Lath and Plaster vs Drywall: Repair or Replace?

If your house went up before the 1950s, there is a decent chance the walls are not drywall at all. They are plaster, troweled wet over strips of wood lath or an early gypsum board. We run into these walls in the older neighborhoods around downtown St. George and in Cedar City, and the first question owners ask is always the same: fix it or tear it out?

First, confirm what you have. Knock on the wall: plaster sounds dense and dead, drywall sounds hollow. Push a thumbtack in; it slides into drywall easily and fights you in plaster. The surest check is to pull a switch plate and look at the edge of the opening. Plaster shows as a thick, layered sandwich, often close to an inch, where drywall is a uniform half inch or five eighths with paper faces.

Old plaster is a genuinely good wall. It is harder than drywall, it deadens sound better because of its mass, and a full plaster system carries real fire resistance. Those walls have already stood for seventy or more years. None of that should be thrown away casually.

The failures you see are usually specific and diagnosable. Hairline cracks come from seasonal movement and are cosmetic. Wider diagonal cracks radiating off door and window corners suggest the house has settled, which is common in older Southern Utah foundations. The serious one is delamination: the plaster has broken its grip on the lath behind it.

Test for delamination by pressing gently on the wall near a crack. Solid plaster does not move. If the surface flexes or you feel a soft crunch, the keys, the little hooks of plaster that squeezed through the lath gaps, have broken off, and the wall is hanging on friction. A ceiling doing this is a safety issue and moves to the front of the line.

Loose plaster does not always mean demolition. Plaster washers, which are thin perforated discs screwed through the plaster into the lath or framing, can pull a drummy section tight again. We then tape and coat over the repair. For a wall that is structurally fine but ugly, a skim coat is often the answer.

Skim-coating means troweling thin coats of finishing compound over the entire surface to build a new, flat face. It preserves the mass and sound-deadening of the original wall, keeps trim and jambs where they are, and avoids a gut-level mess. It is our default recommendation when the plaster is at least ninety percent well-attached.

Matching original plaster texture is its own craft. Many older homes here have a subtle troweled or sand-float finish that modern spray textures get wrong, and a mismatched patch reads instantly. We match by hand with the same tools that made the original: trowel, float, and a compound mix adjusted until a sample patch disappears. Anyone quoting plaster repair should be able to show you a blended patch they are proud of.

So when does replacement with drywall win? When more than a third of the wall is loose, when water damage has rotted the lath, or when the walls are coming open anyway for rewiring, replumbing, or insulation. Old houses in Washington County often have empty stud bays, and if you are ever going to insulate, doing it while the wall is open makes the demolition earn double.

Be honest about the tradeoffs of replacement. Half-inch drywall is lighter and thinner than the plaster it replaces, so it transmits more sound unless you compensate, and every jamb and casing was set for the thicker wall. We deal with that by using five-eighths board or furring, but it is fitting work that a quick bid can miss. Demolition of plaster is also brutally dusty, and homes of a certain age need a lead paint check before anyone starts breaking surfaces.

Cost follows scope on these jobs. A washer-and-patch repair is a day or two of work, a whole-room skim coat sits in the middle, and full demolition and rehang costs the most because you are paying for tear-out, disposal, and finish carpentry adjustments on top of the drywall itself. The right way to decide is a walkthrough, not a guess over the phone.

Our crews hang and finish drywall every week, and we also patch and skim plaster in older homes across St. George and Cedar City. That means we have no reason to push you toward tear-out when a repair will hold. If you are staring at a cracked plaster wall and do not know which side of the line it falls on, have someone qualified put hands on it before you decide.