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Interior renovation of old buildings: the cost

Historic, old building refurbishments are usually more costly than typical house renovations. There are challenging requirements, regulations you need to follow, plus limitations and difficulties that you will face on the way to achieving the desired results.     Managing such a building refurbishment without having expensive failures requires years of experience. For the last 15 years we have been renovating the most luxurious London properties, so we are in a position to provide you with some important tips to consider.    In this article we present some hurdles you might meet during the renovation of old buildings, and how they may affect the final costs. We will also show you how much these costs might sum up to, based on London prices. 
Cadogan Square grade listed victoria building - luxury maisonette refurbishment

Regulations vs. renovation of old buildings

To manage the project you need to pass obligatory regulations imposed by the relevant council and, in Grade listed buildings, English Heritage. In addition, apartments located in mansion blocks are affected by rules set out by building management companies. In those, you would typically need to apply for a licence to alter anything.

Such building management requirements may also exist in relation to the ways of operating within the building, goods in and out, hours of working, and noise limitations. Also, certain methods of sound insulation, fire protection, or leak detection systems must be used in certain locations.

Let us guide you through the most cost-generating areas:

#1 Sound insulation

Some lease agreements may include an obligation to install soundproofing systems before wooden floor installation. This forces you to lay carpet again if the requirements are not met. 


All acoustic works require hiring an acoustic engineer who will carry out measurements of airborne and impact noise values between apartments, in both existing property conditions and after completion of the works.


Average additional costs: 

  • from £150 per sqm for professional soundproofing installation, subject to the system used and its complexity,

levelling and substrate replacement to the entire floor is often required, which is a completely additional cost from £130 per sqm.

Hilton London Paddington - Facade of the building

#2 Fire prevention systems

– the price of building renovations in mansion blocks also increases because of additional fire regulations. For example, it may be necessary to install fire sprinkler systems.


Average additional costs:

  • From £7,000 per installation, depending on the size and extent of the system.

#3 Site access restrictions

Some building  management companies don’t allow use of main building staircases in mansion blocks. The same problem may occur during a house or an apartment conversion. As a result, the builders will be forced to move materials through narrow fire escape routes if that is an alternative. As a consequence, you will need to hire more labourers to assist, which will increase the overall costs of the work.  


Sometimes you might even have no access at all, so you will need to set up scaffolding and install a hoist to transport materials and waste. For example, we encountered this situation while renovating a flooded apartment in Belgravia. 


Average additional costs:  

  • at small sites, setting up scaffolding and a hoist together with security of the space around them can cost an initial £2,000 plus a weekly hire fee of £400 thereafter,
  • large construction sites with dedicated lifts certified for moving personnel and materials can cost upwards of £10,000.
RAC club Pall Mall, London - facade of the building

#4 Additional fees

Building managers can request a deposit, in the form of a £10,000 payment to a bank account for covering potential damages during the project. 


They may also expect you to pay their surveyor, who will inspect the works on a regular basis. Sometimes you have to bear the costs of weekly photographic documentation needed for tracking renovation progress across the entire site. 


Average additional costs:  

  • a surveyor costs from £250 per meeting, 
  • photographic reporting costs from £150 per week. 

Building renovation surprises

Old buildings can surprise you in terms of their mysterious past, or undocumented alterations and elements that you need to rebuild or rectify from the beginning.

#1 Hidden secrets

Sometimes you only find out what’s behind the walls, floor or ceiling during the project. To visualize this scenario, we will use one example from GBG Building Services’ previous work.  


In one building, we uncovered triple individual suspended ceilings, and when we reached the original ceiling from the 1800s, we also discovered a labyrinth of gas and communal heating pipes servicing upper flats. That came as a surprise and it involved a lot of people to manage the process. It required informing and dealing with all owners and tenants on an individual basis. At the same time we were carefully re-routing the services away from our clients’ apartment. The entire process delayed the planned site work in those areas by 2 months. 


Average additional costs: 

  • removing additional suspended ceilings including extra rubble removal costs from £100 per metre,
  • re-routing communal gas and central heating in various rooms costs from £3,000 per location.

#2 Old materials and building methods

Sometimes a project requires the replacement of previously applied materials or building methods. The reason behind this is to ensure safety. Let’s use another example from our work to demonstrate some possible changes. 


During one of our projects, we had to open up the space and install three structural beams. Everything was calculated to rest on padstones on side walls. It turned out that in the designated position of some supports was an old undocumented chimney stack from the 1800s with crumbling brickwork. This element, together with the walls, had to be carefully dismantled down to the ground floor and rebuilt. This enabled us to carry the weight of the new steel supports. 


  • Average additional costs from £4,000 for unexpected structural changes.

Our recommendations on renovation costs 

When you embark upon renovating an old house or an apartment you need to be prepared for additional costs by having access to contingency funds, typically amounting to 10-15% of the estimated price, or more depending on the known property condition.


On average we advise our clients to set aside total construction budgets for renovating London-based properties of between £1,500 to £3,500 plus per sqm for mid-range to higher-end finishes and bespoke furniture. 


For example, the average refurbishment of an apartment of 120 sqm may cost from £180k to £420k plus, which also depends on any difficulties and restrictions you may meet on the way. 


Old buildings can surprise even the most trusted and reliable builders, should they not identify those possible problems from the start and allocate suitable PC sums. The truth is that additional costs won’t simply disappear if you ignore them, so it’s better to be aware and be properly prepared.


If you need any help with surveying and estimating your project, feel free to send us your request. 

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