What undercoat should I use before multi finish to prevent future damp on a internal wall?

damp has many causes and remedies. it depends on a number of factors regarding the age of the house what the fabric of the building was built with, where the damp is situated and whether it is a solid wall or chimney place etc. usually there are underlying factors that attribute to damp in houses such as broken drains, bridging of the cavity, high ground levels, leaking gutters, blocked air bricks, wall tie corrosion, external renders used inappropriately, thermal bridging and salt build up in walls, plus many more. so you see it isn't as easy as it first sounds, what you need is a competent person who is also honest(yes there are still a lot of builders who are honest) to investigate the problem for you. usually the problem can be rectified without the need for expensive chemical injection systems, so ensure you talk through the possible causes and remedies available to suit your particular damp issue as using a gypsum based product could exacerbate the problem depending on the age and makeup of the building.

Hi Sam 1) was the damp issue rising damp or penetrating damp? eg was the damp from a leak from above or the side or is it a problem with the DPC or in a basement. If the problem is with the DPC then if you have just plasterboarded over it you will continue to have damp problems unless you fix with a correct method. 2) multi finish is a type of plaster you could use either multifinish or board finish on a plasterboard the plaster then paint when totally dry.

Hi the damp issue must be fixed before plastering,if fixed should be ok with any backing or board when dried out,might be good idea to spray area with anti fugal spray an wash down.