Plaster
A wet-applied wall and ceiling finish, measured in SF or square yards.
Quick Answer
Plaster is a wet-applied finish for walls and ceilings, made from lime, gypsum or cement with aggregate and water, and troweled over lath or masonry in one or more coats. Estimators usually measure it in square feet or square yards, and carry lath, corner beads, trim and curved or ornamental work separately.
The Full Picture
Plaster has a long history. The National Park Service's Preservation Brief 21 explains that until the end of the 19th century plasterers used lime plaster made from lime, aggregate, fiber and water, and that around 1900 gypsum became usable, with the two used together for a time. Traditional three-coat work put on a scratch coat and a brown coat, each about 3/8 in thick, and a finish coat of about 1/8 in. Modern systems include gypsum plaster over lath or board, veneer plaster, and cement plaster for exterior and wet areas.
The install variant sets the price. Base-coat plaster over metal lath or a masonry base is built up in coats, with grounds, corner beads and control or expansion joints set first. Veneer systems apply a thin plaster coat over a gypsum base, which Brief 21 describes as a thin wet plaster system used as a replacement when original plaster cannot be repaired. Exterior cement plaster is closely related to stucco, which has its own page. Curved walls, domes, cornices and ornamental runs are priced separately from flat work.
The unit is square feet or square yards, where 1 SY = 9 SF, measured from interior elevations, reflected ceiling plans, wall sections and finish schedules. Lath is carried by the same area but as its own line. Linear items include corner beads, casing beads, reveals and control joints. Openings are commonly deducted, and some estimators use the gross wall area to cover the labor of working around them, which is a pricing convention rather than a rule. Specs are in Division 09 and exterior plaster in the envelope sections.
Typical pricing mistakes are pricing plaster at a drywall finish rate, leaving out lath or the substrate preparation (hacking or bonding agents on masonry), and missing the number of coats the spec requires. Repair work in existing buildings needs a survey of what the walls actually are, since patching a historic plaster wall is not the same as a new installation.
Real Examples
Common Misconceptions
People assume: Plaster and drywall are the same finish.
Actually: Plaster is wet-applied in coats and cured, while gypsum board is a dry sheet. The NPS brief treats veneer plaster as a thin wet system, and the labor and sequence differ from board.
People assume: Every plaster wall has the same coats.
Actually: Traditional work used three coats, but modern and veneer systems use fewer, thinner coats. The specification and wall type say which one applies.
Does MeltPlan Solve This?
Partially — adjacentWall and ceiling areas to be plastered come off elevations, ceiling plans and finish schedules, and MeltPlan's takeoff service pulls those areas with AI and has US-based experienced estimators review and adjust them. Plaster system, coats, substrate prep and ornamental work stay with your estimating team.
Get wall and ceiling finish areas measured →Frequently Asked Questions
What is plaster made of?
Traditional plaster uses lime, aggregate, fiber and water, and later plasters use gypsum. Exterior and wet-area plaster often uses cement.
How is plaster measured for an estimate?
In square feet or square yards (1 SY = 9 SF) of surface, with lath, beads and trim carried separately.
What is veneer plaster?
A thin coat or coats of wet plaster applied over a gypsum base, as described in NPS Preservation Brief 21, used in new work and as a replacement where original plaster cannot be repaired.
Where is plaster specified?
In Division 09 for interior work, with elevations, ceiling plans, wall sections and finish schedules showing where it goes.