How much do loft conversions cost?

This is one of the most frequently asked questions we get asked here at Home Tales. House renovations in London can be expensive, however if done properly you should more than make you money back on the value that is added to the property. This means you not only gain the money back, plus some profit, but you also get the benefit of more space. 

In a survey done by ‘on the market’, they estimated that loft conversions that include one bedroom and en-suite add around 21% to a property’s value. In London, where space is even more valuable, this has been noted to be around 24%. Let’s take an example to put things into context. Let’s take a typical London property, and value is at £1m. This means adding a loft conversion would add between £200,000 and £250,000 to the property’s value, making it £1.2m to £1.25m. 

You can expect a loft conversion to cost between £25k to £60k in London. The main influence on cost will be based on three factors. The first is the size of the extension you are proposing. The second is the glazing within that extension. What kind of windows, rooflights and doors do you want? The last factor is the host properties structure and layout. For example, if the ridge height of the property is low, you might need to drop the first-floor ceiling to gain an acceptable head height in the loft. 

We thought we would talk you through some of the most popular loft conversion designs and the associated costs. 

Design and pre-site fees 

To undertake a loft conversion, you will need to gather a variety of items before you can get a builder to start the works. The first is architectural drawings. These are floorplans which show the measurements and layout of your existing property, including sectional details and elevations. You will then develop a design with your architect for your loft conversion design. Once you have a final design, you will need to apply for planning permission from your local council. If your design fits within the criteria of permitted development, you will still need to apply for a permitted development certificate. This confirms the council has reviewed your proposal and they agree it fits within the realms of permitted development. Once you have gained the necessary approvals via your council, you will need structural drawings. These are completed by a structural engineer and can generally be arranged by your architect. Here at Home Tales, we offer a design bundle which includes all three of these items. You can select them individually, but you ultimately need all three, so it makes sense them bundle them into our package and benefit from a cost saving as a result. A typical design bundle for a loft conversion will cost around £2.6 to 2.8k. 

You will likely need to consider party wall notice too. You are required by law to notify your neighbours that you are intending on carrying out building works. This can be done via a party wall surveyor. The fees range considerably depending on what your neighbour’s reaction is, and it can range from £0 to £2.5k per adjoining owner. 

You will need to appoint building control to oversee your build. You can do this via your local council or via an independent body. For a loft conversion, you can expect this to cost around £700 to £1500. 

Single dormer

For a single dormer, you can expect build quotes to be around £25k to £40k for a watertight shell. If you have a particularly wide property, it might be more. This is for the shell only, and you will need to factor in glazing and windows (see additional extras). 

L-shaped dormer 

A l-shaped dormer will cost around £35k to £55k for a watertight shell. A l-shaped dormer typically allows for two bedrooms to be added to a property, although in some cases homeowners might chose for the rear room to be a large family bathroom instead. Remember that with two rooms, comes an extra window or Juliet balcony. 

Additional extras

An aluminium window at 1m x 1m will cost around £1.5k. If you are incorporating an en-suite into the design, remember to factor in the cost of floor tiles and appliances. For example, a shower, loo and sink. If you want a Juliet balcony, this will set you back around £2.5k. Roof lights can be expensive and depending on the size you want you should expect £2.5k to £5k. They are also a pain to clean and require a professional, so factor this into your maintenance cost. Remember that you will need to carpet your loft, as all of the flooring is new. A typical 2-bedroom loft, with new stairs will start at around £1.5k to carpet with a reputable supplier (John Lewis). 

If you are thinking of extending your property, get in touch with our team today. We would love to learn more about your project and explain more about how we work. Did you know you can book a site visit via our online booking system? Get it confirmed within a few seconds. If you would rather email, send us a note to or call us on 0207 043 2378. 

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