All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Yes, it is permissible for them to do that, and this makes it a place that is not prepared for relieving oneself [toilet] customarily, and it is not an obligation to remove the closet [the base] completely; rather, it is enough to nail the wood down onto the ground so that it does not appear as a place for relieving oneself [toilet].
Ibn Taymiyyah said:
“The saying of the Prophet in the hadeeth reported by Abu Sa’eed, 'The whole earth is a mosque with the exception of the cemetery and the toilet;' it seems – and Allaah knows best – that he excluded what is designed in a specific shape that can only be used for those purposes; as the cemetery and the toilet have a particular shape that is different from all the rest of the land ... because the toilet is a name for a construction of a specific shape that is only used for the purpose for which it was built, and if we want to use it for other purposes, then we have to change its shape.”
Allaah knows best.