German prefab extensions

What German factories do differently

Most German prefab is closed-panel timber frame. Each wall leaves the works with insulation, vapour control, a service void and plasterboard on the inside, cladding or render board on the outside, and triple-glazed windows already sealed in. Much UK timber frame still arrives as open panels to be filled on site.

The result is speed and consistency. A single-storey extension shell can be weathertight in a day or two, and the airtightness that British builders chase with tape and mastic is largely settled before the panels are loaded.

German makers also tend to be signed up to factory quality schemes run by their national prefab association, with outside inspectors visiting the works. Ask which scheme a maker belongs to and for the certificate.

Why German prefab extensions prices are hard to find

There are three reasons. German firms sell houses first, and price extensions as one-off projects. The quote depends on how much they do: shell only, shell and fit-out, or everything above the slab. And haulage, a travelling erection crew and the exchange rate all move the total.

So compare like with like. Ask every bidder, German or British, for a price to the same finished stage, with foundations, the opening into the house and VAT shown separately. If a German shell price looks close to £2,200 per m², check what is missing.

How ordering works

Expect a longer run-in than with a UK firm. After a site visit and outline design you sign a contract and the maker's engineers produce factory drawings. Many firms then invite you to a showroom, often in Germany, to pick every finish and fitting in a day or two. Once that is fixed, changes are costly.

A UK groundworker builds the slab to millimetre tolerances from the factory drawing. The panels arrive on a booked date with the maker's own crew, and the shell goes up in days. Order books can be full for many months, so get the build slot in writing.

UK rules still apply

A German extension needs the same consents as any other. Planning follows the usual permitted development limits or a householder application. For building regulations, the maker should give building control structural calculations to UK standards and evidence for fire, insulation and ventilation. German factory U-values are normally well inside the English targets of 0.18 for walls and 0.15 for roofs.

Ask early about electrics: wiring must meet British standards and be certified by a UK-registered electrician. And ask who gives the warranty, for how long, and whether a UK insurer stands behind it.

When a UK maker is the better choice

For a single-storey room under about 30 m², a British closed-panel or insulated-panel firm will usually be cheaper, quicker to start and easier to chase if something needs fixing. See our pages on flat pack extensions and prefab extension kits. German prefab earns its premium on bigger, glassier, more demanding projects.