While doing some bathroom renovation, I noted foam insulation around the edge of the recessed bath when examining underneath it. The foam would extrude in places above and below the edge of the bath where it meets the wall as if it was used to fill the gap between the bath and the wall.
The foam is of the same polyurethane spray type that is used for thermal insulation in construction and is brown in color with a slightly crunchy, pliable consistency.
The bathroom has not been renovated since construction, so presumably the foam was deemed to have some purpose by the construction workers. But what could that possibly be?
Thermal insulation? If so, why just at the edge of the bath? Could it be for waterproofing?