What is a terrace?
A terrace is a level, paved outdoor area directly next to or near a building, intended for sitting and spending time outside. It can be at ground level (in the garden, often called a patio in British usage), on a roof (roof terrace) or raised on a substructure (deck). In landscape architecture, a terrace is also a flat, horizontal step cut into a slope.
Build-up of a ground-level terrace
- Excavation: remove topsoil and soft ground down to a firm layer.
- Sub-base: a compacted layer of crushed aggregate, thicker for heavier loads.
- Bedding layer: a level layer of sharp sand or grit or (for large slabs) a bound mortar bed.
- Surface: slabs, block pavers, natural stone, porcelain paving or timber/composite decking on a substructure.
- Joints: sand, bound jointing compound or open joints, depending on the material and the desired permeability.
Tips
- Fall: give the terrace a slight fall away from the house (around 1 to 2 percent is commonly used) so rainwater does not stand against the wall.
- Height at the wall: keep the surface below the door threshold and the damp-proof course, so water cannot enter the house or wick into the wall.
- Rainwater: large sealed surfaces load the sewer. Consider permeable paving or some planting; some local authorities set requirements for this.
- Permits: a ground-level terrace usually needs no permit. A roof terrace, raised deck with railings or a canopy may require permission depending on local rules; check with your municipality or planning authority.
Common mistakes
- A sub-base that is too thin or poorly compacted, so slabs sink.
- No fall, or a fall towards the house.
- Timber decking directly on the ground: make sure air can circulate under the timber.
Related terms
- Slope
- Paver pedestal
- Decking board
- Grass grid tile
- Split tile
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