Resting a bookcase on kitchen cabinet plinth feet

[RookieTony]

Dear DIYNot forum members,

Is it a good idea to build a custom-made bookcase on the plinth feet shown below?

The bookcase will consist of kitchen units at the bottom of the case, then a kitchen worktop, then MDF shelving above. The base of it will look a bit like this:

In theory, if each leg can take 150 kg of weight, adding three feet on the side wall of each cabinet should support the structure... but then there is unintentional displacement of weight, aging of plastic, etc.


What would you say?

Thank you in advance!

 

[Deleted member 174758]

Dear Rookie Tony, probably not

Standard kitchen unit feet are relatively flimsy plastic - they can carry a static (vertical) load, but if you apply any sideways load (such as if the bookcase is moved to a new position by dragging it across a carpet) they are liable to break. The reason they can work with kitchen units is because kitchen units are often fixed to a wall/walls, trapped between end walls, secured to other kitchen units in runs, fixed to a worktop which is siliconed to a wall, etc - in other words they can never move. If you ever assemble a CKD kitchen you'll find out what I mean by weak - it isn't completely unknown for fitters to snap the odd leg when manoeuvring units into place, especially if the floor is a bit uneven.

Also worth bearing in mind that you are limited to something like 13 to 16mm screws to hold the feet on (they screw through into the underside of the bottom shelf) - and they can also pull out if the piece is dragged sideways at anybtinr.

A better bet is something like a softwood ladder frame with a thin MDF plinth round 3 sides

 

[RookieTony]

Hi @JobAndKnock !

Thank you for your comprehensive response.

While your reponse tells me exactly what can go wrong and how these feet usually break, it leaves me "on the fence" :
The cabinets forming the base of the bookcase are exactly as wide as the gap between two walls that they go into:
60cm + 60cm + 50cm + 60cm + 60 cm = 290cm (wall width).

The walls are a bit uneven, but we checked and the cabinets fit perfectly and can't physically move sideways. I guess this would exclude any side-to-side movement, which usually breaks the legs.
The top of the shelf would also need to me secured to adjacent walls, making the structure a 'static load'.

If my assumptions are correct, that leaves me to explore one more sort of breakdown the feet may experience: breaking from the overall load of the weight of the cabinets, their contents, the worktop, the MDF and the books themselves.

Are the feet likely to break that way?

 

[Deleted member 174758]

Are the feet likely to break that way?

If you have carpet on the floor it's always possible you'll break a foot when you push them in into position. Then you will need to level up each cabinet front to rear and end to end, starting at one end (just like when installing a run of kitchen cabinets).

My own experience of joinery makes me more likely to consider making a single ladder frame up out of softwood (2 x 2in or 3 x 2in square edged, planed), levellling that up then installing the cabinet bodies atop this levelled platform. That is much stronger, more rigid and lower than using kitchen feet (which are normally 125 to 150mm high) and if you use square edge stock can be painted out to match the rest without the need to make up a plinth cover, which plastic kitchen cabinet feet will require, because let's face it they aren't the prettiest of things

 

[RookieTony]

Thank you for your suggestion!