Attic Conversion Costs and prices

Factors that affect the cost of an attic conversion

The style of your attic conversion, the size of the roof and the choice of internal accommodation are the three key influencers on the cost of an attic conversion. Estimates are divided in simple terms into labour and materials; the larger the roof and the more complicated the job the longer it will take, and the more materials you use will clearly have an impact on the final price.

Any attic conversion estimate you receive should have a detailed breakdown of the work including a very thorough and itemised description of all the materials. It’s easy to focus on the just the interior conversion but there are other cost factors to take into account:-

• Dormers and roof lights are ideal to flood the space with natural light but can be a considerable cost with the attendant work required on the roof structure to install them (read more about dormer window costs here).
• A staircase will be required from the top storey to gain access to the attic and this can require remodelling work depending on where it is sited
• Plumbing and heating will need to be extended and possibly re-routed so some people factor in a boiler upgrade. An extra bedroom won’t be too much strain on the household heating supply but a granny annexe or bedroom with ensuite could require some costly plumbing and heating alterations
• If your water tank is in the roof then it will need to be relocated and replaced with either a sealed system or an unvented system which removes the need for a header tank
• If you are opting for Velux windows, dormers or a mansard conversion then this will involve extensive work to the roof and many homeowners use this as an opportunity to refurbish their roof at the same time. Read more about Velux loft conversions here
• A traditional framed roof usually found in pre-1960s houses is the easiest and most suitable for loft conversions but the rafters might need to be reinforced or upgraded to bear the extra weight. Trussed roofs require greater structural adjustment and reinforcement as generally, they support less weight and this can impact significantly on cost
• Roofing material can alter the costings with slate roofs usually being pricier to alter than those with concrete tiles

Are there any other attic conversion cost factors?

In addition to the labour and materials, there are some additional costs which could include:-

• Hire charges – the cost of the scaffolding and crane hire if you are opting for a roof lift attic conversion
• Waste disposal charges – the charge for disposing of waste from the project which can be significant if you also choose to refurbish your roof or opt for a completely new roof on a roof lift conversion
• Professional fees – a surveyor or architect will be required to draw up your plans for the conversion and their fees typically average around £1,000 plus VAT. You may also need to pay the costs for a Party Wall Surveyor if your house is terraced or semi-detached and you need a Party Wall Award. Under the Party Wall Act of 1996, you are liable for the fees of your neighbour’s surveyor too if they choose to instruct one and you will also have to pay for any damage, remedial work or making good to their home as part of the construction project
• Surveys and consents – simple loft conversions do not need planning permission but there will be costs associated with a Buildings Inspector to conduct stage checks to ensure the construction complies with building regulations. These typically cost in the region of £400 to £800 and are organised through the local authority. More complex conversions that change the structure of the roof will certainly require planning permission as will an attic conversion in any house which is listed and/or in a conservation area. The fee for this is currently just over £170. If you live in a location where you have bats then you will need to pay for a Bat Survey which can cost anything up to £400. Bats are a protected species and any attic conversion has to be undertaken with this in mind

Why are homeowners adding attic conversions?

Converting redundant space in the roof is one of the most space-efficient and financially attractive options to create more room in your home; it avoids having to build an extension which is not always possible or desirable. No wonder so many people are doing it. Here are some of the many benefits:-

• Create more space without having to move house – moving is stressful, expensive and ultimately not very attractive in these current challenging times
• You might love your home and not want to move, the location is perfect and you have spent time and money decorating and refurbishing so your house is just how you want it, all you need is a little more room
• Attic conversions can help soak up the demands of an expanding family – create a home office or studio for a business, a cinema room for all the family freeing up a reception room downstairs for another purpose, a bedroom with en-suite or a granny annexe, the choices of how to use the space are almost endless and can have a huge impact on family life
• Loft conversions create the option of moving away from the standard style of accommodation in a Victorian or early 20th-century property and provide a blank canvas to create something open plan, original and contemporary whilst retaining the traditional styling in the main house
• Building extensions are not always possible or permitted at the back or side of your home or you may have already extended and still need more space. Extensions are expensive for the additional accommodation you can create and also require planning permission which a straightforward attic conversion may not, providing you are not altering the roof structure or live in a listed property
• If you have a valued garden or limited space at the back of your home, a rear or side extension will encroach on this whereas an attic conversion makes use of what is truly a redundant space
• Using modern Velux windows, even a straightforward attic conversion that doesn’t use dormer windows can create an incredible aspect to your new rooms which are just not possible with a rear extension. Open up stunning views of the cityscape or your rural surrounds with a real wow factor using roof windows that convert into balconies but sit flush with the roofline when closed or insert French windows into your Mansard attic conversion. The new accommodation will not just offer extra space but become a valuable design feature
• Attic conversions will increase the value of your home; Nationwide Building Society quotes a figure of 21% but some industry studies think this is on the conservative side and the real added value is even higher

What are the different types of attic conversion and the average cost of each?

Attic conversion costs will be very specific to the individual conversion, the size of the roof and the choice of interior fittings but it is possible to work on some average figures. Attic or loft conversions are broken down into different types:-

• Loft rooms – the simplest of conversions in a loft that already has sufficient headroom so a measurement of at least 2.2 metres or more when you calculate the distance from the bottom of the ridge timber to the top of the ceiling joist. Just add a staircase for access, any necessary reinforcements to the floor, roof lights to suit your interior styling and insulation plus final fitting and decoration. An average cost for this would be £15,000-£20,000 but much depends on the choice of interior design
• Dormer loft conversions – these are probably the most popular type of structural attic conversion. They extend outwards from the existing roof adding sections with vertical walls from the roof to create both ceiling height and floor space to the interior. They are very popular in Victorian terraced houses which tend to have lower attic voids than later properties and often limited space to extend at ground floor level. For what you can gain, a dormer loft conversion offers some of the best value for money and are priced on average between £30,000 and £60,000 depending on the final choice of internal fittings and the size of the conversion. A reasonable estimate would be somewhere in the region of £45,000
• Hip to gable conversions – a style which is appropriate for semi-detached and detached properties where the roof has at least three slanting sides. A single hip to gable conversion fills out one of the sides by adding a vertical end wall. A double hip to gable attic conversion just means building out on both sides. Hip to gable conversions are usually done on larger roofs and are more complicated which means they start at around £40,000 and can head northwards in excess of £60,00 with an average cost of around £55,000
• Mansard roof conversions – these are the most visually dramatic style of conversion and alter the entire structure of the roof adding a flat roof with sloping walls at an angle of 72 degrees. They can also have dormer windows. These create a vast amount of internal space but will significantly change the external aesthetic of the property. Of all current roof conversions, the Mansard is the most expensive starting at just shy of £50,000 and increasing to £70,000 on average. Read more about mansard roof conversion costs here. 
• Roof lift loft conversions – this is a route taken by some homeowners who don’t have the headroom to currently convert their attic into accommodation. The existing roof on the house is removed completely and replaced with a new one which is engineered off-site and lifted into position by a crane. The roof is constructed to perfectly create pre-planned room designs and can literally be swapped over in the course of a couple of days. The average cost will be somewhere in the region of £30,000-£50,000 depending on the usual variables such as the roof size, choice of internal accommodation and window styling

What are the stages involved in adding an attic conversion?

It is useful to understand how the works progress for an attic conversion but the costs typically will not be broken down in a staged way to mirror this. However, if the project is expensive and complicated, most homeowners will pay the roofing company or builder in stage payments as each section of the work is satisfactorily completed.

Here is the likely programme of works:-

• Drawing up plans – this is usually done by an architect or surveyor. The drawings will specify exactly what the final conversion will look like and incorporate all of the structural changes which need to be made
• Apply for planning permission – this is not necessary for all attic conversions, it depends on the scope and scale of the work. If you have a listed property or a house in a conservation area then you are almost certainly going to need planning permission even if your attic conversion is minimal and doesn’t outwardly change the external appearance of the property
• Building regulations compliance – irrespective of and independent of your planning status is the requirement for the work to be inspected to ensure it complies with building regulations. This is organised through the local authority. Building regulations cover things like floor strength and fire safety. The Buildings Inspector will not only want to look at the plans but also arrange staged on-site inspections as the work progresses
• Work commences – once the plans are approved and all the necessary consents are in place, then the work can begin. Usually, scaffolding is erected first to allow external access to the roof and sometimes a roof cover is used whilst windows are being fitted particularly if the weather is bad
• Access to the attic from the interior – this usually starts with the floor being strengthened and water and heating pipes re-routed if necessary. Then the dormers are constructed or roof lights fitted using a combination of working from within and from outside.
• Interior walls – these are fitted and insulated and the new staircase added. Electrics and plumbing are added followed by carpentry and plastering. The work is inspected for the final time before interior decoration and fitting take place