Plastering calculators.Plaster, render, plasterboard, drylining, drying, thermal performance and pricing.

Areas

AreasRoom wall and ceiling area less openings

P = 2 \times (L + W)

Gypsum plaster

Gypsum plasterFinish plaster bags (skim, e.g. Thistle MultiFinish)

C_{b} = \frac{C_{r} \times t_{r}}{t}

Gypsum plasterBacking / undercoat plaster bags (Thistle BondingCoat, HardWall, DriCoat, ToughCoat)

C_{b} = \frac{C_{r} \times t_{r}}{t}

Gypsum plasterOne-coat plaster bags (e.g. Thistle Universal OneCoat)

C_{b} = \frac{C_{r} \times t_{r}}{t}

Gypsum plasterSkim mixing batch and water-to-plaster ratio

C_{b} = \frac{C_{r} \times t_{r}}{t}

Render and lime

Render and limeSand and cement render: cement bags and sand tonnes

V = \frac{A \times t}{1000} \times (1 + \frac{w}{100})

Render and limeMulti-coat render: coat thicknesses and volumes (BS EN 13914-1)

T = t_{1} + t_{2} + t_{3}

Render and limeLime plaster mix (lime putty and sand by volume)

V = \frac{A \times t}{1000} \times (1 + \frac{w}{100})

Plasterboard

PlasterboardPlasterboard sheets for an area

S_{a} = L \times B

PlasterboardPlasterboard screws per board and per m²

n_{l} = ⌊ \frac{a}{s} ⌋ + 1

PlasterboardDot and dab adhesive bags and dabs per board

N = \frac{A \times (1 + \frac{w}{100})}{C}

PlasterboardJointing tape and joint compound (taped and jointed finish)

J = \frac{A}{\frac{B}{1000}} + e_{j} \times \frac{A}{\frac{L}{1000}} + L_{i}

PlasterboardScrim tape for board joints before skimming

J = \frac{A}{\frac{B}{1000}} + e_{j} \times \frac{A}{\frac{L}{1000}} + L_{i}

Beads, coving and sundries

Beads, coving and sundriesAngle bead and stop bead lengths

L_{a} = n_{c} \times h_{c} + n_{o} \times (2 \times h_{o} + k \times w_{o})

Beads, coving and sundriesCoving lengths and cove adhesive for a room

P = 2 \times (L + W)

Beads, coving and sundriesPVA sealer / bonding agent: dilution and quantity

V_{p} = \frac{A \times n}{C}

Beads, coving and sundriesTextured coating (Artex) bags and water

N = \frac{A \times (1 + \frac{w}{100})}{C}

Drying and site conditions

Drying and site conditionsDrying time estimate before decorating

T_{b} = t \cdot r

Drying and site conditionsDew point from air temperature and relative humidity (Magnus formula)

γ = \ln (\frac{RH}{100}) + \frac{17.625 T}{243.04 + T}

Drying and site conditionsSurface condensation risk (surface temperature against dew point)

γ = \ln (\frac{RH}{100}) + \frac{17.625 T}{243.04 + T}

Drying and site conditionsMinimum application temperature check

T_{low} = \min (T_{a}, T_{s}, T_{n})

Thermal performance

Thermal performanceU-value of a wall lined with insulated plasterboard (BS EN ISO 6946)

R = R_{si} + \frac{d_{1}}{1000 λ_{1}} + \frac{d_{2}}{1000 λ_{2}} + R_{g} + \frac{d_{3}}{1000 λ_{3}} + \frac{d_{4}}{1000 λ_{4}} + R_{se}

Thermal performanceThermal resistance of a plaster or board layer

R = \frac{d}{1000 λ}

Loads and tolerances

Loads and tolerancesCeiling board and plaster weight, and load per fixing

w = w_{b} + w_{s}

Loads and tolerancesFlatness check against a straightedge tolerance

u = \frac{d_{m}}{d_{a}} \times 100

Render movement

Render movementRender movement joint layout along an elevation

n = \max (\frac{L}{s}, \frac{L}{2 e_{d}})

Render movementThermal movement of a render panel (ΔL = α · L · ΔT)

Δ L = α \times 10^{- 6} \times L \times 1000 \times Δ T

Materials and coverage

Materials and coverageBags of plaster for an area at any thickness (from published coverage)

n = \frac{A t}{A_{0} t_{0}} \times (1 + \frac{w}{100})

Materials and coverageAverage thickness achieved from bags used (thickness = volume / area)

V = n_{b} A_{0} t_{0}

Materials and coverageBag weight to yield volume and coverage (V = m / ρ)

V = \frac{1000 m}{ρ}

Materials and coveragePVA or primer dilution by ratio

P = \frac{V p_{p}}{p_{w} + p_{p}}

Running the business

Running the businessAccess tower or scaffold hire cost against buying

C = W \cdot r_{w} + d_{c}

Running the businessJob price from m² rate, materials markup and VAT

N = A r + M_{c} (1 + \frac{μ}{100})

Running the businessVAT registration threshold headroom

H = T_{h} - T_{12}

Running the businessDay rate to m² rate

r = \frac{D}{P_{d}}

Running the businessLabour time from area and productivity

T_{w} = \frac{A}{P_{d} n} + T_{s}

Running the businessMarkup and margin

P_{r} = c (1 + \frac{μ}{100})

Running the businessHMRC simplified mileage allowance (cars and vans)

M = \frac{r_{1}}{100} \times \min (B, B_{1}) + \frac{r_{2}}{100} \times \max (B - B_{1}, 0)

Running the businessCIS deduction on a subcontractor invoice

B_{n} = G - V_{t} - M_{t}

Partitions

PartitionsMetal stud partition: studs, floor and ceiling channel, fixings and boards

N_{s} = ⌈ \frac{L \times 1000}{s} ⌉ + 1

PartitionsTimber stud partition: studs, plates and noggings

N_{s} = ⌈ \frac{L \times 1000}{s} ⌉ + 1

PartitionsPartition height against the manufacturer's maximum height

M = H_{max} - H

PartitionsDeflection head allowance under a slab

δ = \frac{L \times 1000}{k}

PartitionsAcoustic insulation roll or slab for partition cavities

A = (L H - A_{o}) c k

Ceilings

CeilingsMF suspended ceiling grid: primary channel, ceiling section, hangers and perimeter

n_{7} = ⌈ \frac{W \times 1000}{s_{7}} ⌉

CeilingsCeiling boards across the joists: supports per board, end and field screws

n_{s} = ⌊ \frac{L_{b}}{s} ⌋ + 1

Acoustics

AcousticsMass law sound reduction of a single leaf

R = 20 \log (m f) - K

AcousticsImprovement from adding a board layer (mass law)

Δ R = 20 \log (\frac{m_{1} + m_{2}}{m_{1}})

Fire

FireFire-rated build-up: boards, partition thickness and screw lengths

T = d + 2 n t

Weights and handling

Weights and handlingPlasterboard sheet weight and total load

W_{s} = \frac{q W_{b} L_{b}}{1000000}

Weights and handlingSheets of plasterboard a van can carry by payload

W_{s} = \frac{q W_{b} L_{b}}{1000000}

Wall linings

Wall liningsWall lining depth and floor area lost: dot and dab against GypLyner

T_{d} = c_{d} + t

Wall liningsGypLyner wall lining frame: GL1 channels, brackets and GL8 track

N_{1} = ⌈ \frac{L \times 1000}{s} ⌉ + 1

Plastering calculators.Plaster, render, plasterboard, drylining, drying, thermal performance and pricing.

Areas

Gypsum plaster

Render and lime

Plasterboard

Beads, coving and sundries

Drying and site conditions

Thermal performance

Loads and tolerances

Render movement

Materials and coverage

Running the business

Partitions

Ceilings

Acoustics

Fire

Weights and handling

Wall linings

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