Basement Conversions in Portsmouth (83)
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BuilderExtensions / ConversionsConcretingSustainable ConstructionGarage ConversionsServices & skills
BuilderExtensions / ConversionsSuspended CeilingsGarage ConversionsBrick / Concrete Structural RepairsServices & skills
BuilderExtensions / ConversionsLoft ConversionsRepair and Listed Building SpecialistSustainable Construction- N
Services & skills
BuilderExtensions / ConversionsGeneral BuildingSustainable ConstructionConcreting Services & skills
BuilderExtensions / ConversionsBasement / Cellar ConversionsLoft ConversionsProject ManagementServices & skills
BuilderExtensions / ConversionsStretched CeilingsSuspended CeilingsPartition WallsServices & skills
BuilderExtensions / ConversionsConcretingGarden StudiosSteel Work DesignServices & skills
BuilderExtensions / ConversionsCladdingFoundationsGarage ConversionsServices & skills
BuilderExtensions / ConversionsProject ManagementPeriod Property RestorationNew BuildsServices & skills
BuilderExtensions / ConversionsCar PortsRefurbishmentsFire and Flood RenovationServices & skills
BuilderExtensions / ConversionsGarage ConversionsWall Tie ReplacementsBrick / Concrete Structural RepairsServices & skills
BuilderExtensions / ConversionsNew BuildsGarage ConversionsRefurbishments
Conversion and extension builders in Portsmouth
Planning a loft conversion, garage makeover or full house extension in Portsmouth? You’re in the right place. Whether you’re adding space for a growing family, upgrading your layout or increasing your home’s value, we can help you find the right tradesperson for the job.
Find extension and conversion builders in Portsmouth
Every builder on Checkatrade passes up to 12 checks before they appear in your search. You can read verified reviews, compare services, and even post your job to get quotes straight to your inbox, all in a few clicks. That’s how we help homeowners like you get a job done right.
What to expect from hiring an extension or conversion builder in Portsmouth
Our checked tradespeople in Portsmouth cover a wide range of projects, including:
Single or double-storey house extensions
Kitchen and diner extensions
Loft, attic, garage or basement conversions
Garden room extensions
Utility room extensions
Over-garage extensions and side returns
Costs to expect
Costs of extensions and conversions vary depending on size, structure and spec, but here's a rough guide:
Single - storey extensions: £21,000 - £65,000
Double - storey extensions: £55,000 - £95,000
Loft conversions: £35,000 - £65,000
Garage conversions: £8,000 - £20,000
What to check before you hire:
- Are drawings or planning permissions needed?
- Are they familiar with building regs?
- Is the quote fixed or flexible?
- Does it cover materials and project management?
Most builders will include prep, construction, electrics, plumbing and final finishes in their quote, but always double-check. Timelines range from a few weeks for simple jobs to several months for bigger builds.
Extension and conversion builders in Portsmouth: Homeowners vs renters
Homeowners:
You’re in charge of the project. That means hiring the builder, securing permissions, and paying for the work. You may need:
Planning permission (especially for double-storey builds or changes near boundaries)
Drawings from an architect or structural engineer
Building regs approval
If you’re not sure where to start, speak to a local builder or post your job to get help with the process.
Renters:
You’ll usually need your landlord’s approval to make any big changes. In most cases, your landlord will be the one arranging and paying for structural changes like loft conversions or extensions. That said, it’s worth flagging ideas if you think they’ll improve the property, especially if it means longer tenancies or fewer repairs.
Emergency extension or conversion help in Portsmouth
Extensions and conversions are big projects, but sometimes, things go wrong and need sorting fast. Common urgent issues include:
Leaks in newly converted lofts
Structural cracks or shifting
Faulty electrics or plumbing in newly added rooms
Incomplete work by previous builders
Facing an emergency in Portsmouth? Enter your postcode or post a job to find emergency services in your area.
Find the right extension or conversion specialist in Portsmouth
Looking for a builder to help with:
- Rear house extensions
- Kitchen extensions
- Garage conversions
- Loft or attic conversions
- Garden room builds
- Basement or cellar conversions
- Conservatory roof upgrades
- Utility or porch extensions
Looking for more tradespeople in Portsmouth?
Find Checkatrade reviewed Tradespeople, get a quote today, discover related services in Portsmouth and check out our latest home improvement guides.
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