Thompsons One Coat Damp Seal is a high performance interior seal developed to form a breathable, obliterating membrane that seals & permanently stops the reappearance of damp, water & other household stains. Suitable for application to both dry & damp walls & ceilings the micro-porous formulation allows trapped moisture to evaporate to prevent paint flaking or wallpaper peeling off. Full coverage can be achieved in just one coat, ensuring the surface is prepared for decoration in as little as 4 hours. 250ml