As with any major building project, you will need to match up your budget to the design. This initial phase will take a while to get right. Even though the space you have might seem small in comparison to the rest of the house, the design will need to pack a punch to make a real difference to the way you live.
For example if you’re adding a kitchen would you like it to be exposed to the morning sun? Then it needs to face the eastern elevation. And don’t forget to take into account the context of the site, including prevailing winds (which will help position vents to avoid them), and connection to existing house.
To help you design the extension and put it to paper, you’ll therefore need an architectural designer. Check references and insurance, and make sure you like their style and speak to previous clients to make up your mind which architectural designer is the right one for you.
The architectural designer can stay on during the construction phase and this is a wise decision because they will be able to check progress on site and act as a liaison with your builder. Some self-builders hire an engineer to carry out this technical role instead.
You may need a structural engineer at the design stage too for things like specifying steel. In all likelihood you will also need to hire a building energy assessor.
You may or may not need to get planning permission but in all cases, let your neighbours know what you’re up to as early as you can – ideally at the dreaming stage. It’s common courtesy and they may have information about your house or site that could be interesting to know.
The design will be developed in parallel with your budget; the best place to start is to get an idea of how much you have to spend by checking finances are in place and assessing how much you will realistically need with design fees, planning fees, insurance and warranties.
At this stage check whether your house insurance is still valid during construction and whether it can be extended to site insurance during the works. Bear in mind if you hire a contractor to take on the project management, check that their insurance covers all the necessary for your site, most importantly public liability but also employer’s liability.
After that you will need to consider if the extension will require an upgrade to the existing house, e.g. you may need to upgrade your heating system if it’s already working at full capacity, floors in the existing house may need to be replaced to match and line up with the extension, etc.
The site itself may present challenges and added costs. For example if access is difficult (imagine having to transport concrete in wheel barrows through the front of the house instead of having it all delivered where it needs to be) or if you need to upgrade your onsite wastewater treatment system as a likely condition of planning permission.
To save on costs have a look at which windows, doors, kitchen, tiles or other relevant products you will need to source yourself. It takes a long time to find what you want and at the right price – knowing this in advance will help the design process immensely, and will assist in the costings. By getting detailed construction drawings done you’ll be able to accurately price your project – you need a detailed specification otherwise costs are likely to creep up.
Also very important to bear in mind are the changes to the building regulations in ROI. If you renovate 25 per cent or more of your home you will have to upgrade the entire house to bring it up to a B2 Building Energy Rating which will in all likelihood mean, at the minimum, adding a considerable amount of insulation.
How much you have for the actual extension will then become clear and the design will have to be tailored to it. If you can, set aside some money not only for a contingency but also for the landscaping. Once the extension is built, making the garden look nice will fast become a priority.
You don’t necessarily have to get planning permission to extend your home but you need to tick all the boxes to qualify for an exemption. There are restrictions on floor area (in ROI less than 40sqm), eaves height (in NI no more than 3m high), etc. If you have any doubt, ask for a Section 5 Declaration from your local authority (ROI) or a Certificate of Lawful Development (NI) to make sure your plans don’t require planning permission.
After that, there are the building regulations which include building control. The building regulations have to be followed for renovations; check the technical guidance documents and technical booklets, and consult with your building professional for advice.
If you secured planning permission you will need to go through the building control process by filing a commencement notice (ROI) on the Building Control Management System as you would for a new build.
In NI even if the work is exempt from planning permission you still need to advise Building Control, e.g. in the case of a roof space conversion or to install a wc under the stairs. All structural work must be filed with Building Control, also insulation work.
Exemptions include porches of 5sqm or less at ground level that protect an external access (but the glazing must comply with Part V of the Regulations), conservatories 30 sqm or less that have at least 75 per cent of the roof and 50 per cent of the external wall made of translucent material, and detached garages that are 30sqm or less and are either built substantially of non-combustible material or are not less than one metre from a dwelling or boundary of the site or a road.
If the project lasts more than 30 days or poses a significant risk, you must advise the health and safety authority (HSA in ROI and HSENI in NI) and appoint health and safety supervisors for both the design and construction stages. This work involves keeping a health and safety ledger on site.
Health and safety includes your builder checking in advance if digging is safe, checking for buried utility lines, and erecting scaffolding to best practice standards.