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What’s The Cost Of A Single Storey Rear Extension In 2023?

What's The Cost Of A Single Storey Rear Extension In 2023?

Are you looking for more space in your home? Think that a single storey rear extension would give you that dream kitchen or the space for the larger sofa but not sure what this will cost you and what you should budget for at the outset?

This post runs through what the cost of a single storey rear extension is in London in 2023.

Realistically, as with all things cost related a lot of this will be dependent on size and finishes and the extent of other work that you are looking to do. You may want to invest in more expensive final fixtures such as kitchen as you acknowledge that this is a home for life equally you may know that you like change and may want to rip out the kitchen in a few years in which case you may not want to spend on a kitchen from a High Street boutique kitchen showroom – both could impact the final cost of the works by £10,000s!

So where to start in that case; we always like to understand what you would be comfortable spending. It is important that you take the time to understand what this comfort level is; it will be different for everyone and the level of investment that you are prepared to make is unique to you. So as a starter ask yourself:

  1. How long do you envisage yourself living in the property?
  2. What will the impact to you and your family if this work was done – is it going to result in better family harmony at breakfast time for example which may lead to a better start for you and your partner to the day?
  3. Are you going to need to borrow money through a remortgage to support the works and if so; how does this make you feel? When thinking about this, think about how any changes in interest rates may also impact you in the future and when your mortgage may expire relative to when you may be looking to retire/ change income levels.
  4. Is this work something that you are only likely to do once in your lifetime?
  5. What will happen as your circumstances change – for example when the children flee the nest? Will the space be redundant or will there be ongoing value to your lifestyles?
  6. How would the perfect kitchen/ dream living space make you feel and what price is that feeling worth to you?
  7. How flexible do you need the space to be; both in the short and long term?

As you can see, some of these considerations are practical, some are also emotive and centre around improving quality of life which often a true value cannot be put on – although if it leads to a greater connection as a family if you have a lovely dining space where you can sit and congregate this may be priceless.

You may also want to reflect on the fact that if you invested the money in the extension and circumstances changed and you needed to sell would you feel aggrieved if you could not recover the return at that point?

Often, this may not be possible, particularly outside of London given the current high cost of building works, so you need to mindful of this as investment may not always be financial.

So, now you hopefully have a figure in mind as to what you are comfortable spending. So then how much will it actually cost? Typically, in 2023 the square metre cost of an extension in London currently comes in at £3500 – 4000 per square metre.

Within this you should then consider the points above about what other work do you need to undertake as part of this project – often a single storey rear extension results in creep to other areas such as changes to other parts of the ground floor; moving of services, new underfloor heating and things like a new downstairs WC – so now the project is not just an extension to the ground floor but a full refurbishment of the ground floor and this is where it can be harder to outline costs for the overall works using square metre rates.

Ironically, a very small extension is likely to cost more than a typical 20sq.m extension. This is due to the associated cost of materials and spread of this in a small space and labour for this.

If there are constraints accessing the site this will also increase the costs. So if you have parking restrictions, you may find that the cost of the builder obtaining permits from the council to park is higher than you providing them permits – you may find that this over the course of the extension can cost thousands when you consider the cost of parking in some parts of London.

Although, in many instances this is an unavoidable cost, a sensible approach to it can save money that you can then spend on the inside. Equally if you have side access you may be able to get a small digger down to dig foundations, which could be quicker than doing this manually and taking muck away through the house which is limited relative to the access.

The cost of putting a skip on the street versus being able to accommodate this on the drive all can have small impacts on the cost of the works.

To determine an accurate cost for the works, we would suggest preparing a detailed set of construction drawings that consider all the details, from any final finishes through to lightings and electrics and where you can make any decisions at the outset – this avoids the need for lots of costly changes on site and potentially abortive works associated with this in the event that you change your mind.

And of course, it costs money at the outset to pre-determine all factors before works commence and this in itself is an investment but one that is likely to save you money in the long run. As you maybe able to appreciate the labour cost of moving things once they are done on site far outweighs the cost of defining what you want prior to works commencing – particularly since during the build you may feel pressured to give answers rapidly and without the ability to clearly think these through and not fully knowing what the cost is, notwithstanding the impact of any time costs on delay on matters and this may stretch to the cost of rental whilst your works is being undertaken.

Once you do have a set of detailed construction set of drawings clearly defining what is needed and who is to undertake it, it would be advisable to get 3-4 builders to price for the works. Be mindful that at the moment with so many cost fluctuations quotes may not be valid for long periods of time and the builder’s cost may caveat fluctuations in the rising cost of materials.

If this is the case you will want to allow for some form of contingency as what costs are in place now by the time the builder is undertaking the works in 3-4 months time the market cost of the raw material may have increased significantly.

We have discussed extensively the cost of the actual building works and what can impact these in 2023 – typically in addition to this, you will need planning and other statutory elements discharged and it would be advisable to budget circa 10-15% of the build cost for consultant fees. You can read more about what to expect to pay for consultants in one of the articles on this in the learning hub.

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