It isn’t as old as plaster, but drywall has a surprisingly long history, with early forms dating back to the late 19th century. Known variously as plasterboard, gypsum board, Sheetrock (a trade name), rock, or wallboard, drywall is a uniform panel of gypsum plaster pressed between thick sheets of paper. Old work can be replicated, but that’s another story. Ornaments including ceiling medallions are cast in a mold, then applied. Mouldings, however, are run in place, the profile created by pushing a template against wet plaster. This article concerns itself with three-coat plaster, applied to wood or metal lath and troweled smooth. The result is a superior, handmade wall surface that offers surprisingly good insulation and sound-proofing qualities. Once the brown coat has cured, the top or finish coat goes on, either smooth or in a variety of textured finishes. The Brown CoatĪs the brown coat goes on, the plasterer levels out wall surfaces and creates square and plumb corners. The top surface of this scratch coat is then scored to prepare it to receive the second or brown coat. The plasterer forces the wet mixture thickly through gaps in the lath to form “keys” that harden and lock the coat in place as it cures. Three coats of wet plaster are applied in layers to the lath: the scratch coat, the brown coat, and the finish coat. Illustration by Rob Leanna based on Kathy Bray What is a 3-Coat Plaster System?Ī traditional multi-coat plaster system begins with a substructure of lath-thin wood slats or metal mesh-that’s attached to the wall framing. Three-coat plaster is a system of multiple layers that work together to form a strong, sound-dampening, fire-resistant wall. About 150 years ago, a new component, gypsum, was added to the sand and lime mixture to enable the plaster to cure more quickly and allow for faster working times. Historically, plaster consists of dry components including sand, lime, and cattle hair (or straw or manure) mixed with water to create a wet, plastic medium that cures and hardens as it dries. More serious repair problems include delamination, bulging walls, and key failure, where plaster has broken loose from its grip on the lath substructure.Īpplied with craft and skill, interior plaster is a near-magical building material for creating and coating walls and ceilings. The most common type of damage to plaster is cracking, progressing from the superficial and easily repaired to deeper and wider cracks that require multiple repair techniques. It’s much easier to repair cracks or patch holes with this versatile material than with drywall. In many cases, problems with plaster can be fixed. If sections or entire walls need attention, don’t let the idea of working with old plaster intimidate you. Thanks for that Apart from a box room and a wee bathroom adding some inches to the exterior walls shouldn't be a problem in most rooms, though as you say it will be a lot of work: there will be a fair bit of stuff like cornices, architraves & fire surrounds to replace/move.Many houses built before about 1950 retain at least some of their original plaster walls. If rooms are big enough you don,t even need to rip out old plaster +lathes-just build a modern house inside it inside it ?Īpply vapour barrier to the frames before you lift them up into place and you got full damp proofing at same time and a gap for the old walls to breath into the roof spaceĪ house that old will be built with a cold roof and lots of drafts in the loft area -so you kill all problems at same timeĪlso will be a job you can do while still living in it ,a bit at a time if you wishįilling the gap with anything will stop the air flow to the roof you must have with this type of old house -you will make more damp problems Maybe a bigger job then you wanted but is the right way to go long term and also a chance to replace electrics etc at same time and have house with modern insulation stds Maybe time to think about getting rid of the lathe and plaster and build stud walls -providing rooms are not very small
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