Later details were formed using fibrous plasterwork. Where decorative plasterwork, such as cornicing, is damaged repairs can usually be undertaken by a skilled plasterer.Įarly plasterwork was ‘run’ in situ using a template and running it around the top of the wall over wet plaster to create the profile of the cornice. This in turn is scratched and then a thin ‘setting’ or ‘skimming coat’ is used to create a smooth surface. Often referred to as a ‘scratch’ coat, the first plaster coat creates a reasonably flat surface and is ‘scratched’ in a diamond pattern to provide a key for the next coat.įor good-quality work, a ‘floating coat’ or a ‘straightening coat’ is applied next and is worked until perfectly level.
If these continue to come to the surface, plaster may have to be stripped. Where damp is present, salts may pose a problem. Unlike modern plasters, lime plasters that have become wet generally dry out with their integrity intact so need not be removed. Use a steam stripper to remove stubborn coatings, being careful not to allow steam to penetrate the plaster.Apply warm water or proprietary wallpaper stripper with a sponge or brush.Gently use a scraper but avoid scoring through the surface into the plaster.Always undertake a test first on a small unobtrusive area.When removing, proceed with care and be aware that wallpaper may be acting as a support to defective plaster underneath. Wallpapers, paints and other finishes can spoil the appearance of plaster surfaces and may trap moisture. Where the bond with laths has failed, reinforce by pouring fresh plaster from above and strengthening with a jute scrim set into this and secured to the joists.Always use screws for any fixings to avoid vibrations to fragile ceilings.Investigate from above if access is available from a loft or by carefully lifting floorboards.Problems with ceilings frequently result from the plaster bond having failed, structural movement, failure of joists, damp problems and rotten or beetle-infested laths. Removing a loose section of old lime plaster Mending sagging or cracked ceilings Alternatively, gypsum may sometimes be added to a lime plaster mix for the same purpose. To patch repair plasterwork, slightly treat the exposed edges of the existing plaster with water or diluted PVA (one part to 10 of water) to control suction and prevent cracking.Cracks and pockmarks may be filled using matching plaster, or narrow ones with proprietary interior filler gauged with whiting.
Make necessary repairs with appropriate traditional materials.Consult a structural engineer if in any doubt.Monitor cracks over a period of time by marking and dating their end point on the wall.Investigate bulges or anything larger than a hairline crack.Rake out thin cracks and fill with a good filler.Some cracks and bulges in plaster may be superficial or localised others result from failure of the masonry or timber beneath, or may indicate wider structural problems within the building.
Inappropriate modern plasters and finishes.DIY: Make plastering walls an easy job with our guide.Rotten laths can result in plaster sagging or bowing. In the case of stud walls and ceilings, timber laths are fixed between the studs or joists and the plaster is pushed through the gaps between the laths.