Abstract: A showerbath base plate having an annular gutter in the form of a ring according to the contour of the showerbath is disclosed. The gutter has an inclined bottom the lowest portion of which is connected to a drainage conduit. Inner and outer walls of the gutter have at their respective upper edges flanges extending horizontally away from the gutter. A flat sheet is supported on the inner wall flanges with an elastic joint therebetween. The flat sheet extends over the gutter to near the flanges of the outer gutter walls with an aperture between the flat sheet and the outer wall flanges.