External Works

External works are the stage everyone forgets to budget for. Construction traffic churns up lawns, compacts subsoil, cracks the existing patio and damages boundary fences. The builder's quote usually ends at the rear door threshold, so the reinstatement cost lands with you at the point in the build when cash is tightest.

These guides cover the materials that make the outside of your extension look finished: paving for the new patio or path, topsoil and turf to reinstate the lawn, and fence panels and posts for a boundary that took a battering. Each page explains what to specify, how much you need, and the preparation underneath that decides how long the job lasts.

Where to start

Read paving slabs first. The sub-base is where most of the cost and all of the durability sit, and the patio has to finish below the damp proof course with a proper fall away from the house. Next read topsoil, because the decision to keep site-won soil or import fresh is made at groundwork, long before anyone lays turf. If the fence needs replacing, fence posts matter more than the panels they hold.

The guides, grouped by job

Hard surfaces. Paving slabs in concrete, natural stone and porcelain, with slip ratings, falls and jointing.

Lawn. Topsoil grades and depths, then garden turf, including the laying window and the first fortnight of watering where new lawns most often die.

Boundaries. Fence posts and fence panels, including the planning height limit, who owns the fence, and how to raise it with your neighbour.

Where these fit in the build

This work sits in garden and external works at the end of the build, and the snagging checklist is where you check falls, DPC clearance and joints before you sign off. Topsoil is stripped and stockpiled during foundations and footings. To price reinstatement before you sign the builder's final account, use the garden reinstatement cost calculator.