How to repair water damage in the kitchen caused by a dishwasher?

If it dry and there is no visible damage you don't need to worry too much. If it has degraded the chipboard slightly you might want to replace it. A sensible step to take is to treat it with wood hardener available at most DIY stores. Just pour it on in a generous manner. Too thin and it won't penetrate deeply just create an impermeable barrier. There might be better wood rot treatments out there for deeper treatment if you want to undertake your own research? For future reference there are washing machine and dishwasher 'trays' available. They go under the appliance and any leaking water travels to the front where it is visible. They don't capture and store leak water as such but prevent damage from long term insidious leaking. Hope that helps. Sinclair

You need to identify the cause of the leak for starters. Once you have determined and stopped the leak then remove the washer from its position and fully assess the amount of water damage to the surrounding cupboards and floor boards. If it is a new leak it is possible to dry the wood out and not have to replace it. It would be a good idea to apply a seal to the wood once dried. If the wood is too damaged then replacement of the affected areas will be necessary. Placing a plastic overflow or drip tray underneath the machine is also a good idea to catch any leaks in the future. This tray should be slight tilted towards the front so that all water will flow forward and can be dried up. If the machine is leaking from parts other than the inlet water supply, it may require replacing or servicing.