Closing a measured survey dimension chain at 1:50
An existing two-storey stone house in Lefkara is being measured for a renovation drawing set. The ground floor has three rooms in a row. Internal clear widths are recorded as 3.42 m, 3.38 m and 3.45 m, and the overall external width is taped at 11.28 m. Wall thicknesses vary from 0.55 m to 0.62 m because of rubble construction. When the draughtsperson chains the three internal widths and four wall thicknesses along the front, the total is 11.34 m - 60 mm more than the external tape. The plan is to be drawn at 1:50 and issued to a contractor for pricing. The client wants the original stone faces retained and new partitions built in lightweight blockwork. The office template uses a 0.18 mm thin line and a 0.50 mm heavy line.
1. The dimension chain does not close by 60 mm. Explain step by step how you would establish a reliable set of dimensions for the 1:50 renovation plan, and state what you would write on the drawing so the contractor is not misled.
Read the worked answer
First treat the 60 mm as a survey problem, not a drawing problem. Re-measure overall diagonals and the overall external rectangle, because a single taped width can be wrong while the diagonals reveal skew. Then record each wall separately at several heights, and separate structural stone faces from plaster and finishes. Do not average wall thicknesses: a rubble wall genuinely varies.
Build the drawing on a control rectangle taken from the most reliable overall dimensions, then fit internal partitions to it. Distribute the 60 mm into non-critical partition positions or into the plaster zone, never into the retained stone faces. Show overall dimensions and running dimensions to structural faces, and add a room-size schedule marked “approximate, to be verified on site”. A note such as “Do not scale; all dimensions to be checked on site before ordering” is essential. At 1:50, 60 mm is 1.2 mm on paper - visible enough to matter, so hiding it would be poor practice.
2. Describe the line hierarchy and annotation you would use to distinguish existing stone walls, new blockwork partitions and demolition work at 1:50, using the available 0.18 mm and 0.50 mm pens.
Read the worked answer
Use the heaviest line only for the cut edges of the most important elements - typically external walls and any structural opening - at 0.50 mm. Existing stone walls can be shown with a light poché or grey fill bounded by a 0.35–0.50 mm outline, but avoid dense hand hatching at 1:50 because it obscures the plan. New blockwork partitions should read as new work: 0.50 mm outline with a distinct light fill, or a clear legend keyed to a graphic. Demolition should be dashed, not solid, and clearly labelled; do not rely on line weight alone, because a dashed line at 0.18 mm can disappear in a reduction.
Keep dimension lines, extension lines, leader lines and text at 0.18 mm. Use 2.5–3.0 mm lettering for room names and 2.0–2.5 mm for dimensions. Add a legend on the sheet, even if the symbols seem obvious. The test is whether a contractor can separate retained, removed and new work without reading every note.