Planning and budgeting

Building companies are dealing with rising costs – of materials, fuel and staff – which, in turn, are being passed on to those of us wanting to make big changes to our properties. An average increase of 20% from 2022 to 2023 underscores the importance of having a clear idea of how much your renovation project will cost from the outset. As always, a contingency fund is advisable. If unforeseen expenses arise, this can keep things from grinding to an untimely halt.

If you’re in the market for a mortgage, listen to our discussion on the best mortgage deals available right now at both fixed and variable rates.

Budgeting – five top tips 

1. Start with a plan of exactly want you want to achieve. Changing plans once work is underway is almost always costly as well as disruptive. 

2. Contact at least three tradespeople for quotes.

3. Read the details of the quotes and be sure that you are comparing like with like. Ask each one what they will supply and what you will need to provide.
4. See if there are any products and materials that could be substituted for cheaper ones.
5. Add at least 10% to the estimate as a contingency fund.

Planning permission

If you want to build something new, make a substantial change or addition to a building or change its use, you may need planning permission. If this paperwork is not in place before work starts you could be landed with a hefty fee or asked to undo the work. It could even saddle you with a criminal record.

Some projects come under ‘permitted development’, which means they don’t require planning permission. Examples can include extensions and conservatories, garages, sheds, paving over the front garden, installing windows and doors, adding a skylight and building a wall. However, always err on the side of caution, as there are exceptions to these general rules, such as:

• Building extensions that are more than three metres long
• Using materials that are radically different to those in the existing house/property
• Your home is terraced or has already been extended
• An extension that isn't at ground level
• The volume of your house will be increased by more than 15% or 70 cubic metres, whichever is greater.

There are also more controls if your property is listed, or if you live in a conservation area, national park or designated Area of Outstanding Natural Beauty (AONB). You should contact your local planning authority or visit the Planning Portal to learn about any extra restrictions.

You can get more guidance from our Which? Trusted Traders on when to apply for planning permission. 

Not sure whether to renovate, extend or put the house on the market? Our Moving and Improving hub has you covered. Listen to the Which? money podcast for answers to the big property questions of 2023.

Building regulations

Quality of materials, dimensions of rooms, fire safety and much more are covered by building regulations. These rules exist to set legal minimum standards for the design, construction and alteration of buildings. 

An extension or alteration to your property, plus any new building, will need to comply with building regulations. At the end of your project, you or your builder will need the sign off from building control to certify that it reaches the acceptable standards. 

At least five weeks before you start any work you should contact building control at your local council if you’re doing any ‘notifiable work’. This means any new construction or extension of a building, but it can also include replacing fuse boxes, insertion of insulation into a cavity wall or adding extra radiators to a heating system.

Building regulations vary between countries. Find out what you’re obliged to do according to where you live:

• England and Wales
• Scotland 
• Northern Ireland

Our Trusted Traders site offers more advice on building regulations. 

Electrical regulations

Dodgy electrics can cause serious issues, including fires, which is why certain electrical work counts as ‘notifiable.’ Examples of these are installing a new consumer unit, installing or altering a circuit, plus full and partial rewiring. 

Technically, you can use an unregistered electrician, builder or handyman to carry out notifiable electric work, but it might not be worth the shortcut. The work will still need to be signed off by either building control or a registered electrician. If you use a registered electrician for the work in the first place, they can self-certify the work they do.

We strongly recommend using a registered electrician for all electrical work, whether it’s notifiable or not. They will issue you with a Building Regulations Compliance certificate.

If you don’t use a registered electrician for notifiable work, you must tell building control before the work begins. You will need to pay an extra fee for someone to come and inspect the work before you do anything. They will issue you with an electrical inspection condition report (EICR). This is not equivalent to an installation certificate – and to get one of these, the work would need to be completely redone by a registered electrician.

Not having the certificate can become a problem when you want to sell the property. The buyer’s solicitor will likely ask to see it as part of the house sale. If you haven’t got one, it will hold things up and, in some cases, could even prevent the sale from progressing.

All electricians endorsed by Which? Trusted Traders have the necessary qualifications and membership to self-certify their work. Use our easy search tool to find a Which? Trusted Traders-endorsed registered electrician in your local area.