Building a media cabinet

nashant · 22 Jul 2015

**Also posted in design section, but this seems to get much more action**

I'm about to undertake my most ambitious project to date and I wanted to ask some advice.

Firstly, I've attached a couple of images of the design. Do you think that it will be structurally sound? At some point in the future doors will be added to the upper, side and lower units. Will it still be ok?

Secondly, about joining the boards together. I don't want any screw heads or anything visible, so they would be fine for the back panels and interiors but not for the external side panels. Would you recommend using cam lock and dowels along with wooden dowels and glue? Or are screws, with some way to cover the heads, essential?

The total weight of the upper section of the unit is 48.9kg and it's holding a projector screen weighing 9kg along with whatever else gets put in the cupboards, nothing too heavy. The weight of the doors would be 11.8kg total. So total weight will be close to 70kg before storing anything in the cupboards.

Any help would be greatly appreciated!

Front:

Back:

custard · 22 Jul 2015

nashant":22hcwpfg said:
Do you think that it will be structurally sound? At some point in the future doors will be added to the upper, side and lower units. Will it still be ok?
The total weight of the upper section of the unit is 48.9kg and it's holding a projector screen weighing 9kg along with whatever else gets put in the cupboards

The top section will sag, unless it's fixed to the wall or supported by wall mounted cleats it'll bend like a banana and pull the upright sections out of true. If you're planning on using MDF it's even less likely to be satisfactory,

http://www.woodbin.com/calcs/sagulator/

By the way, the idea that shelving will only be used for light items is an urban myth! I did a job once where the client insisted on floating shelves, I emphasised that a number of features of this particular location made floating shelves a bit suspect. "That's okay", the client said, "we understand and it'll only be used for extremely light items". I went back a year later on a follow up job and on the shelves were about 30 kilos of books and a decorative vintage weighing scale complete with a full set of cast iron weights! I made a point of commenting on this and actually took a surreptitious snap on my phone camera, as when the whole lot comes crashing down they'll swear blind there was just a bag of cotton wool balls on the shelves.

Adding doors as an afterthought is just storing up problems, if you're using cup hinges you'll want to drill the individual components while they're flat, if you're using knife hinges you need full access to mortice in the hinge, if you're using butt hinges you'll need a solid wood lipping to take the screws. Sure, an experienced man can, at a push, work around all these problems. But by your own admission you're not that experienced man!

nashant · 22 Jul 2015

I am certainly not that experienced man! I will indeed be using cup hinges. I guess I'll just pre-drill the holes now and then add the doors later.

Decided on using those blue GripIt http://gripitfixings.co.uk/product-range/#25mm fixings to secure the upper back plates to the wall, 2 fixings each which should have a safe max load of 180kg each side.

Racers · 22 Jul 2015

As for joining I would use biscuits or dominos, dowels you need to be accurate in two planes where as biscuits you only need to be accurate in one.
Even if those fixing can take the load it will still only be supported at two points, plenty of distance to allow sag, use many fixing to spread the load and support the shelves.

Pete

Zeddedhed · 22 Jul 2015

If I was doing this I would try and work out how to get the shelf of the top section fitted AFTER the cabinet was fitted, and then hide fixings behind the shelf.
As the guys have said there will be considerable weight there and it WILL sag unless properly supported. I'd try and get a good fixing in every 200mm or so, as I said from behind the shelf through the back into the wall.
I would also try and ensure the dividers are securely fixed to the base panel of the upper unit and the shelf above, the upper divider securely fixed to the shelf and top panel, and the shelf fixed through the sides - in other words try and fix EVERYTHING to EVERYTHING it touches.
If you're making it from a wood veneered board then you can cut some plugs and flush them off.
If it's MFC then the only way to hide screws that I've found is to use those nasty brown screw covers.
Someone once told me that you can use wood plugs covered in a piece of the MFC edging but I've never tried it s can't comment.

nashant · 22 Jul 2015

The lower shelf is actually in 2 parts, front and back, with a space for a projector screen between. I'm going to leave the front shelf off to start with, fix the unit to the wall in the space in the lower rear shelf, mount the screen, then attach the front shelf with dowels and cam locks.

These Grip It fixings, the 25mm ones, have a maximum sheer force of 180kg with a safe load of 90kg each. I'll stick 3 in each back plate which surely should support it fully. The top section is never going to hold anywhere near 540kg including its own weight. I might get a piece of timber to support the top section wile I'm fixing it to the wall.

Everything will be fixed to everything and I'm sorting out the order in which everything gets fixed together now. Gonna get an extra couple of metres of edging and make little screw caps out of them.