Mdf cabinet tops

[Wilson joinery]

Here’s an interesting (yawn) one for a Saturday morning. If you were making carcasses for some storage cupboards in the eaves of a property (they will basically be a triangular shape) what would you make the sloping part of the carcass from? The sides will be 18mm mdf. I was also thinking of using 18mm for the sloping top. Probably seems like overkill but it will help to firm up the structure. Also would you sit the sloping panel inside the sides or on top?? Forgot to mention that the span/width of the carcass will be around 900mm. Therefore would I need to fit any additional brace pieces under the sloping top even though it won’t be carrying any weight?

Cheers
Pete

 

[Doug71]

How tall are they? 18mm mm does help firm things up but also adds a lot to the weight.

A quick sketch might help people give opinions.

 

[Wilson joinery]

Hi Doug71 here’s a photo. They will be approx 900mm wide so that is probably the key measurement for whether there will be any sag or not (bearing in mind the sloping back will carry no extra weight). Within the carcasses there will be shelves also approx 900mm wide. I’ve heard people talk about lipping a shelf or fitting an apron. Can anyone explain what lipping a shelf means?

Best regards
Pete

 

[Droogs]

12mm or even 9mm will suffice

 

[Wilson joinery]

And do you not think there will be noticeable sag using 12mm over a 900mm span?
Cheers
Pete

 

[Droogs]

not if you have some half lapped cross timbers in the frame for the panel to attach to with finish nails. similar to the example below

 

[pe2dave]

Can anyone explain what lipping a shelf means?

Best regards
Pete

MDF or ply leaves a 'not nice' edge when raw. This is often covered up by gluing on an 18mm x 4mm strip of wood just to provide a 'real wood' lip to the carcass.
18mm if you're using MDF, just find strip that matches the sheet goods you've used. HTH

 

[blackteaonesugar]

Can anyone explain what lipping a shelf means?

I've lipped these veneered mdf shelves with Oak, but the lippings are wider/thicker than the shelves and so I guess that makes them an Apron lipping.
This adds strength and reduces any tendency for the mdf to sag.
I've also rebated them over to reduce the seen line on top and to increase gluing area.

 

[BrandonB]

18mm back panel. If you're attaching it to the sides you will need the thickness to gain a decent fixing on an angle. If you used 12mm or thinner you'd struggle to get a decent fixing into the sides when you've cut the back panel on the angle.