lavo lavare or lavere lavi lautum or lotum or lavatum, to wash, bathe; to moisten, wet; to wash away. Hence partic. lautus -a -um, washed; hence fine, elegant, sumptuous, refined; adv. laute.

I'm not sure what the gerundive of "lavare" would be, but if it were something like "?lavandum?" meaning "to be washed" it might be what you want.