to work with and importantly stiffer where used vertically. (Ikea is a good source for what thickness of board will work for a construction like the one you are planning, and where stiffening plates need to be placed between verticals.) My personal preference for paint grade constructions, like your proposal, is the 19 mm laminated pine panels sold by Bunnings and others. Laminated particle board would be a more economical choice but particle board needs an edge treatment, as does furniture ply. And attaching suitable edging can be a pain. I suggest that you do as much finishing as possible before you start assembling the panels.


Bed slats.
Nominal 100 x 25 Tassie Oak (which is about 90 x 19 finished) will be more than strong enough for the slats, and as mentioned above the slats need to cover about half the area of the mattress. (unlike pine, commercial Tassie Oak is supplied quarter sawn and thus better holds the load.)


Design standards
There are standards for steps up into bunk beds and for railings on the bed space to stop kids falling out which your design appears to lack. and I think you may also need a hand rail for the steps. Also, from here the steps look to be far too tall for a kid to climb easily.
But, if you don't mind, can I leave you to follow up what the design standards ?


Joints
Dowel joints will be satisfactory, but the rule of thumb is that dowels should be spaced 25-30 mm apart -- which for a construction like yours is quite a lot.

Using 19 mm thick material implies using 60 mm long screws. (using the one third / two thirds rule.) 17 mm material would require a 50 mm long screw.

I suggest that you use cleats to attach the treads of the steps be attached to the sides of the cabinet, and the outside vertical.


other design comments.
The compartments you have drawn appear too deep to be particularly useful. My own experience is that drawers shouldn't be more than about 150 mm deep otherwise clothes just get lost in the bottom.
The higher level compartments are also difficult for smaller sized adults to access easily -- and impossible for kids.

Lastly, I suggest you incorporate construction rails and a plinth, see attached.

Originally Posted by ian

Joints
Dowel joints will be satisfactory, but the rule of thumb is that dowels should be spaced 25-30 mm apart -- which for a construction like yours is quite a lot.

Using 19 mm thick material implies using 60 mm long screws. (using the one third / two thirds rule.) 17 mm material would require a 50 mm long screw.

Dowel spacing "rules of thumb" vary wildly depending on the size of the pieces involved; chair frames might be as low as 17mm, tables and sofas can be pushed up to 30mm, but something that big should definitely NOT be spaced so closely. Aside from the hassle of setting out so many holes, the friction that will need to be overcome to knock up such a construction will be so great that I can pretty much guarantee that pieces will be broken in the process and if one is off by 1mm you may as well start again because it's simply not going to go together - speaking from experience here. Spacing can be safely bumped up to 70+ mm for the treads, providing that there is a minimum of 4 dowels per end, and very wide pieces like the head and foot can be well over 100mm spacing.

Those numbers are based on 50x10mm hardwood dowels.

Also, 50mm screws are 100% fine in 19mm ply as well as 17mm.

Hi Izzy
This looks line a wonderful project.

Just a few observations ... I see there are 4 steps ... a comfortable step riser for an adult is around 150 to 175mm with a 250mm tread. Four steps would get you to less than 800mm ... is that sufficient head space for the lower bunk? I would think that at least 1200mm would be expected. I would be looking for hand rails as well. Sleepy kids and steep big 300+mm risers may be a mismatch.

Rather than 18mm ply walls ... which will be super heavy (and expensive) why not look at a 70 x 35 frame stiles with similar sized rails, and a 6mm MDF for infill panels (I thought you said it was going to get painted anyway). Nice mortise and tenon joints (with draw bore dowels) would be super strong. I'd save the 12mm panels for steps and the drawers (with say 6mm bottoms) and MDF drawer fronts.

A design issue is in how it will be put together ... which are the modules which will bolt together on site to enable it to be shifted to another room/house or location? The steps will certainly give it stability from toppling over when to child in the top bunk leans over the side to annoy his/her/sister/brother below. 18mm ply for the top bunk would be a good use of that material ... sitting on Tas Oak rails for example.

I agree with the previous comment that the top drawers are too high for youngsters .. dont want them climbing up drawers. Why not utilize the space under the bed .. and open up the ares of the top drawers for more light to the bottom dweller?

A light above the lower bunk might be handy too

Go for it ... and keep the WIP pic coming in.

Regards

Rob

Hi all,

Thank you so much for the responses and great source of information.

I will need to do a quick redesign based on 17mm ply for the verticals. The slat measurements that I have is 65x19mm which I measured from some existing beds at our place. I'll definitely source out the Tassie Oak.

The total height of the stairs is 1200mm so with 300mm high per step and 335mm deep - do you guys think this is ok for a 5 year old to step up or too much of a mountain climb?

Ian, I'm not too fuss about the step up into the bunk bed because that side (plus the bed head side) will be against the wall. You are absolutely right regarding the drawers being too deep. I may need to redesign and split into shelvings at the back of the drawers for the lower bunk.

Rob, the frame stiles would be another option and sounds like it'll save me some $$$.

FYI the total height is 1690mm (floor to top of bed head), the head space of the lower bunk will be 800mm which i think will be plenty.

Thanks again everyone!

Kind regards,
Isaac

Originally Posted by izzy_a

The total height of the stairs is 1200mm so with 300mm high per step and 335mm deep - do you guys think this is ok for a 5 year old to step up or too much of a mountain climb?

That's waaaay too steep, Australian standard is 225mm maximum height... and that's for adults.

Assuming a height of about 110cm for an average 5yo, 300mm is around knee high, so it'd be similar to an adult climbing stairs about 500mm high

Are those Australian standards based on normal house stairs? I've been google image searching on "bunk beds with stairs" and if not all have 4 steps. I doubt they can achieve the 100-200mm mark - I think the idea behind steep steps is for the kids to enjoy climbing or wear em out so go to sleep faster?! Just my theory.. lol

Yeah it's for normal stairs. You do have a point with wearing them out :P