Foundations and services for a garden outbuilding: what a "simple" build still needs checking
Even a modest garden building needs its foundation matched to the actual ground, and needs power, water or drainage runs planned properly if they're going in. The checks are smaller in scale than a house, not different in kind.
'It's just a shed' is doing a lot of work in a sentence that's often followed by a genuinely useful, heated, powered building with a WC. The scale is smaller than a house, but the underlying physics of ground, structure and services is exactly the same — which means the same checks apply, proportionately, not a lighter version of them.
Foundation choice still depends on the ground, not the building's size
A small building doesn't mean small foundation risk if it sits on made ground, shrinkable clay near a tree, or a corner of the garden that's genuinely sloping and has never been checked. A trial pit or two, and a look at what's growing nearby, is proportionate even for a modest structure, because the failure mode — a cracked slab, a leaning structure — is the same physics as a house, just cheaper to get wrong at this scale, and cheaper still to get right.
Slab-on-grade versus a proper strip or pad foundation
A simple raft or reinforced slab is usually adequate for light garden buildings on reasonable ground. Anything heavier — masonry construction, a green roof, a mezzanine floor — or built on poorer ground needs a foundation genuinely designed for the actual load and ground conditions, not assumed adequate purely because the building is described as a shed or a garden room.
Running power safely, not just running a cable
An armoured cable, correctly buried at the right depth with warning tape above it, protected by an appropriately rated circuit and, depending on distance and load, its own RCD protection, is a job for a qualified electrician under Part P of the Building Regulations. A garden building's electrics are a common source of both fire risk and non-compliance where this gets treated as a simple extension-lead job rather than a proper installation.
Water and drainage, if the outbuilding needs either
A garden room with a WC, or a workshop with a sink, needs a foul drainage route — for anything beyond a short gravity run to the existing system, that usually means either a pumped connection or a small dedicated treatment solution. Worth establishing the route and the available fall before the building is designed around a bathroom that then can't actually drain without a pump nobody budgeted for.
Building Regulations still apply above certain thresholds
Many garden outbuildings under 15m² with no sleeping accommodation are exempt from Building Regulations, but that exemption narrows quickly — a building over 15m² but under 30m² loses the exemption if it's within 1 metre of a boundary or contains fixed combustion appliances, and any building intended for sleeping accommodation needs full Building Regulations approval regardless of size.
Insurance and mortgage implications people forget
A substantial garden building can affect buildings insurance — worth notifying the insurer rather than assuming it's automatically covered — and, if let out or lived in even informally, can affect the terms of the mortgage on the main house. Worth checking both before the building is finished and in use, not after.