Example prices




Please note that all prices shown here are net of VAT @ 20%

So that you can get a reasonable idea of the budget you would need to make allowance for, the following are approximate prices based on the average loft conversion projects carried out on properties in good condition in recent years. Please note that every single project is quoted individually, and prices vary according to size, condition of the property, cost of selected materials and so forth.

Example 1: Terraced property

Typically, this type of property has two gable (vertical) sides and pitched (sloped) front and back roofs.

  • Option 1 Velux conversion : Fit Velux roof windows to front and back roof slopes to create a new bedroom, accessed by new stairs positioned above the existing stairs. £22,500 + VAT
  • Option 2:Dormer conversion Rear roof slope replaced with full length dormer, front roof slope fitted with two Velux roof windows. The dormer increases the usable loft space and head height to create a new bedroom (with possible en suite), accessed by new stairs positioned above the existing stairs. £25,000 + VAT

Example 2: Hip-ended semi-detached property

Typically, a two-hipped roof, with three sloping elevations (front, back and side), with the adjoining wall being a brick-built gable.

  • Option 3: Side Dormer Side roof slope fitted with access dormer (to accommodate new stairs). Front and back roof slopes fitted with Velux roof windows to create new bedroom with new stairs positioned above existing stairs. £24,500 + VAT
  • Option 4: Hip to Gable Side roof slope rebuilt as gable end (vertical). Rear roof slope changed to full length flat roof dormer, front roof slope fitted with two Velux roof windows. the dormer and gable end increase loft space and head height to create new bedroom and en suite, with new stairs positioned above existing stairs. £32,000 + VAT 

What we include in our price

  • Full survey, working drawings with structural calculations, the Building Inspector’s inspection fee, full Building Regulations approval.
  • Suspended floor
  • Insulated walls and ceilings
  • Hinged access door to floored eaves space
  • UPVC windows, fascia and soffits
  • Traditional staircase made to match existing stairs
  • Electrics
    • 4 No. double sockets
    • 1 No.Pendant light
    • 3 No.smoke detectors
    • Two-way light to stairs
    • Alterations to existing electrics to accommodate building works
    • Testing & certification
    • All electrical works are carried out in strict accordance with BS7071 the IEE Wiring regulations and are test and certificated in accordance to the part P building regulation scheme
  • Plumbing
    • One-sized radiator pipes for bathroom towel rail
    • Supply and fit one radiator with thermo static valves
    • Plumb in bathroom suites
  • Carpentry 2nd fix (skirtings, architraves, doors etc)
  • Plaster finish
  • Waste removed from site, leaving the premises clean and tidy

What we do not include in our price

  • Bathroom suites
  • Ceramic tiling
  • Preparation for decorating and the decorating itself
  • Wardrobes 


With older properties, there may be areas that will need attention during the course of building your loft room that are impossible to predict at the time of preparing your estimate. The most common problems encountered are:

  • Existing roof tiles and lead flashing in bad repair
  • Rotten fascias, guttering and down pipes
  • Electrical systems that do not meet modern safety standards
  • Pest control
  • Unstable chimney stacks
  • Unstable larthen plaster ceilings

Should we encounter any problems of this kind, we will of course notify you immediately and discuss the best course of action and the potential costs involved. We recommend that you make an allowance for such contingencies in your budget when planning the project. 

Frequently asked questions for Loft Conversions

What is a velux conversion?

A velux conversion is one that uses roof light windows installed into the pitch of the roof to give light. There is no visible extension of the loft beyond the existing roof line therefore planning permission is not required.

What is a dormer window?

A dormer window is the exterior part of the conversion that is built at the rear of the roof to provide floor and living space and is generally a square section construction to maximise the overall living area.

What is meant by hip to gable?

This is when we extend the ridge line of a hip-end roof to make it into a gable-end roof. This gives you a much larger loft area. A hip to gable extends the ridge line from the existing hips to overall the flank wall of the house. It will effectively add on the required space to enable the staircase and the shower-room to be built and also increase the standing space available in the loft.

Where will the staircase go?

The staircases in almost all conversions are positioned above the existing staircase of the house. They start at the side of the bedroom door and climb upwards along the flank wall of the house and land at the top level with the new loft floor. This means that no extra space is needed or taken away from the first floor living area to accommodate the stairs into the loft.

Will the loft require planning permission?

All houses have a permitted development (P.D) allowance allocated by the local authority. If the house has no extensions, typically on the ground floor (kitchen,lounge etc) then the loft conversion will not need planning permission as no P.D has been used. However if a property has been extended (even if the current owners purchased it that way) then the volume of the extension would have to be calculated and then subtracted from the P.D allowance to decide if there is enough P.D left to build the loft. If there is insufficient allowance left then planning permission would be required from the local authority.

Do we require a Party Wall Agreement?

The answer is always yes when converting the loft as there are R.S.Gs or steel beams inserted into the loft and they are positioned to rest on and inside the party wall. Even though the beams only rest on your half and not the neighbours, a Party Wall Agreement has to be entered into to avoid any disputes arising once the work has commenced.

How long will the conversion take to complete?

Typically, a rear dormer loft conversion on a terraced property will take 6 and a half weeks to complete and a Gable end and rear dormer on a semi-detached property will take 10 and a half weeks to complete. These timings are an accurate guideline as we have had the same team that convert the loft and they have been with us for more than 10 years. We manage  labour and therefore do not get let down by outside trades not showing to complete their part of the conversion. This means, barring exceptional weather conditions, we are confident of our agreed timescale with the customer.

Are Loft Conversions built during the winter as well as the summer months?

Yes, we work twelve months of the year. It’s a nice position to be in as our order books are always very good due to our high volume of customer recommendations. Especially in the winter months, Joseph James Loft Conversions build your loft to a system that makes sure that you the customer are never exposed to the weather at any time during the construction period. The summer months are no different.

Does French and Thorley obtain planning permission and building regulations or do we do this?

Yes, we can apply and gain all relevant planning and building regulations on behalf of their customers. We use our own architect to produce the plans and he submits them and the applications for planning and building permission to the local authority for their approval. This is all included in the  price contract that we present to you.

After they give permission for the loft conversion are the Local Authority involved? If so how?

The Local Authority is involved from the start to the finish of the conversion. They first receive the plans submitted by the architect and check all the structural calculations through the Borough Engineer’s department. Once these have been confirmed along with all the relevant building regulations for loft conversions, an approved set of plans are returned and the work can then commence. During the various stages of the work, a building’s inspector from the local authority arrives to make sure all the structural work and building regulations are being implemented in the construction of your loft conversion. After the completion of the work a final inspection is carried out. Once this has been confirmed as meeting all the requirements, a completion certificate is sent to the homeowner confirming that the loft conversion they have had built on their home complies with the building regulations covering England and Wales.

Can any loft be converted?

Nearly all lofts or attics can be converted as long as they are not breaching planning or conservation guidelines. However, it depends also on the height of the ridge. If you were to stand in the centre of the roof and measure from the top of the existing ceiling joists to the top of the ridge board at the apex of the roof and you have a minimum of 2.2 metres, then the loft can be converted. If the measurement is less than 2.2 metres even though the regulation on height has been relaxed in loft conversions, it is unlikely to have enough useable headroom clearance.

What insurances do you have and do you guarantee the work you do?

We have Employer’s Liability Insurance of £10,000,000 and individual Public Liability Insurance of £1,000,000. Both are available on request. We also offer a 10 year structural guarantee against our loft conversions and a 1 year free maintenance guarantee.

Fact 1  NOT all loft conversions require planning.
Fact 2  All loft conversions DO require Building Control approval.
Fact 3 Loft conversions ADD to the value of the property.
Fact 4 You DON’T need to move out of your property whilst having your loft converted