Do Your Lath and Plaster Walls Need Repairing?

Man plastering a white wall

Plaster and lath are a durable form of interior wall finishing that has been used for centuries now. Plaster is not just aesthetically pleasing but when properly applied it creates a stronger finish, which is even more hardy to dents and knocks. The modern day metal lath, or backing, used behind the plaster is also more robust and long-lasting. But as with any finish, even plaster is bound to age and wear off with time. Plaster can break away or crack along the walls because it is coated on top of lath, instead of directly to studs inside walls. Sometimes due to poor workmanship and inappropriate hand application of plaster through the spaces inside the wall, the plaster does not stay in place. Or even if excess moisture enters the plaster and lath walls, cracks are likely to appear or the plaster will separate from the framework.

Signs your plaster wall needs a repair

It is essential to take time and inspect a house and the condition of the walls regularly. Recognizing signs for necessary repairs, such as crumbling plaster along walls, cracked ceilings, and insulation levels within the walls can help homeowners stay on top of repairs and help in preserving a superior home. Here are some of the signs that you may need to think of repairing or replacing your home’s existing plaster and lath walls:


You have to check for worn down surfaces in your home. Look for surface unevenness that may require some smoothing. Check your ceiling surface texture closely at eye level for uneven bumps or ridges, which may require quick fix or an entire repair. If there is extensive plaster problem you may need to consult a professional to ensure there is no underlying problem.


It is often difficult to evaluate whether your lath and plaster ceiling needs repairing or removal, especially if it begins to show signs of sag in distinct areas. In cases of sagging, your plaster may be detaching from the lath and if you push up against it with the palm of your hand, you may feel the plaster moving up and down. Sometimes dust and debris can fall through or there may even be a ceiling collapse, so be cautious during inspection. But a sagging ceiling does not always point to detached plasterwork, as old homes often settle and ceilings can slope or sag naturally over time. You can call in a plastering expert, if you believe your plaster is outdated, especially if a ceiling falls completely and the plasterwork hangs from the laths completely unsupported.  This is a rare occurrence over the entire area, but it is quite possible for some areas to develop sagging.


When plaster comes apart from the laths, it can lead to cracks developing along walls or ceilings. Plaster is a hard and rigid which cannot expand and contract in varying temperatures like other substrates, which cause cracks to form. Cracks can either be very fine and hard to spot with the naked eye or they can be deeper that look like a spider web. This type of crack is usually the result of poor workmanship from the plasterer not using enough cement. Sometimes even leaks within your plumbing systems may produce cracks from water damage to the plaster. Cracks are often noticeable in the ceiling or above the door framing, because of the stress on structure from movement.

Smaller cracks can be temporarily fixed, by filling in cracks with patching material but it may reoccur if not properly tended to. Cracks should not be allowed to grow and become more problematic. Small cracks can be repaired using flexible fillers over the top of the crack, then sanded to a smooth finish after allowing it to dry. Larger areas of loose plastering will require re-plastering before being painted or decorated over, so it is best to rely on a professional plasterer with good technique.


Water ingress often shows up as bubbling on the plaster, when the moisture penetrates through the substrate. When the paint on top of the plaster blisters, it means that the moisture has invaded the substrate from the opposite side of a wall to get under the render. This is a common problem in the walls where it backs onto a damp area, such as a bathroom. If there is no waterproofing in the bathroom to allow the water to escape, the moisture will travel through the grout in the tiles, and the brickwork to show up on the other side, as bubbles on the plaster. When the plaster has been damaged by damp or water, the plaster needs to be stripped off the wall to above the level of the damp, and treated with liquid damp proof membrane, before being finished with a stabilizing primer.

Repair work for your lath and plaster can be time taking and costly, so it is best to keep your home maintenance up to date. Once you inspect your walls to check for signs of cracking, blistering or sagging in worn down plaster and lath, there in need for quick repair or replacement. Smaller repairs that need simple fixes may lead to bigger problems later if techniques used are improper. It may be beneficial to hire a professional contractor with knowledge about building and construction to complete any repair jobs for you.


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