Building Construction and Services Relevant to Interiors
What this domain tests
Questions here check that your drawings are buildable: partition build-ups and thicknesses, opening sizes, ceiling voids for services, coordination of electrical and plumbing points, and safety requirements that an interior scheme must not breach.
Walls and partitions
- Load-bearing masonry and concrete must not be removed without structural engineer approval; non-load-bearing options include 100 mm brick, 200 mm block and stud partitions.
- Drywall build-up: 75/100/125 mm studs at 600 mm centres plus 12.5 mm boards each side, so a 100 mm stud gives a 125 mm finished partition. Add mineral wool and resilient bars for acoustics; party walls to about 53 dB Rw; fire ratings REI 30/60/90 by board type and layers.
- Openings need lintels. A standard 800 × 2,100 mm door leaf needs a structural opening of roughly 900 × 2,100 mm.
Ceilings and services
- Suspended ceilings need a void of 150–300 mm for ducts, cable trays and drainage falls, with access panels at valves and junctions.
- Electrical: socket outlets about 300 mm above floor (1,050 mm above a 900 mm worktop), switches about 1,100 mm, 30 mA RCD protection, separate circuits, IP-rated fittings in bathroom zones.
- Plumbing: 110 mm soil pipe; 40/50 mm wastes at falls of about 1:50 (20 mm per metre); traps with access; 15 mm supplies with isolation valves.
Safety
- Escape routes ≥ 900 mm clear, fire doors self-closing and never propped; keep the door swing clear on escape routes.
- Non-structural elements - ceilings, partitions, tall joinery - must be anchored against seismic load (Eurocode 8, applicable in Cyprus).
- Toughened or laminated glass in doors and low panels; balustrades at 1,100 mm.
Worked example
A bathroom is 2.40 × 1.80 m and the WC is moved 1.20 m from the existing stack. A 40 mm waste needs about a 1:50 fall, that is 20 mm per metre, so 1.20 m gives 24 mm of drop plus the trap depth. Check the available floor zone or ceiling void: if the joists run the wrong way and only 80 mm exists, the options are a low-profile frame with a rear-discharge pan, raising the floor locally, or a macerator (noisier, needs maintenance). The reasoning chain is distance → fall → available void → alternative, and it is written on the drawing as a note.
Traps that cost marks
- Removing a wall without confirming it is non-load-bearing and without an engineer.
- Forgetting the ceiling void, then finding the drainage cannot fall.
- Placing sockets or switches inside a bathroom zone.
- Confusing the door leaf size with the structural opening size.
- Specifying a partition without fire and acoustic ratings where they are required.