calculating your build costs
A simple cost estimating guide for people building their own home
one of the most important aspects when planning your self-build or home renovation/extension project is working out how much it is going to cost. This figure will depend on the size and shape of the house, the level of your own involvement, where in the country you intend to build, and the materials you’re going to use. If you can make even rough decisions about these factors, then you can begin to
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work out how much it is going to cost.
As a very general rule of thumb, expect a building plot to cost between a third and a half of the end value of the finished house. The costs of building a house will then depend on the variables listed above. All building work is usually quoted on a cost/m2 basis. For example, a typical new four bedroom self-built home is around 200m2 (with 100m2 on two sto-
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reys) and usually varies between £1,000-£2,000/m2 (although self-builders can achieve costs of between £300-£3,500/m2).
Renovation costs are more difficult to establish as they involve many variables, but allow at least £1,000-£1,500/m2 for work. This, added to the cost of the plot/house and with a 10-30% contingency, should result in less than the final end value of the house.
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The table below, based on information from the Building Cost Information Service (part of RICS, the Royal Institution of Chartered Surveyors), is updated monthly to help you work out a more accurate estimate (note, however, that these figures are for build costs only and do not account for VAT, which is not charged for self-build projects). There is a free online version at homebuilding. co.uk/calculator.
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1591 1913
1448 1740
1384 1664
1742 2263
1527 1985
1390 1807
1329 1728
1469 1844
1279 1605
rainfall varies hugely in the UK and we have less available water per person than most other european countries*. as a result, water efficiency requirements are included in the Building Regulations for all new homes, including conversions.
The Regs (Requirement G2 england and Wales) set performance targets for maximum water consumption in litres, per person, per day (indoor swimming pools, saunas and Ja-
cuzzis are exempt).
The Regs set a national maximum of 125 litres per person per day (or l/p/d) for compliance. You will need to submit either the schedule of fittings or the design water calculations as part of Building Regulations plans prior to starting on site. If any details have changed during the build, you will also have to submit ‘as built’ figures on completion.
Local authorities in waterstressed areas can also impose a more onerous standard of 110 litres per person per day. They do
of water can be wasted every day and around £300 a year added to water bills if left unfixed!
The Green Building Store recommends designing out this problem with the use of siphon flush toilets – the staple of British plumbing before 1999 – as they are inherently leak free. Water-saving versions of the siphon flushing Wcs are available, including Green Building Store’s eS4 Wc.
sinks and Basins Kitchen and utility room taps often require some decent pressure for washing up and it is usually best to avoid cutting the pressure down too much here. Hand basin taps, particularly those fitted to small space-saving basins in cloakrooms or en suite bathrooms, can comfortably take low pressure. (Indeed it makes perfect sense to fit them to these small basins, otherwise a strong jet of water could ricochet out of the bowl towards the ceiling — or you.) If there is anywhere in your water consumption design for reduced water use, this is the place to do it or at least to begin, but as a guide, flow rates on these taps are commonly three litres per minute.
If you struggle to find the required flow rate for your choice of taps, you’ll need to fit pre-set flow restrictor valves to the supply pipes beneath the appliance. These valves are colour coded to set flow rates and can be fitted on the appliance side of any valve, riser or shower hose as required. Baths The taps are irrelevant on baths. This is all about the
volume of the bath. a standard (1,700mm long) bath usually has a capacity of about 170 litres, but shorter baths are available with a capacity of around 140 litres or less if you are tight on space or need to conserve water.
Larger bespoke baths are popular for those wanting to make a statement or indulge in some luxury. However, apart from increasing your water consumption, they have another unexpected problem: given the time it takes to fill them, hot water may cool before the bath is full and ready for you to get in.
showers Far more water efficient than bathing, showering is also more time efficient. However, there are some amazing showers on the market that can recreate a tropical deluge or direct water jets to massage as well as cleanse you. These power experience showers have a high water demand and are capable of fouling the maximum water consumption requirement quite enthusiastically.
at the same time, residents that have very low shower flow fittings installed are commonly disappointed by a shower that all but dribbles on them. Trying to find an acceptable balance is the trick and most of the water calculations I see come in between 8 and 10 litres/min flow rate for the shower achieved by a flow restrictor insert valve.
Appliances The actual figures from appliances fitted on completion should be entered and these are avail-
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ton. “A good designer is also a good listener and they will have flair, creativity and experience. Ask to see references and examples of the designer’s work, know their track record of planning approvals and ensure that they have a thorough understanding of the planning system.”
Before approaching a professional, you will need to know what your priorities are for your new home and come up with a brief. Make sure, as well, that your designer returns final drawings that are achievable within your budget.
get Approval
Planning can seem like a complicated beast – lessened somewhat if you find a plot that has planning permission already granted on it perhaps – but it’s about understanding the situation within the context of where you want to build.
You should receive an answer within eight weeks of submitting your appli-
cation, but be sure to keep track of your application.
Receiving approval is not the end of your relationship with the planning officer. All planning permissions are granted with conditions attached. These can range from specifying what type of roof materials must be used to the date the project must start by.
Failure to address the conditions will invalidate your consent, making any work done illegal. Conditions must be formally discharged (or satisfied) in writing, usually through a form obtained through your local authority — and with a fee attached, of course.
You’ll also need to submit detailed building drawings for Building Regulations’ approval (or a Building Warrant in Scotland). Building Regs are national legal standards for design and construction that apply to all new builds. The assessment on whether your build will gain approval can either be carried out by your local authority’s building control team, or you can appoint a private approved inspector.
You may also be able to sort your structural warranty through an approved inspector, which may save some costs.
go out to tender
Much like finding a designer, choosing a builder requires plenty of research on your part. Ask your designer, friends, building control, neighbours and anyone else you know who’s had building work done for recommendations.
Meet and interview as many as you can and ask them to quote on your project based on tender documents that your designer may have helped you to prepare.
Sort your insurance
As soon as contracts are exchanged on your plot, you will need to have insurance — usually a specialist policy for self-builders. A compre- hensive self-build policy is advised. The policy will cover public liability, building works, employers’ liability and personal accident.
Arrange for Services Getting services to your site (if necessary) can cost between £500 and £10,000+, depending on your situation and whether the connection needs to be made across private land (where you’ll need to secure a wayleave to grant access to dig) or public highways (which may involve road digs). Though electricity and gas are not essentials during the build, a water supply is needed early on.
Turn to page 176 for our self-build schedule so you know what to expect during the build process.
turn over for a beginner’s guide to health and safety on site
how Could render Improve My home?
QWe have a run-down brick house in need of a little TLC and we’re considering recladding the building in white render to give the house more kerb appeal — other homes on the street have done this and it looks great. What render should we use?
aMIChael holMes saYs:
Render is an exterior wall finish that can be smooth or finely textured. It can be given a contemporary finish with sharp edges by using metal beading, or a softer, organic look, more suited to vernacular buildings, with hand-formed rounded edges.
It can also be finished to look like smooth coursed stone by moulding joint lines into the top coat — also known as stucco. Wet cast, wet dash, pebbledash and roughcast (called harling in Scotland), are also types of render. It is usually applied to improve a building’s weatherproofing and add aesthetic appeal.
The main types of render you’ll find include traditional lime, cement and monocouche. The type you choose will depend on your home’s construction, your budget, maintenance requirements and the aesthetic.
Traditional render is made with lime and washed sand, and may be reinforced with clean animal hair or other fibrous material to prevent cracking. For traditional solid-walled buildings (i.e. those without a cavity, typically built pre-1920s), it is important to use a limebased render. Its flexibility and self-healing
QMy wife and I are undertaking a major renovation and extension project of a house which has fallen into a state of disrepair. We’ve been told that due to the scale of the work involved we will need to apply for planning permission, but as first-timers, we are unsure as to what to expect when going through this process. Can you offer any guidance?
ajason orMe saYs:
The first thing you need to know is where and how to apply. For significant extension and remodelling projects, you can apply either through your local authority or online through the Planning Portal (planningportal.gov.uk). Anyone can apply for planning permission but in most cases it’s either you, the homeowner, or a designer who will manage the application. It will cost £206 to submit an application in England, £190 in Wales and £202 in Scotland. (Visit your local authority’s website for pricing in Northern Ireland.)
In order to decide whether your proposal has a realistic chance of success, you should consider engaging the local authority in pre-application advice. This is, in many ways, ‘planning permission-lite’, requiring the submission of a sketched scheme, forms and written documents to outline your intentions. local authorities vary in their approach to this, with some charging between £100 and £200, while others offer it for free.
Their response will give you a good, but non-binding, indication as to your scheme’s chances of success and if it needs amending before submission.
Your pre-application advice will highlight any special reports that you may need to compile, such as an ecological survey. However, in the majority of cases, you will have to submit an application form, an ownership certificate, a location plan, before and after elevations and floorplans as part of your planning application. The strict criteria will be listed in your local authority’s validation requirements, which can be found online.
You will probably also have to submit a design and access statement, explaining the thinking behind the proposed scheme and justification for it. Here, it’s worth studying local policies and making a note of what the planners look for in terms of size, scale and materials — tailoring this into your scheme will pay dividends.
Once submitted, your local authority’s planning department will validate the application to check all the required documentation and fees have been supplied, for which you’ll receive a confirmation. local authorities have a target to respond to planning applications within eight weeks of receipt, so around 90% of decisions are made within this time. During this period, statutory consultees are notified, including the highways department, parish council and your neighbours, and invited to respond if they are unhappy with the proposals.
generally, most planning decisions are made in one of two ways: either by the local planning committee if the proposal is particularly controversial, usually in the case of new houses or housing developments, or, in the case of most householder projects, delegated to a planning officer to decide.
If you’re lucky to receive an approval for your plans, be sure to make note of the planning conditions attached, as
they are just as important. Most approved applications come with notes, such as requiring the local authority to approve the exterior materials before commencement of work, or perhaps having sign off on a landscaping scheme. You will need to formally apply to discharge these conditions and receive a letter to confirm so, as failure to do this will invalidate your planning approval.
You may need to tweak your design after gaining approval, for which you have two options: either use the minor amendments route, which is designed for issues like new window positions, or submit a new planning application.
The minor amendment route costs £34 and takes 28 days to decide, while another full planning application would take eight weeks but is free if applied for within a year of the original.
If the news is not so good and permission has not been granted, look carefully at the reasons given for the rejection. If it is because your scheme is in breach of local planning policy, then you will need to redraw it. If you don’t believe it is, you will have a more serious case for appealing the decision.
In either instance, a conversation with a planning consultant (see rtpiconsultants.co.uk) is probably a wise course of action.