The existing floor level to the house may be quite high above ground, and in cases such as this it is more practicable to use timber joists, with a void underneath.
Efallai y bydd llawr presennol y tŷ yn eithaf uchel uwchlaw lefel y ddaear, ac os felly, byddai'n fwy ymarferol defnyddio distiau pren gan adael gwagle danynt.