One of the first questions most homeowners ask before starting any building work is simple: how much will it cost, and how long will it take? The timeline depends on the type of job, the size of your property, and the amount of preparation work required. Contractors often need to complete this preparation before they can begin the main work. This guide breaks down what tends to affect cost and timing across the most common building services in London, so you can plan and budget with a bit more confidence.

What affects the price of building work?

A few things tend to drive the cost of any project. The size and scope of the job matters most, but access also plays a part. Terraced houses on narrow London streets can be harder to work on than a detached property with a driveway. The condition of the existing structure matters too. A roof that just needs a few tiles replacing costs far less than one that needs stripping back completely. Materials also vary in price, so the finish you choose, such as the type of render or decking, will affect the final figure.

Roofing work

Roofing costs vary enormously depending on the type and size of the job. A small repair, such as replacing a handful of damaged tiles, is a relatively quick and affordable job. A new roof is a much bigger undertaking that can take several days to complete. Flat roof work tends to be quicker than a full pitched roof replacement, but it still needs to be done properly to avoid leaks further down the line. General roof repairs fall somewhere in between, and a good contractor will always inspect the roof first and give you a clear quote before starting.

Chimney work

Chimney jobs range from a quick repair to a much larger rebuild. Contractors can usually complete repairs, such as repointing loose mortar or replacing a cracked chimney pot, within a day or two. A full chimney rebuild is a bigger job, since it often involves scaffolding and takes longer to complete safely, especially on taller London terraces.

Rendering, damp proofing and waterproofing

Rendering a property usually takes anywhere from a few days to a couple of weeks, depending on the size of the house and the type of render used. Weather plays a part too, since render needs the right conditions to dry properly. Damp proofing timelines depend heavily on the cause of the damp. A straightforward fix may only take a day to complete. More serious problems, such as rising damp that affects several walls, usually take longer to repair properly. Waterproofing projects also vary in length. The size of the area and the ease of access both affect how long the work takes.

Extensions and renovations

House renovations and extensions are usually the biggest projects in terms of both cost and time. A single-storey rear extension can take several weeks from start to finish once you include groundwork, building, and finishing touches such as plastering and decorating. Before work begins, check whether your project needs planning permission or falls under permitted development rules. The Planning Portal has clear guidance on this, and getting it right early avoids costly delays. Some projects also need sign-off from building control, so it is worth checking the GOV.UK guidance on building regulations approval beforehand.

Garden and outdoor projects

Outdoor work tends to move faster than structural building projects, weather permitting. A garden renovation can take anywhere from a few days to a couple of weeks, depending on the scope of the work. Landscapers may lay turf, plant gardens, or complete hard landscaping during that time. Once they finish the groundwork, they can usually pave a driveway or patio within a few days. They can often build a new deck in a similar timeframe. Fencing is generally one of the quicker jobs, while wider landscaping projects that combine several elements naturally take longer.

Plastering, painting and interior work

Interior jobs are usually quicker than structural work outside, but they still need time built in for drying and finishing. Plastering needs time to dry properly before you can paint over it, so rushing this stage often leads to a poor finish. Once the plaster is ready, decorators can often paint and finish a single room within a day or two. A full house redecoration naturally takes longer.

Getting an accurate quote

Many factors affect the cost and timeline of a project. For that reason, you should arrange a proper site visit and request a written quote. This is the most reliable way to understand exactly what your project will involve. Be cautious if a contractor provides a quote without inspecting the property first. Only an in-person inspection can identify hidden issues, such as damp behind old plaster or rotten roof timbers. A detailed quote should also give you a realistic idea of the timescale, not just a price.

In summary

The size, condition, and complexity of the job all affect the cost and timeline of building services in London. Practical factors, such as access and weather, also play an important role. Contractors should inspect the property before providing a written quote. A detailed quote helps you understand the project’s cost. It also gives you a clearer idea of how long the work will take and how it may affect your daily routine.