No. 03 · Lath and plaster
Plaster repair. Old walls, made sound again.
Cracked, bulging and loose plaster in older houses, reattached to its lath, bridged and rebuilt, then finished to match the wall around it, so the house keeps the solid, quiet walls it was built with.
About plaster repair
Until the 1930s or ’40s, nearly every house was finished in plaster, and much of what survives is in better shape than it looks. Three-coat plaster is hard and dense; it resists fire and keeps sound from carrying between rooms.
It fails in familiar ways. A roof, a gutter or a pipe lets water in. The house settles and diagonal cracks run from the corners of doors. Or the keys, the plaster that squeezed through the lath and holds the wall on, break, and a ceiling begins to sag.
Most of it can be repaired without tearing out the room. Loose plaster is drawn back to the lath, cracks are bridged, holes are rebuilt, and each repair is finished to the surface around it.
Old walls hide things, and Randy explains what he finds as he goes: “It’s not a grab and run situation here… we will educate you during the entire process.”
When it’s called for
When plaster needs attention
Cracks that keep returning
Cracks that reopen every year as wood lath swells and shrinks with the humidity, or that run diagonally from the corners of doors and windows.
Bulges, sags and soft spots
Plaster that gives when pressed, or a ceiling that dips, has usually lost its keys. It should be reattached before it lets go.
Water stains and crumbling
Plaster a leak has softened or stained. The leak is fixed and the wall dried first; a repair over a wet base will fail again.
Holes from past work
Openings left by a plumber, an electrician or a removed fixture, patched poorly or not at all.
A finish coat lifting
The thin top coat flaking away from the base coat beneath it, in shallow, irregular patches.
How a plaster wall holds on
Plaster in older houses goes on over lath: narrow wood strips with gaps between them, or, later, metal mesh or gypsum lath. The first coat is pushed through the gaps and slumps over the back of each strip. Those lumps are the keys, and they hold the wall up.
Good work on wood lath was three coats: a scratch coat, a brown coat to build thickness, and a thin, hard finish coat. By the late 1930s, new houses were plastered almost entirely over gypsum lath, which needed only two.
When the keys break, from water, settling or age, the plaster parts from the lath. That is why a bulge matters more than a crack: a hairline crack in sound plaster is cosmetic, a loose ceiling is not.
The work
How the work goes
Find the cause
Every repair starts with why the plaster failed: a leak, a settling corner, a ceiling carrying too much. Randy walks the rooms with you, and the walkthrough and written estimate are complimentary.
Reattach what’s loose
Plaster that has lost its keys but is otherwise sound can be drawn back to the lath with screws and broad plaster washers. It doesn’t have to come down.
Bridge the cracks
Cracks are opened slightly, bridged with fiberglass mesh tape and filled with setting-type compound, which hardens by chemical reaction and shrinks less than ordinary joint compound. A finer compound goes on last, because setting compound is hard to sand.
Rebuild what’s missing
Where plaster is gone down to the lath, the old edges get a bonding agent and the hole is built back up in layers, each stepped over the last. Larger openings can take a piece of board shimmed to the plaster’s thickness instead.
Finish to the wall around it
The repair is feathered into the old surface, or the whole wall is skimmed so old and new read as one. On a wavy old wall, the patch follows the wall’s contour; a dead-flat patch would stand out.
From the job sites
“Randy and his guys painted the interior of our new home, and did a great job! We needed our entire main floor and some of our upstairs rooms repainted…”
Questions
Asked at the walkthrough.
How do you fix damaged plaster?
It depends on the damage. Hairline cracks are taped and filled; loose plaster is reattached to the lath with screws and plaster washers; holes are rebuilt in layers or patched with board shimmed to the wall’s thickness; and any leak is fixed first. The aim is to keep as much sound plaster as possible.
Why is plaster no longer used?
Drywall took over in the mid-twentieth century because it went up faster, with less skilled labor and no long wait for plaster to dry; gypsum plaster takes two to three weeks to dry fully. Plaster is still made, and old plaster walls are worth keeping: they are harder and denser than drywall, and they damp sound between rooms.
How do you match up drywall with plaster?
Plaster on wood lath is usually thicker than standard drywall, so new board is shimmed or layered until it sits just below the plaster face. The joint is taped and filled with setting-type compound and feathered wide, and the area is skimmed so plaster and board take paint the same way.
Is it better to repair plaster or replace it with drywall?
Where the plaster is sound and attached, repair usually is: the wall keeps its weight and sound control, and the trim around windows and doors keeps its original depth. Replacement makes sense where long-term water has ruined the plaster or large areas have come away from the lath. The walkthrough settles which, and the cost depends on the room.
Can loose plaster be saved?
Often. If the plaster around it is sound, a loose section can be pulled back to the lath with screws and plaster washers. The washers and any cracks are then taped and skimmed over, so nothing shows once it’s painted.
Do cracks in plaster mean a structural problem?
Usually not. Hairline and seasonal cracks are cosmetic. Diagonal cracks that keep widening, especially from the corners of doors and windows, can point to settling or an overloaded frame, and should be seen by a structural engineer before they are patched.
Where
Plaster repair, town by town.
Randy works from Easton across the Lehigh Valley and Bucks County. Choose your town for what plaster repair involves in its houses.
Lehigh Valley
Related
Often done together.
Consultation
Request a private consultation.
Private walkthrough & written estimate, complimentary. Tell us a little about the house and the rooms, and Randy will be in touch to arrange a time.
- Hours
- Monday – Friday8:30 AM – 5:30 PMSaturday10 AM – 3 PMSundayClosed
- Service area
- Easton, Bethlehem, Allentown and the greater Lehigh Valley; Bucks County, Pennsylvania.
Fully insured — proof on request. Residential and commercial.