Structural materials
Structural materials carry loads and hold the room up: concrete, steel, brick and timber. Their key property is strength: how much squeeze or pull they can take without breaking.
In interior work, structural parts include partition frames, wooden studs, joists and concrete or brick walls. They must also be stable: they must not bend or rot over time.
Functional materials
Functional materials do a special job, not mainly carry loads.
- Heat insulation: mineral wool, foam. They block heat flow, so rooms stay cool in summer and warm in winter.
- Sound insulation: soft, thick layers that absorb sound.
- Fire protection: gypsum board and fire boards slow the spread of fire.
- Moisture barrier: sheets that stop damp.
Finishing materials
Finishing materials make the final surface: paint, plaster finish, wallpaper, wood veneer, vinyl and tiles. We judge them by look, wear, cleaning and water resistance.
Wet rooms need finishes that do not soak water. Floors need finishes that resist rubbing (wear). Children’s rooms need safe, non-toxic finishes.
Unit materials
Unit materials come in pieces of a fixed size: tiles, bricks, boards and panels. They are counted.
Number of pieces = area ÷ area of one piece. Always add about 10 per cent for cutting and breaking. Example: a floor of 12 m² with tiles of 0.5 m × 0.5 m (0.25 m²) needs 12 ÷ 0.25 = 48 tiles; with 10 per cent extra, about 53.
Properties and how to choose
Main properties: strength, heat blocking, fire safety, water resistance, wear resistance, cost and look. Make a short list of what the room needs. Kitchen: fire safety, water proof and wear. Bedroom: warmth and comfort. Bathroom: water proof first. Then pick the material that has these properties.
Also check health and safety: low fumes, no slippery floors in wet rooms.
Key formulas and definitions
- Number of pieces = area ÷ area of one piece
- Order quantity = number of pieces × 1.10
- Area of a rectangle = length × width
- Best material = highest score for what the room needs
Worked examples
1. A floor is 4 m × 3 m. Tiles are 0.5 m × 0.5 m. How many tiles (no extra)?
Area = 12 m². One tile = 0.25 m². Tiles = 12 ÷ 0.25 = 48.
2. For the same floor, order with 10 per cent extra. How many?
48 × 1.10 = 52.8, so order 53 tiles.
3. Which family is mineral wool in and why?
Functional. Its job is to block heat, not to carry loads or give a final look.
4. Pick a floor finish for a bathroom and give two reasons.
Ceramic tile (or a tile with a rough surface). It is water proof and tough against wear. A rough surface also reduces slipping.
Common mistakes
- Thinking paint is structural. Paint only gives a finish.
- Ordering the exact number of tiles. Cutting and breaking need about 10 per cent extra.
- Choosing a material only for its look. Strength, water and fire needs come first.
- Forgetting that gypsum board and wool are poor at carrying loads.