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Construction Formulas

Span, load, coverage and installation equations.

Floor Span Calculator

Floor Span Calculator
Line load w = Total load (kN/m2) x Spacing (m)
Floor Span Calculator
Second moment of area I = b x d^3 / 12
Floor Span Calculator
Deflection (UDL) = 5 w L^4 / (384 E I)
Floor Span Calculator
Bending moment M = w L^2 / 8, stress = M / Z (Z = b d^2/6)
Floor Span Calculator
Pass if deflection <= L/300 AND stress <= grade strength

Flooring Coverage Calculator

Flooring Coverage Calculator
Floor area = (Room length x Room width) in m2
Flooring Coverage Calculator
Area needed = Floor area x (1 + waste%)
Flooring Coverage Calculator
Plank area = Plank length x Plank width
Flooring Coverage Calculator
Planks = ceil(Area needed / Plank area)
Flooring Coverage Calculator
Packs = ceil(Area needed / Pack coverage)

Sanding Sequence Planner

Progress through grits
80 -> 120 -> 150 -> 180 -> 220 ...
Sanding Sequence Planner
Never jump more than ~one grade (avoid over ~1.7x increase)
Sanding Sequence Planner
Each grit removes the scratches of the previous grit
Sanding Sequence Planner
Always sand with the grain, not across it
Sanding Sequence Planner
Remove all dust between grits to avoid stray coarse scratches

Timber Post Calculator

Timber Post Calculator
Effective length Le = K x Height (K by end condition)
Timber Post Calculator
Slenderness = Le / radius of gyration (r = sqrt(I/A))
Timber Post Calculator
Compression (squash) capacity = fc x Area
Timber Post Calculator
Euler buckling load Pcr = pi squared x E x I / Le squared
Timber Post Calculator
Safe if capacity >= load AND slenderness <= 180

Wind Load Calculator

Wind Load Calculator
Dynamic pressure q = 0.613 x V squared (V in m/s, q in Pa)
Wind Load Calculator
Design pressure = q x Terrain factor x Height factor
Wind Load Calculator
Height factor = (Height / 10) ^ 0.14 (above 10m)
Wind Load Calculator
Wind force = Design pressure x Area x Force coefficient
Wind Load Calculator
1 kN ~ 102 kgf (divide Newtons by 9.81)

Glue Consumption Tool

Glue Consumption Tool
Total bond area = Area per joint x Number of joints/faces
Glue Consumption Tool
Glue (grams) = Total area x Spread rate x (1 + waste%)
Glue Consumption Tool
Kilograms = Grams / 1000
Glue Consumption Tool
Packs = ceil(Kilograms / Pack size)
Typical spreads
PVA 150-250, PUR 120-180, epoxy 200-400 g/m2

Stair Geometry Tool

Stair Geometry Tool
Number of risers = round(Total rise / Target riser)
Stair Geometry Tool
Actual riser = Total rise / Number of risers (all equal)
Stair Geometry Tool
Number of treads = Risers - 1
Blondel formula
2 x Riser + Going = 550-700 mm
Stair Geometry Tool
Pitch angle = arctan(Riser / Going), keep under ~42 deg

Coating Drying Calculator

Coating Drying Calculator
Temperature factor = 2 ^ ((25 - Temp) / 10)
Coating Drying Calculator
(drying roughly halves per +10C, doubles per -10C)
Coating Drying Calculator
Humidity factor = 1 + (RH - 50) / 100
Coating Drying Calculator
Adjusted time = Base time x Temp factor x Humidity factor
Coating Drying Calculator
Project time = (Coats - 1) x Recoat + Full cure