The under stairs drawers I make are suspended on heavy duty steel runners, usually the telescopic, ballbearing guided sort. This means that there is no wear on the floor in front of the drawers. There are all kinds of different runner available and a great variety of cost and specification but experience has led me to prefer two of the Accuride range with maximum load capacities of approximately 220 kg and 160 kg. This may seem excessive but it is important to bear in mind that the weight of the drawer itself can be substantial and the more spare capacity a runner has the longer its lifespan. For example, the 220 kg runners have been tested to 10,000 cycles (opening and closing) at full load but 75,000 cycles when carrying 180 kg. That’s equivalent to opening and shutting the drawer 20 times every day for ten years.
I use a mixture of different materials for making the units. My preference for any load bearing parts of the supporting structure is birch plywood due to its strength, and this is one aspect of the design I won’t compromise. Other component materials can be chosen to suit a given budget but for the drawers themselves I like to use poplar plywood where possible because this is far lighter than both birch plywood and MDF (a cheaper alternative). Poplar is relatively easy to dent though so surfaces within the drawers that might be subject to wear (i.e. shelves) I will either cover with a protective layer of cork or make from MDF, which has good surface hardness.
Any partitions will be constructed from pine which I take the trouble to plane myself to make sure it is flat and square and clad with moisture resistant MDF. Drawer fronts and cupboard doors will generally be made with moisture resistant MDF and are usually supplied primed and ready for top coating. Tongue and groove style MDF is a popular choice for the drawer fronts, though other decorative details are possible, as is a plain, flush front.