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I am wanting to build a wardrobe that has a clothes hanging rail at the standard height and a shelf above. This will be a 3 door, box-carcass design featuring a double width and a single width carcass.

I am planning to build with Melamine faced fibreboard (MFC).

My dimensions are to be as such: enter image description here

I am planning on having a single, full-height door to enclose both the top and bottom sections.

My concern here is how I should go about building the top section. I am worried that a span of 960mm simply butt jointed may not be strong enough, or if the glue & screws do hold - that the weight of items on the shelf will cause sagging... Though I do imagine that top of the wardrobe should counteract any sagging.

With my concerns above, I have thought of building in one of two ways:

1 - Butt joints: This way I can get the top, middle and bottom of the carcass all cut to the same lengths for simplicity

enter image description here

2 - Separate boxes for top and bottom sections: This would mean a double thickness and greater rigidity for the bottom of the top shelf, however this may look odd with a thicker section when opening the door.

enter image description here

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  • I don't know the acceptable load capacities, but anecdotally, I have a single MDF shelf in the alcove next to a chimney breast, slightly bigger, 120cm. Mounted on three sides via 1" square timber solidly plugged & screwed to a brick wall & with a decorative 1" deep front-mounted 'architrave'. It sagged. Not much, but it has. I have one even larger with a big TV on it… it's marine ply & has a centre support. No sag.
    – Tetsujin
    Jan 24 at 11:06
  • @Tetsujin what type of centre support is it that you have used?
    – physicsboy
    Jan 24 at 11:57
  • Another piece [actually two because it worked best cosmetically] of the same marine ply as the shelf - making overall a T-shape off the floor. [or TT shape. The gap between the two is the exact width of my sub speaker; I built wheeled box shelves out of lighter ply each side, to get all the TV/hifi kit in & out easily] If you copied that, though, you'd just end up with 3 identical narrower compartments. Not really sure what else to suggest, except the 2-ply box version. I don't think 1-ply MDF will be strong enough… but it will depend on whether you have 6 jumpers or 6 old hifi amps up there;)
    – Tetsujin
    Jan 24 at 14:02
  • Ah I get you. Yeah I can't imagine that I'm going to put anything toooo heavy up there, just the general stuff that gets shoved up top a wardrobe to get out of the way. Anything big and heavy can go in the loft (when I get that boarded out.
    – physicsboy
    Jan 24 at 14:50

1 Answer 1

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Cut dados in the sides and back panels then glue your shelves into the dados. I'd suggest that you cut stopped dados in the sides, then notch the shelves. This way, you won't see the dado in the vertical carcass side every time you open the door.

You don't indicate how thick your carcass material is going to be, but generally dados are one half the thickness of the material they're being cut into. If your material is 20mm thick, then your dado should be 10mm. (Note: I'll use a 20mm thickness in other examples later. Adjust all numbers to the actual thickness of your material.)

With a dado, you'll have full support along each side of the depth of the shelf, and full length support along the back. That will go a long way toward preventing sag, but, most likely, not far enough.

To further help prevent sag, cut an additional piece of your material and use it as a stiffener along the front edge of the shelf. I'd suggest making it 40mm wide. Cut a 20mm rebate/rabbet (depending on which side of the Pond you're on), 10mm deep along one edge of this stiffener. Then mount this vertically at the front (door) edge of the shelf. This will give you a 20mm vertical piece to support the bottom front edge of the shelf. It will have the added benefit of having the melamine facing covering the cut edge of the fiberboard, so it will look nicer.

Here's a nice ASCII art drawing of the side profile of the vertical stiffener:

    | 10mm | 10mm |

--- +------+  +--------------------------------------------
    |      |  |
 20 |      |  |  This is where the shelf sits. 
 mm |      |  |  Gap for clarity in the drawing only, it should be tight
    |      |  +--------------------------------------------
--- |      +------+
    |             |
 20 |             |
 mm |             |
    |             |
--- +-------------+

Finally, I'm not certain exactly what "fiberboard" means where you are. There is quite a variety of terms for the same material, and these can vary not only by country but by region. To me "fiberboard" doesn't sound like particularly sturdy stuff, so I'm guessing it means something different to you and is actually suitable for building a cabinet like this.

In general, standard PVA carpenter's "wood glue" (yellow or white) would be sufficient to hold this thing together. The dados and rebates add significant gluing surface and that will only strengthen the joints. You may want to add screws for additional security, but be sure you're using the proper screws for this material. It's possible that a standard wood screw may not hold very well in this material and would almost be worse than no screw at all.

I'd also suggest pilot holes for all your screws. Any building product made by compressing fibers/wood chips/sawdust together with glue at high pressure (that I'm aware of) just aren't all that good at taking screws driven directly into them, especially into the edges. There is a strong tendency for these types of products to blow out as the screw forces its way in. The pilot hole will remove the majority of the material meaning that the only part of the screw needing more room are the threads which are designed to cut nicely instead of being a blunt force weapon.

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  • Additionally, this question would probably have been better suited at Woodworking. Particle board/fiberboard furniture certainly isn't "fine woodworking", but cabinet building definitely fits into their purview, even if the raw materials aren't the "best". Also, lots of cabinets are built with plywood carcasses and only have fancy doors and drawer fronts, so no insults implied or intended.
    – FreeMan
    Jan 24 at 17:46

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