Lath & Plaster to Drywall · Cambridge
Converting Lath and Plaster to Drywall in Cambridge
Good plaster is a better wall than drywall. The job is telling the good plaster from the failed, and replacing only what has to go without losing the trim that makes the house.
The pre-1920 houses of Galt, Preston and the older part of Hespeler were plastered over wood lath: thin strips nailed to the studs with gaps between them, and lime plaster pushed through the gaps so it curled over behind the lath and locked on. Those curls are the keys, and a plaster wall fails when they break — the plaster is still there but it is no longer attached, and it bulges, cracks in a map pattern and sounds hollow when tapped. Water from a roof or a bathroom above is the usual cause; a century of the house moving does the rest.
Repair, overlay or strip
- Repair where the plaster is sound and the problem is cracks or a small failed area. Cracks are bridged and skimmed; a loose patch can be re-anchored with plaster washers or cut back to sound material and filled. A good plaster wall is thick, hard, quiet and worth keeping, and we will say so where it is true.
- Overlay where the plaster has failed broadly but is not falling: new 9.5 mm (3/8 in) or 12.7 mm (1/2 in) board is screwed through the plaster and lath into the studs, then taped and finished. Far less mess and no exposure to what is in the wall cavity, but the wall gets thicker, so window and door jambs need extensions and the trim is removed and reset. The right answer in most rooms where nothing behind the wall needs touching.
- Strip to the studs where the plaster is coming down anyway, the room is being rewired or insulated, or the framing has to be corrected. The messiest and most expensive route and sometimes the only honest one. It exposes knob-and-tube wiring, missing insulation, old chimney breasts and framing that was never plumb, all of which get dealt with before the new board.
Test before you cut
Original lime plaster is generally not an asbestos concern. The patches, skim coats, joint compounds and textured ceilings added to these houses from roughly the 1950s through the late 1980s can be, and vermiculite found above a ceiling is treated as containing asbestos by default. A sample of any suspect layer goes to a lab before it is sanded, scraped or demolished. If it is positive, removal is a licensed abatement contractor's job under Ontario's asbestos regulation and we board afterwards. The test costs little and the alternative is not acceptable.
Trim, reveals and the shape of the room
Deep baseboards, wide casings, plinth blocks, picture rail and crown are why these houses are loved, and a plaster conversion that loses them is a loss. Trim comes off carefully, is labelled by location and stored flat. New board is scribed to the openings rather than the trim being cut to the board. Where an overlay adds thickness, jamb extensions bring the window and door frames flush so the casings sit right. Inside a heritage district or on a designated house, the window reveals are part of what the City protects, and a word with the City's heritage staff before the casings come off is a sensible step.
Framing that was never flat
Lath and plaster hid a lot. Studs in these houses are rough-sawn, irregular and often out of plane by more than drywall will forgive, so a stripped wall is strapped or shimmed to a true surface before board goes on. Ceilings sag at the centre of old rooms and are furred level. None of this shows in the finished room, and all of it is in the quote.
Frequently asked questions
Can you drywall right over the plaster?
Often, yes — an overlay screwed through to the studs is the least disruptive conversion. It adds thickness, so the trim is reset and jambs extended, and it is only right where nothing behind the wall needs attention. Where the room is being rewired or insulated, stripping makes more sense.
Will my baseboards and casings survive?
That is the aim and usually the result. Old trim is removed carefully, labelled and stored, then reinstalled. Occasionally a piece is too brittle or was damaged long ago, and a matching piece is milled; we tell you before, not after.
How messy is stripping plaster?
Very. Lath and plaster demolition fills a room with fine dust and a large volume of debris, so the room is emptied, sealed and the HVAC covered, and disposal is planned — plaster is not drywall and goes as a separate load. It is why overlay is chosen where it can be.
Serving Cambridge and surrounding areas. Contact us for a no-obligation quote specific to your property.