Hard Landscaping After a Home Extension

Introduction

The hard landscaping of the rear garden is an integral part of the design of a rear extension project — the terrace, steps, paths, boundary walls and planted areas immediately adjacent to the house determine how well the extension connects to the garden and how the outdoor space is experienced day-to-day. In north London where rear garden sizes are limited, a well-designed hard landscaping scheme extends the usable living area of the house into the garden and creates an outdoor room that functions in continuity with the interior. This guide explains how to approach hard landscaping design following a rear extension, covering materials, drainage, levels, planting integration, and cost.

The Relationship Between Extension and Garden

The most important design decision in hard landscaping is the relationship between the internal floor level and the garden terrace level. Options include:

• Flush threshold: The terrace immediately outside the extension is at the same level as the internal floor, with only a 10–15mm threshold step for weather exclusion and drainage. This creates the most seamless connection between inside and outside — visually and functionally the space reads as continuous. Requires careful drainage design to prevent water ingress to the extension.
• Single step down: A single step (typically 150mm) from the extension floor to the terrace level. More common in practice — allows a larger drainage channel or gutter at the base of the external doors and provides a visual threshold between inside and outside.
• Multiple steps: Where the existing garden level is significantly below the extension floor level (common in properties where the garden is lower than the ground floor due to topography), a flight of steps from the extension terrace to the garden is required. Step design should be consistent with the terrace material and proportion — generous treads (minimum 300mm) and modest risers (maximum 175mm) produce comfortable, safe external steps.

Terrace Design and Materials

Natural Stone Paving

Natural stone is the premium choice for garden terraces in north London — limestone, sandstone, slate, granite and basalt are all used. Key considerations:

• Limestone: Warm cream and buff tones; moderate slip resistance when honed (anti-slip surface treatment required for external use); compatible with contemporary and period settings. Requires sealing to resist staining from leaves and moss.
• Sandstone: Natural warm orange-buff tones; good slip resistance due to granular surface; traditional appearance appropriate for Victorian garden settings.
• Granite: Very hard, durable and low maintenance; available in grey, pink and black tones; flamed or sawn finish for external use. Contemporary aesthetic; more industrial character than limestone.
• Slate: Dark grey; contemporary character; moderate slip resistance when riven; requires care in freezing conditions.

All natural stone should be laid on a full cement mortar bed (not spot-bedded) on a suitable sub-base to prevent differential settlement and edge lifting. Joints should be pointed in a lime or cement-based pointing mortar appropriate to the stone type.

Porcelain and Ceramic Paving

Large-format porcelain paving (600 × 600mm to 1,200 × 600mm) has become a widely used contemporary terrace material. Advantages include consistent colour and tone, low maintenance, frost resistance, and the ability to match or coordinate with internal floor tiles for a visually continuous inside-outside treatment. Porcelain requires a full mortar bed and appropriate jointing. Coordinating the internal and external tile specification — with a continuous floor material extending from inside the extension to the terrace — is a design feature of many high-quality rear extension projects.

Timber Decking

Hardwood decking (typically Ipe, Cumaru, Bangkirai or Garapa) creates a warm, tactile terrace surface. Timber decking sits on a raised frame that can accommodate level changes, drainage and service runs below. Annual oiling maintains the appearance; untreated hardwood weathers to silver-grey. Composite decking products offer low-maintenance performance but typically lack the warmth and natural quality of solid hardwood.

Drainage Design

Proper drainage design is critical in rear garden terraces. From 2008, SuDS requirements apply to hard surfacing exceeding 5 sqm — non-permeable surfaces require runoff management. Key drainage elements:

• Paved surface falls: All paved areas should fall away from the building at a minimum 1:60 gradient (preferably 1:40) to channel surface water to drainage points
• Channel drain at extension threshold: A linear channel drain at the base of the external doors collects water before it can reach the threshold, particularly important with flush or near-flush threshold details
• Soakaway or surface water drain: Collected water must discharge to a soakaway (where ground permeability allows) or to the surface water drain. Connecting to the foul drain is not permitted.
• Permeable paving: Permeable block paving, gravel, resin-bound aggregate or open-jointed paving allows water to infiltrate through the surface, reducing runoff and meeting SuDS requirements without a separate soakaway

Boundary Walls and Planting

Hard landscaping integrates with soft landscaping — planting beds, raised planters, trees and lawn. The boundary between hard and soft landscaping should be designed as part of the overall composition:

• Raised planters in brick, stone or rendered blockwork define planting areas and provide a visual transition between the terrace and planting beds
• Retained soil edges should be contained by low edging or a kerb to prevent soil migrating onto the terrace
• Tree positions, particularly existing trees under Tree Preservation Orders, must be considered in relation to the terrace layout — roots can damage paving and foundations, and the drip line of trees affects paving durability

Garden Lighting

External lighting integrated into the hard landscaping scheme extends the use of the terrace into the evening and provides security. Typical lighting elements for a rear terrace include:

• Wall-mounted lanterns at the extension elevation — flanking the rear door or at regular centres along the external wall
• Recessed ground lights in terrace paving — IP67-rated recessed luminaires flush with the paving surface, casting low-level light across the terrace
• Spike-mounted spotlights in planting beds — highlighting specimen trees or architectural planting
• Step lights — strip or recessed lights at step edges for safety and ambience

All external lighting should be on a dedicated circuit with a weatherproof external socket for flexibility, and circuits should be connected to the internal lighting control system to allow scene setting and automation.

Costs

Conclusion

Hard landscaping design is not a minor afterthought to a rear extension project — it is an integral part of the design that determines whether the indoor-outdoor connection achieves its potential. The terrace material, level relationship, drainage design and lighting together define the quality of the outdoor space as a usable extension of the interior. In north London where rear gardens are compact and the terrace may constitute the majority of the usable outdoor space, investing in a properly designed hard landscaping scheme produces returns in daily enjoyment and long-term property value. An architect designing the extension will typically include the hard landscaping design within the project scope, ensuring that the terrace and garden work as a coherent whole with the building.