MDF or MR MDF 18mm or 12mm for building dvd storage shelfves

[Mcluma]

I will be building a large amount of shelving for holding up the collection of DVD’s around 3000. in our cinema room

The walls I will be attaching/placing it to will be 8mtr long and 5.2mtr long, the unit will be 4 shelves high with a plinth of 150mm (with rope backlighting)

I will be constructing shelves which are going to be around 1500mm long, at every 1500mm interval there will be a large bulkhead column of 400mm square (to display collector items etc) So on the 8mtr wall there will be 5 bulkhead columns and 4 series of shelves

on the short wall it will be shelves of 1200mm length with 4 bulkhead columns of 400mm square so total 5200mm

The units will be painted in a gun metal grey colour (dark)

What is best to use:
Plain MDF or MR MDF?

Then is it ok to use 18mm mdf for the shelves and carcass of the bulkhead column and then the back of the shelves in 12mm mdf?
DVD’s are not as heavy as books and the depth of the shelves will be around 180mm.
Is it best to still have a middle post to support the shelves from sagging?

Thanks for the advice

 

[AndyT]

I think that DVDs in cases are so light that you could plan this around the sagginess of the material unloaded and get the same answer. 1500 mm between supports sounds rather long to me. I think 1200 mm would be ok, especially if the shelves are going to be fixed to the back board.
If you don't intend fixing to it (or even if you do) 12mm for the back sounds unnecessarily heavy. You could use 6mm or even hardboard, as you are going to paint it.

The sagulator calculator may help, or just some experiments with sample shelves propped up and loaded.

 

[PeterBassett]

Shelves full of DVD are heavier that you think. Definitely lighter than books yes, but they still have a fair heft in bulk.

 

[9fingers]

1500mm is just too long for MDF which will sag under its own weight in time and look awful.

Intersperse with vertical dividers to drop the span to 750mm.

Use MR it will take paint so much better that ordinary stuff.

Bob

 

[Mcluma]

6mm for the back will work, i will be attaching the shelves to the back as there is no need for them to be moved up or down in height

 

[tezza111]

Agreed with most that has been said. 15mm-18mm is too heavy for dvds...they weigh nothing. Also people get fooled into thinking the thicker/
heavier MDF will work better.(not true)....as has been said it sags under its own weight and can be more of a hindrance the thicker you use.(under some circumstances)

Re the back panels.....6mm is fine if you don't need to add any integrity to the structure/shelves. If its just a blanking/finishing add on.

In your case they are quite wide 1500mm. I would make them at 750mm much easier to handle etc as carcasses and at 750 no chance of sagging 12mm if you no how

to fire a decent screw (carcass or spax) into them from behind to add the extra support. 6mm is nail gun territory....with this too you will need to be accurate but will add

little support to the shelves. Better IMO to use 12mm to the backs if support is needed

With Mdf.......the best bet is bringing it all down to manageable widths (to prevent sagging) and using the right thickness for jobs involved.

You can plant on faceframes etc with nail gun after to give false impressions if thickness of shelves etc..

T

 

[jasonB]

Fixing the 18mm shelves to a 6mm back will stop any sag along their length at the rear.

To avoid any risk of them wanting to dip at the front I would add one or two verticals, to give say 3No 500mm sections. These can be set back say 50mm from the front and if made the same thickness as a DVD case will not really spoil the visual look of a long shelf once all teh DVD's are in place.

Something like the way these shelves are divided into three.

J

PS how do you get any time in the workshop if you watch that many DVDs????

 

[woodbloke]

1500mm is just too long for MDF which will sag under its own weight in time and look awful.

Intersperse with vertical dividers to drop the span to 750mm.

Use MR it will take paint so much better that ordinary stuff.

Bob

Spot on...MDF and chipboard will sag under their own weight, never mind anything that's put on them. I'd go for a decent quality plywood, maybe about 15mm thick and then lip the front show edge - Rob

 

[chunkolini]

A useful link for shelf making The Sagulator http://www.woodbin.com/calcs/sagulator.htm
I make a lot of shelves, see www.coolshelving.com and have done my own static tests on sag before finding the sagulator and the figures seemd close to mine.
I rule of thumb is if you think it might sag it will, if you are not sure it probably will.
There are few more tragic sights than a sagging shelf.
At least in home decor.

 

[Mcluma]

I like the idea of using 6mm on the back, and the small strips at 750mm interval, i can make them the width of dvd, so they will not show. then i can also make the shelves of 12mm, as they will be well supported, it will make it all much lighter.

I will be building it all in the cinema room. I have set up the table saw and workbench. I cannot keep going up and down two flight of stairs to the workshop

Thanks for all the input

for MR or MDF what is the best glue to use, the yellow titebond, or PU. I mostly use PU because of it rapid setting

 

[jasonB]

I use the yellow titebond II

J

 

[Mcluma]

I use the yellow titebond II

J

Thanks, i gues its also easier to clean up

I wil post some pictures during the build