House Extensions Services in Hemel Hempstead

GS Renovation builds house extensions in Hemel Hempstead: single storey rear, side returns, wrap arounds and two storey additions. We appoint the structural engineer, build to the calculations, and coordinate the building control applications and inspections. Planning runs on a separate route through Dacorum Borough Council, and we tell you at survey which consents your scheme needs.

A rear extension under construction by GS Renovation, with cavity blockwork built up and the damp proof course laid — Blockwork to damp proof course level, with the membrane dressed over before the next lift goes on.

The plan Dacorum decides your extension against

Dacorum Borough Council is the local planning authority for Hemel Hempstead. Its Core Strategy was formally adopted on 25 September 2013. The Site Allocations Development Plan Document was adopted in July 2017. Saved policies of the Dacorum Borough Local Plan 1991 to 2011, adopted in 2004, remain part of the adopted development plan, so an application is judged against a set of documents rather than a single one.

The council's emerging plan is called the New Dacorum Local Plan, running to 2041. An emerging plan carries weight in decisions before it is adopted, which is one reason a scheme drawn up two years ago is worth revisiting before it is submitted. We are builders rather than planning consultants, so where a scheme looks finely balanced we will say that a planning professional is the right person to advise on it.

Validating the application, and paying for advice first

Dacorum states that it does not currently have any additional local validation requirements for planning applications beyond the national list. It will not validate an application submitted without the Community Infrastructure Levy additional information forms, so those go in with everything else. Application fees are set nationally. Dacorum directs applicants to the Planning Portal fee calculator rather than publishing its own scale.

Pre-application advice is charged separately. Dacorum charges £235 including VAT for written pre-application advice on a householder extension or outbuilding. It charges £475 including VAT for pre-application advice on an extension to a house that is not listed, and £560 including VAT where the house is listed. The council quotes 20 to 30 working days for a response, so that belongs at the front of the programme rather than in the last fortnight before you want to start.

What is under the footprint

Chalk, with different material sitting over it depending on the neighbourhood. British Geological Survey mapping shows Adeyfield with Lambeth Group and Seaford Chalk Formation bedrock, and records the Clay-with-flints Formation as the superficial deposit there. Grovehill is mapped on Clay-with-flints over Seaford Chalk. Bennetts End is mapped on Head over Lewes Nodular Chalk. At Boxmoor the valley floor is Alluvium over New Pit Chalk, with Head on the lower slopes and the higher ground around St John's on Lewes Nodular Chalk with no superficial deposit mapped.

Clay-with-flints is the one to plan around. The BGS records it as up to about 10 metres thick, but very variable where let down into dissolution pipes in the Chalk, and records that those pipes and hollows may be 1 to 50 metres in diameter. A foundation that is straightforward at one corner of a rear extension can meet something quite different at the next. Trial holes and an engineer's foundation design answer that. A geology map on its own does not.

Public sewers and lateral drains

They set where an extension can go. Thames Water requires a build over agreement if you build within 3 metres of a public sewer, and also if you build within 1 metre of a public lateral drain. A Class 1 build over application, where the internal diameter of the sewer is 175mm or less, costs £130. We raise drainage at survey, because moving a proposed wall costs far less than moving a sewer.

The agreement is applied for by you as the property owner, and we prepare the drawings and drainage details it needs. It runs alongside the building control application rather than after it. Where the position of a sewer is uncertain, a drainage survey before the foundations are designed is cheaper than redesigning them once the trench is open.

Brickwork and mortar matched to the existing elevation
Foundations, groundworks and steel frames
Steel goalpost frames where the rear wall opens up
Party Wall Act notices for excavation near a neighbour's wall
First fix and second fix plumbing and electrics throughout

Service areaHemel Hempstead · HP1, HP2 and HP3

Local authorityDacorum Borough Council

Part ofHertfordshire · about 12 miles from our base

Typical homesNew Town corporation estate housing built neighbourhood by neighbourhood

Also covered nearbyBerkhamsted, St Albans, Harpenden, Watford and Rickmansworth

The GS Renovation Difference in Hemel Hempstead

An extension here runs on two separate consent routes, and GS Renovation coordinates both: the planning application to Dacorum Borough Council, and the building control applications and inspections that follow it. We appoint the structural engineer, build to the calculations, and keep the two routes in step so that neither holds up the other. Our founder has over 30 years of hands-on experience. We are fully insured and registered in England, company number 14611254, and you deal with one point of contact from survey to handover.

Insulation and thermal detailing to current regulations
Party Wall notices served for excavation near a neighbour's wall
A written scope and programme agreed before work starts
Weathertight shell reached before the fit-out begins
Fully insured, with cover in place on every site
Structural engineer instructed and coordinated on your behalf

Written and reviewed by Abdelaaziz Saaid, founder of GS Renovation Ltd, who has spent more than 30 years on the tools and on site in London homes. Structural design is specified by the consulting engineer appointed to your project.

FAQ

Frequently Asked Questions about House Extensions Hemel Hempstead

How much should house extensions in Hemel Hempstead cost?

There is no single figure, because house extensions are priced from the survey rather than a rate card. At an HP1 address the cost follows the structure involved, the access, and how much making good the 1930s and interwar construction demands. GS Renovation shows the Dacorum Borough Council building control fee on its own line, and Hemel Hempstead homeowners get that breakdown in writing. You have the written house extensions figure within days of the HP1 visit, anywhere in Hemel Hempstead. As a rough guide, house extensions in London typically starts from roughly £40,000 for a single-storey rear extension and rises with size and specification (indicative London ranges, MyBuilder and Checkatrade, 2026). Your figure depends on the size, specification and condition of the property, which is why we survey before quoting.

Do the Old Town conservation rules apply to an extension in Piccotts End?

Piccotts End is its own conservation area, designated on 6 October 1969, and one of 25 in the borough. Conservation area control applies there in its own right. Piccotts End does not appear on Dacorum's list of completed conservation area character appraisals, so there is no published appraisal setting out what the council looks for. That makes early contact with the conservation team on 01442 228000 more useful there, not less.

There is a mature tree where the extension foundations would go. Is it protected?

Take it that it is, if the property sits inside a conservation area. The Old Town character statement advises that, regardless of whether a tree is covered by a tree preservation order, a tree is likely to be protected if it lies within the conservation area boundary. Works to it are then dealt with through Dacorum before the foundation design is fixed. The conservation team can be reached on 01442 228000.

What shape does a rear extension behind the High Street need to be?

One that follows what is already behind the building line. The character statement asks that the scale, form and massing of existing rear extensions be respected and, where possible, reflected in future alterations and extensions behind buildings fronting the High Street or Queensway. It describes those rear extensions as tall narrow gables projecting perpendicular to the building line, and treats the plot grain, with buildings running down the plot, as very important.

Does the conservation area rule out a side return?

It does not rule one out, but it removes the permitted development route. In the Hemel Hempstead conservation area, planning permission is required for any extension that would extend beyond a wall forming a side elevation of the original house. A side return there is therefore a planning application, decided by Dacorum Borough Council as the local planning authority. We survey and build to the scheme that gets permission, rather than the other way round.

There is a manhole cover where the extension floor will be. What happens to it?

It has to be relocated. Thames Water does not permit internal manholes, so a chamber inside the proposed footprint cannot simply be built over and covered. That work sits with the build over agreement, which Thames Water requires where you build within 3 metres of a public sewer. We raise drainage at survey, because a diverted run can change where the new wall lands and what the foundation has to avoid.

House Extensions Hemel Hempstead

The plan Dacorum decides your extension against

Validating the application, and paying for advice first

What is under the footprint

Public sewers and lateral drains

The GS Renovation Difference in Hemel Hempstead

Rated 4.9 / 5 by our clients

Frequently Asked Questions about House Extensions Hemel Hempstead

More GS Renovation Services in Hemel Hempstead

House Extensions Near Hemel Hempstead

Ready to Start Your Hemel Hempstead Project?