How to plan a home renovation from picking an architect to managing the build

Extending your home or remodeling your kitchen and bathroom may be an exciting prospect but it’s worth carefully planning the design and build to manage the risks involved, according to specialists who spoke to CNBC.

If your project is fairly large, such as a home extension where you’ll be knocking walls down, it’s a good idea to hire an architect because they can guide you through the relevant planning permission and building rules depending on where you live. They can also help you appoint a building contractor (known as a builder in the U.K.).

Write an initial brief — essentially a wish list for your project — before approaching an architect, is the advice of a spokesperson from the U.K.’s Royal Institute of British Architects (RIBA), in an email to CNBC. Think about how you’ll use the new space now and how that might change in the future.

Then, consider your budget before you approach architecture firms, said Richard Parr, founder of design studio Richard Parr Associates. “Do the math before your first meeting,” he said in an email to CNBC.

He also advocates thinking about the “emotional” brief — Parr likes to get to know his clients by asking them questions like how they spend their time and where they like to go on vacation — as a favorite destination might influence their design choice.

Finally, consider green credentials. It’s worth focusing on any sustainability goals upfront, according to Ruth Lang, lead researcher in low carbon housing at the Future Observatory, a research program run by London’s Design Museum.

“Thinking about how your project can make better use of passive heating and lighting, and use reclaimed or natural materials, which have a lower carbon impact, can hugely change the manner in which a project would be conceived,” she told CNBC by email. You can also ask your team how they might minimize waste or repurpose materials, Lang said.

“If you were thinking of taking out a marble kitchen countertop, for example, you don’t have to reuse this in the kitchen again. You could instead consider how the material available could be used in other applications, such as being cut up for bathroom tiling,” she said.

RIBA’s online Find an Architect service asks for details such as your project’s aims and budgets, design style (such as whether you want it to be in keeping with the existing building), your overall aims — including more space, flexibility or more light — plus any restrictions like being in a conservation area.  

In Germany, the Association of German Architects (known as the BDA), has around 5,000 members and you can search its directory by region, while the American Institute of Architects also has a listing of firms that is searchable by state or zip code.

RIBA advises meeting four or five firms in person to see how you get on, and to find out about their portfolio, fees, construction costs and timings. The architect will prepare technical drawings ready for a builder to cost and can recommend what type of building contract you should use too.

You can opt for your architect to be your contract administrator too, meaning that they will oversee quality control during the build, according to RIBA. “If you don’t designate someone to this position, the responsibility falls on you,” its spokesperson said.

Gary Olsen, a chartered builder and director of design and build company Create, said this pre-contract phase is crucial — and not worth skimping on because it can avoid problems later.

Any scope of work document should include costs that “people might not initially think of,” Olsen told CNBC by phone, such as parking permits and fees for dumpster or skip hire. If the builder’s estimate exceeds your budget, write down your hierarchy of needs and wants and ask your contractor if they can revise it accordingly, Olsen said.

When you meet with potential builders, ask whether the person quoting for the work will also oversee it. If not, ask to meet the manager who is likely to be in charge of your build. “I’ve got to be confident that you’re going to be a nice person to work for and I’m going to get paid … And then [customers must consider]: Can I trust this person to deliver what he says?” Olsen said.

The Federation of Master Builders (FMB) has a directory of building contractors, searchable by specialism and location.

Older properties may have structural issues, and it’s worth understanding these ahead of time, Olsen said. Victorian-era terraced properties, typical of the U.K., are sometimes “L”-shaped at the rear, meaning they have an outrigger, the part of the home that projects out into the backyard. Occasionally this can sink in relation to the rest of the building and it’s worth identifying these types of issues before work starts, Olsen said.

“Don’t … hide behind a sofa looking through your fingers, hoping that there won’t be something [wrong]. A defect won’t magically go away by itself,” he said.

If you share a wall with a neighbor (known as a party wall), it is a good idea to get a condition survey of their home before work begins, especially if you are doing excavations. This should include photographs, descriptions and measurements of any existing cracks or defects, Olsen said.

Changing your mind about fixtures and fittings can be expensive if work has started, Olsen said.

For example, if you decide you prefer an engineered wood floor instead of the vinyl one that has been estimated for, it may not simply be the materials that cost more — the concrete base underneath may need to be finished to a different level.

Olsen suggested setting up a WhatsApp group for requested changes, confirming what’s been agreed by email and adding cost details to a spreadsheet.

Olsen, who is board president of the FMB’s London region, said a contractor may ask for around 5% of the build cost to secure the project, followed by about 20% once work begins.

“Be wary of big money payments upfront,” Olsen said. And, if the builder doesn’t provide you with a payment schedule, “don’t sign the contract,” he said. Once the project has been completed, expect to retain about 2.5%, which you’ll pay once you reach the end of an agreed rectification period of about six months.

Try to remain flexible during the project, Parr said: “Renovation is not a precise science or a predictable art, so be prepared for discoveries and the unforeseen. Above all, I always tell clients to follow their gut instincts and make sure they enjoy the journey the whole way through.”