We are extending the kitchen at the back of the house; what should we get right while the walls are open?
A rear kitchen extension is one of the few moments when the fabric of the house is genuinely accessible. The decisions that matter most are the ones that become expensive or impossible the day the plasterer arrives: how the floor is insulated, where the cables and pipes go, whether the glazing is the largest source of summer heat or winter loss. Heating and cooling kit come last, and they come easier when the rest of the work has been done thoughtfully.
The moment
A short scene that puts you in the room where the decision actually gets made.
The architect has drawn something beautiful, the builder has given a date, and somewhere on the budget spreadsheet there is a line called Mechanical and Electrical that nobody has properly priced. This is the moment to slow down for a fortnight.
The typical order
What to decide, in roughly this order.
Fabric first, services second, kit last. Each step is listed in the sequence we would work through it, because doing one out of order tends to make the next one harder than it needed to be.
A rear kitchen extension with the architect's beautiful glazed gable facing south-west. This is the moment to make the right decisions.
Before the drawings are signed off
Decide where the glazing faces and how it will be shaded
A south or west facing glazed gable looks wonderful in the architect's render and behaves like a greenhouse in July. External brise-soleil, deep reveals or a planted pergola cost a fraction of retrofitting cooling later.
Before the slab is poured
Specify floor insulation to current building regulations as a minimum, and consider better
The floor is the one element you cannot revisit. Adding fifty millimetres of higher-performance insulation now is trivial; doing it in five years means lifting the kitchen.
First fix
Run conduits for future underfloor heating, EV charging, solar and a battery, even if you are not installing them yet
A length of empty conduit costs almost nothing while the walls are open and costs a fortune once they are closed. The homeowners who regret this most are the ones who said we will deal with it later.
First fix
Decide if the boiler stays, moves or goes
An extension changes the heat demand of the house and often changes where the cylinder needs to live. If a heat pump is on the horizon, the cylinder and pipework specification differ from a combi swap.
Second fix
Install mechanical extract that is actually quiet and actually ducted to outside
A loud recirculating hood over an island is the single most regretted kitchen decision we hear about. A ducted extract through the wall, sized to the hob, transforms how the room feels to live in.
Before snagging
Commission the ventilation and run the heating through a full cycle
Defects found in week one are defects the builder fixes. Defects found in month six are defects you live with.
Watch-outs
The mistakes we see often enough to mention them in writing. Some are expensive; all are avoidable.
- A glazed gable wall facing south or west, with no external shading specified, is the most common source of overheating in modern extensions.
- Underfloor heating installed without a proper screed depth or a low-temperature designed flow will run hot and inefficient for the life of the house.
- The boiler being relocated by a plumber who is not the one who will commission it usually leads to balance and pressure issues the homeowner discovers in October.
Problems this often resolves
Read these first if you have not started the project yet. They explain what to rule out before any product is on the table.
Technologies in scope
Likely to enter the conversation at some stage. Each links to an honest write-up rather than a sales page.
The pattern above is not a checklist; it is an order of operations. The homeowners who finish a project like this one and look back without regret are almost always the ones who refused to be hurried at the start, did the fabric work before the kit, and brought in the heating engineer before the plasterer rather than after.
Open the Home Planner
Test these decisions on a model of a UK home before any of them have to be made in real life.