What adds value to a house in Derry? Check before you spend

Separate repairs, extra uses and personal preferences

Start with three lists: faults to investigate, changes that solve a practical problem, and finishes you personally prefer. A leaking roof, a missing workspace and a kitchen colour choice are different decisions. Do not give them the same assumed return simply because each costs money.

Ask an agent which current features are likely to cause questions, then obtain appropriate professional advice or quotes for the work itself. Keep the cost, disruption, permissions and evidence for any price change separate. No single upgrade adds a dependable percentage to every Derry home.

The garden-room example below shows how to examine one proposal. Use the same decision structure for other work, but obtain the specific construction and consent advice it needs.

For other common projects, compare driveway and parking checks with the overall needs of the house.

For glazing and heating information, read the energy performance guide.

Useful extra space is not a guaranteed return

A garden room gives a buyer another possible use for the property. That is different from proving that the next buyer will repay its installation cost. Treat any fixed percentage uplift as a claim to investigate, not a number to add to an online estimate.

Start with the decision you actually face. If you want an office for several years, the benefit to you belongs in the decision. If you expect to sell shortly, ask an agent to compare the home as it is with the proposed finished result before committing to the work.

Write down what the room can genuinely do

Measure the usable internal space and note the route from the house, lighting, sockets, heating, insulation information and any visible moisture. A desk fitting into a photograph does not establish that the room is comfortable through winter. Keep unknown construction details marked as unknown.

Make a simple use test: can someone close the door, move around the desk and store what they need without blocking access? Look at the space left outside as well. The new room and the garden it occupies have to be judged together, rather than counting the room as a gain and ignoring what it replaces.

Check the documents before changing its description

Northern Ireland planning guidance says permitted development has conditions and advises checking proposals with the local planning office. A separate residence in a garden is not the same proposition as a home office. Do not describe an outbuilding as an extra bedroom or independent accommodation on the strength of a sales brochure.

Keep the installer specification, dated invoice, guarantees and any relevant planning or building-control records together. Ask the council and your solicitor what applies to the particular building and proposed use. This guide cannot decide whether an individual structure has the required consent.

Ask for a comparison you can interrogate

For each comparison an agent provides, record the property type, location, main-house size, garden space, condition, date and whether the figure is an asking price or completed sale. Ask what makes the garden room relevant to that comparison. One more expensive listing does not isolate the value of this feature.

Request two explanations: how the room affects the likely marketing audience, and whether there is evidence for a different price range. It is reasonable for the first answer to be more confident than the second. If the room is unusual, an in-person appraisal is more useful than trying to force its cost into a calculator.

A decision sheet before you spend

Keep four separate lines: the problem the room solves for you, the full quoted project cost, the space or flexibility it removes, and the resale evidence still needed. Include access, foundations, electrics and finishing in the quote questions, rather than assuming the advertised structure price covers the finished project.

Use a whole-property guide range as context, not a second price to which the project bill is added. If you already own the room, present its condition and documented use clearly; there is no need to make a promise about the buyer’s future return.

For the rest of the property, use the pre-sale valuation checklist before asking for an appraisal.