MDF Carcass advice for a newbie...

[NathanJT]

Like many before me I'm sure, I'm looking to expand my horizons a bit as far as DIY is concerned and replace some old fitted wardrobes.

The area in question though poses me a bit of a problem.

I intend to go the route of a plinth with MDF carcasses. My issue though is that the depth of the alcove the wardrobes need to go in is only 57cm. At the moment the wardrobes that are there are framed out at the front with a full length shelf to provide rigidity. That doesn't work for us though as we want to have drawers and shelves in there to make the space more efficient.

I'm limited therefore on the depth of the wardrobes and my question is with regards to the backing matterial of the carcasses. I'll be using 18mm MR-MDF for the base, sides and shelves in the build, but to reduce the amount of space lost, front to back, I was thinking of going thinner for the back pannel.

There will be 3 larger carcasses of 1900x900x570 and one smaller of 1900x450x570. Two of the larger ones will have an off center middle "shelf" to act as the top of the drawer frame. The other will be full height hanging space. Above these when finished will be matching top boxes up to the ceiling (about 2.4m).

I've built plenty of PAX wardrobes over the years and realise that the torsional rigidity of those is provided by a rather thin piece of nailed on chipboard. So, how thin can I realistically go for the back panel? 12mm, 9mm?

Many thanks in advance.



Nathan.

 

[rogxwhit]

If they're in alcoves can't you just fix to the side walls and omit the back panels?

 

[Bingy man]

I’ve not built wardrobes but the kitchen I’ve fitted have approx 6-8 mm mdf back panels- smaller dimensions 1000x800//600x600 etc so given the much larger sizes you have quoted then 12 mm is less likely to flex across those dimensions especially if your fitting these panels in one piece ( no centre post)

 

[NathanJT]

If they're in alcoves can't you just fix to the side walls and omit the back panels?

There will be about a 8cm spacer down the sides and it's not really practical to add braces unfortunately.

 

[rogxwhit]

You could use a 6mm backing panel especially if it could have an intermediate fixing (or two) eg to a fixed shelf to stop it being too 'flappy'. It would function for anti-racking as well as anything thicker.

Why MR for a wardrobe?

 

[rogxwhit]

And maybe to save depth, instead of housing the back panel in a slot, plant it onto the back edges of the carcase - but use glue as well as pins / screws to stop it being pushed off in use.

 

[NathanJT]

You could use a 6mm backing panel especially if it could have an intermediate fixing (or two) eg to a fixed shelf to stop it being too 'flappy'. It would function for anti-racking as well as anything thicker.

Why MR for a wardrobe?

MR mainly because I'd read in many places that it's structurally better, ie less "fluffy" when cut. I don't mind the additional cost in this instance.

 

[NathanJT]

And maybe to save depth, instead of housing the back panel in a slot, plant it onto the back edges of the carcase - but use glue as well as pins / screws to stop it being pushed off in use.

Yeah, it's my intention to add it to the rear face of the frame rather than slotting it in, using glue and screws to fix in place.

It's only the single large carcass that won't have a second cross member half way down as that'll be for full height hanging. I suppose I could easily add a brace at the back though to support it.

 

[rogxwhit]

If it'll be touching the back wall there won't be much of a problem ...

 

[Distinterior]

Not really sure why you would want to use MDF as a cabinet material...? What are you planning on finishing / sealing it all with...? Paint?
You could just use 18mm MFC which is pre finished, available in hundreds of colours and use matching 8mm material for the backs.

 

[seanf]

You will also need to leave some amount of space behind the carcass or you risk mould forming between it and the wall. An open back like you have now will prevent this

Sean

 

[rogxwhit]

Good point - is it an outside wall?

 

[Distinterior]

I rebate my 8mm backs so there is a 20mm void behind on the wardrobes that I make.....

Here's a couple of scrap bits to show how I do it...

 

[NathanJT]

It will be touching the back wall but It's an inside wall thankfully. How likely is mould in that scenario?

 

[NathanJT]

What if, instead of fully sealed backs, I simply braced the carcasses in several points? That would be a similar solution to what we have now, but with the vertical divides needed for shelves/drawers.

 

[NathanJT]

I rebate my 8mm backs so there is a 20mm void behind on the wardrobes that I make.....View attachment 143143View attachment 143144

Here's a couple of scrap bits to show how I do it...

It's certainly an option but I only have 570mm in total for the depth of the wardrobe. Dropping 20mm off that would make the hanging space a bit cramped, no?

Although that space would also help me with the wiring for the interior lighting.

 

[MARK.B.]

If fitting into alcoves do you really need 80mm spacers on the sides ?

 

[NathanJT]

If fitting into alcoves do you really need 80mm spacers on the sides ?

It's primarily to give some uniformity to the carcasses. I'll have 3x900mm wide and one 450mm wide. Thereby all the doors will be a uniform width. Yes, I suppose I could stretch everything laterally to fill the entire space but I wanted to ensure I have some leeway for out of true walls AND more importantly, for my beginner needs, fairly simplistic measurements, ie multiples of 450mm.

There's also an additional reason. One end of the alcove actually buts up to a door frame. So that additional space on the side means the wardrobe door is inset from the corner slightly, meaning the doors don't clash quite as badly as they might. This is how the current built ins are, and to be honest I think it's worth keeping.