The wall is damp where the new fireplace is being installed.

Sometimes the situation arises where you want to put an open fire or a freestanding stove against a damp wall. On other parts of the wall or around the whole room you may have or plan to have a damp proof membrane. One of the most popular suppliers is Newton Waterproofing and systems called ‘Newtonite’ or ‘Newton System 500’ are very common. Newton Waterproofing do not recommend using their membranes in the reveal of a fireplace. They have cementitious sealers such as 107F or Whatstop 110 instead in this situation. We recommend preparing and sealing the wall with one of these products and then to proceed as normal (with fireplace render, a fire back or firebricks etc).