Understand it.
Then rebuild it.

From dimensions to weight

1. Convert the lengths first

For area, square the conversion factor: 1 in² = 0.00064516 m². A 3-inch built-up front edge is not a 3-inch slab thickness. Use the actual material thickness.

2. Calculate the outside area

For a rectangle, A = L × D. Split an L-shaped outline into non-overlapping rectangles and add them. For a notch, subtract the missing rectangle once. Use dimensions from the drawing, not proportions measured from a photograph.

A confirmed rectangular opening has area length × depth; a circular opening has area πr². A rounded rectangle has area LD − (4 − π)r² when all four corners share radius r. These formulas calculate area only: placement, edge clearances and separation still need a CAD/template check. The fixed project tables currently keep openings in the gross area.

3. Give it thickness

Check the units: m² × m gives m³. Apply quantity only after finding one piece’s result, and keep different thicknesses separate.

4. Apply density, then gravity

The 2400 kg/m³ density is an estimate, not a test of the Project 2 slab. Kilograms describe mass; newtons describe force. Changing gravity changes weight, not mass. Fixed drawing/support pages use g = 9.81 m/s². The interactive tools use standard gravity 9.80665 m/s²; that produces about 0.034% less force for the same mass.

5. Check whether the result makes sense

For unchanged area and density, a 30 mm slab has 1.5 times the mass of a 20 mm slab. Three identical copies have three times the volume and mass. Keep full precision until the final display; extra decimal places do not make a handwritten dimension or estimated density more certain.

If density has a justified range, multiply the same volume by its low and high values. For example, the historical TCE family range gives about 80.7–88.7 kg for this piece. That is a reference sensitivity comparison, not a measured uncertainty interval for the Canadian slab.

From weight to support forces

A free-body diagram isolates the stone. Draw downward loads, upward reactions and distances. In a stationary model, upward and downward forces balance, and clockwise and anticlockwise moments balance. A moment is a force multiplied by its perpendicular distance.

L is the distance between the assumed support lines. x̄ is the gross mass-centre distance from the left support, and xₚ is the added load position. For a uniform rectangular slab both are L/2 in the centred example. For a shaped uniform slab, split the outline into rectangles and use x̄ = (A₁x₁ + A₂x₂ + …) ÷ (A₁ + A₂ + …). Subtract notch areas and their moments. This uses algebra, not calculus.

The portfolio’s two-support model uses the outside length as its assumed span. That does not mean the stone is allowed to bridge that distance. The extra 500 N is an example load, not a building-code load or a seat rating.

A bracketed overhang example

The assumed bay is 400 mm wide with a 350 mm overhang. These dimensions are examples. A product’s published load rating only applies under its specified mounting conditions; a small demand-to-rating ratio does not verify the stone, wall, screws or cabinet.

A vertical panel example

The examples assume a 30 mm offset e and a stated force-pair spacing h. The opposing arrows are an equivalent force couple, not measured anchor positions or fastener forces. Base bearing, panel orientation and restraints must be confirmed. Lateral and seismic loads are not checked.

What these forces cannot tell you

Force balance calculates demand. It does not supply resistance. Stone cracking and deflection, cutout corners, adhesive peel, bracket bending, screw pull-out, cabinet strength and floor load paths require actual details and appropriate product or professional checks. An adhesive’s aluminum test strength cannot be used as a stone-joint allowable.

If average stress is discussed, σ = F/A is only an algebraic average. It cannot establish the maximum stress at a sink corner or the capacity of a real seam.

Recreate one project in Fusion or AutoCAD

Start with one readable component, such as Project 2’s L-shaped surface. Keep unresolved pieces pending. Complete this checklist once, save the evidence, then repeat for the next component.

1. Create an input sheet. Record project/source ID, drawing revision, units, lengths, actual thickness, quantity, material and where every input came from. Mark assumptions and missing values.
2. Set units to millimetres. Convert each inch measurement exactly with ×25.4. Draw a known length and measure it as an import/unit check.
3. Build the closed outside profile. In Fusion, dimension and constrain a sketch. In AutoCAD, use a closed polyline with dimensions. Split a complex outline into rectangles on paper first; check that shoulder sums close.
4. Check area independently. Compare Fusion sketch/face area or AutoCAD AREA/MASSPROP with the rectangle calculation. Explain any difference before continuing.
5. Add actual material thickness. Extrude one separate body/component per physical piece. Keep thickness, built-up edging and wall height separate. For Project 2’s retained L, use the stated 20 mm as a drawing reading pending confirmation.
6. Leave unknown openings out. Add them only after confirming the fixture template, location, corner radii and clearances. Keep gross and net model versions so the removed volume can be checked.
7. Model the assembly without double counting. Keep different materials, alternative sheets and separate jobs distinct. Define butt/mitre joints before subtracting overlaps; never join pieces because they look close on the paper.
8. Compare volume and mass. Compare CAD volume with A × t, then apply the same stated density as the hand calculation. Check quantity separately. A different CAD library density will give a different mass.
9. Add supports as a separate concept. Draw measured bearing lines, spans, overhangs and seams if available. Otherwise label the supports as assumptions. Make a simple free-body diagram and solve force and moment balance.
10. Make a dimensioned drawing. Include plan, front and side views, material/thickness basis, units, quantity, revision, missing information and your actual role. Use genuine screenshots exported from your own CAD session.
11. Save editable evidence. Keep your .f3d or .dwg, a dated PDF drawing, calculation sheet and neutral export. OBJ/STL preview meshes do not contain your sketch constraints or feature history.
12. Record one check and one revision. Note what you measured or recalculated, who reviewed it, what changed and why. Ask the fabricator to resolve the project’s pending items before relying on the design.

Use a small log: date · source/input · your action · file/version · independent check · result · next question · help received. Claim only work you can show and explain.

Four questions after doing the work

See the audit and each project’s pending information → · Download the longer project guide ↓