House Extension Types
Considering a House extension for your home? There is plenty to think about and plenty of ‘noise’ to get through. Here we are going to break it all down so you can formulate a solid plan for adding an extension to your home.
Ground Floor House Extensions
As the name suggests these are single storey extensions built at ground level, they tend to be less expensive yet cost more per square foot of useable space. Which, if you think about it is logical as every extension will need foundations and a roof for any given space.
Two Storey House Extensions
This style of house extension will have an upstairs. They will be more expensive to build than a single storey extension yet be less expensive than a ground floor only extension per square metre, because the additional cost will only be a floor and some additional height walls. As we said above all extensions will need foundations and a roof.
House Extension Design
Brick and Block built
Using traditional brick and block construction methods while providing a level of simplicity, are becoming outdated, materials have evolved to allow for greater efficiencies and in the right hands with the right guidance easier to build.
Timber Frame
Using conventional timber frame construction is one way to go when building your extension, this method of construction is relatively simple and widely understood by most traditional structural engineers. However, timber frame or ‘stick built’ has been surpassed in recent years by SIP construction which is a far easier method of construction.
SIPS
SIPS or to give them their full name ‘Structural Insulated Panels’ have been around for quite a long time, they are a superior method of construction yet not widely understood by the building community. SIPS are large format self supporting panels that have the insulation held between two sheets of OSB (Oriented Strand Board) is defined as an engineered wood-based panel consisting of strands of wood which are bonded together with a synthetic resin; the strands are pressed together in layers.
Pitched Roofs
Pitched roof or lean to designs can incorporate elements of glazing that are either fixed or opening similar to a Velux style roof light. They can have lightweight roof tiles or concrete style roof tiles to compliment your home.
Orangery Style Flat Roofs
Constructing an Orangery style roof with SIP panels allows the overall height of the roof to be lower. They also have the added advantage of being thermally superior to standard flat roofs of the same thickness. Glazed lanterns can easily be built into a SIP panel flat roof extension.
Doors and Windows
Wide expanses of glazing elements in your extension such as wide patio or BiFolding doors present certain challenges, one of which is the effect of glazing over the thermal properties of your extension. In simple terms glazing is less thermally efficient than walls. A SAP report will determine if your project can sustain being over glazed*. and wether or not it complies with the requirements to meet building control regulation. One clear advantage that SIP construction has over brick and block construction are the thermal properties of a SIP panel are far superior and can allow for more glazing as an offset.
*over glazed means that there is more glazing than the ‘notional’ extension regulations permit.
Planning Permission for House Extensions
The permitted development rights (PDR’s) planning rules in England are generally as follows
- A detached property can extend to the rear by 4m from the original back wall of the house.
- Any other property type can be extended by 3m.
- Side extensions can be a maximum of 50% of the width of the house.
The planning portal is a fantastic resource of current information regarding PDR’s and can be found by following this link It also explains the current rules for maximum heights.
Prior approval larger home extension scheme
The larger home extension scheme was originally discussed in 2012 as a temporary measure and while it had many alterations it was added into the permitted development rights act in 2019 as a permanent addition with some amendments from the original document.
The Larger home extension scheme allows for detached properties to be extended up to 8m from the original rear wall of the house and 6m for all other property types both of which have to have neighbourhood prior consultation and have a small proportionate fee attached.
Conservation areas and planning regulations
If you are in a conservation area, different rules apply, before commencing any project, ask your local planning authority (click this link to find your local planning authority). Ask before you start work as they have the power to enforce reinstatement and nobody wants the stress involved with that fight!
House Extension Cost
The simple answer is, they vary. The cost of a home extension depends on what you are looking for. The following costs are for an extension with a 4m x 3m footprint, that is 4m wide by 3m projection.
| Extension | £ Guide Price excluding VAT |
|---|---|
| Shell Only | £12,000 – £15,000 |
| Complete Build (not decorated) | £21,600 – £31,200 |
| Self Build Extension Kit | £13,200 – £15,700 |
| Self Build SIP only Kit | £5,830 |
Additional House Extension Costs
Please note all the guide prices below EXCLUDE VAT
Planning Fees
If you need to apply for planning permission then you will need to pay the fees levied by your local planning authority plus you will need some extension drawings done showing the before and after elevations. You could reasonably expect to pay £1,500 for a house extension architect to draw and submit the plans for you.
Building Control Registration
Typically expect £850 for building control registration and inspections. You will need these to provide a completion certificate at the end of your project so that when and if you come to sell your home all the paperwork will be in order.
Structural Engineering
You can budget £950 – £1650 for structural engineering fees, these will cover the technical aspects of the structure to the satisfaction of the building control inspector.
SAP Calculations
A SAP calculation will be required if you are looking to open the extension up to the main house, i.e remove the doors from the house to the extension. SAP calculations typically cost £225 – £475 and will be required by your building control inspector if you are opening the house up to the extension.
Foundations and Ground Work
If you are contemplating a self build you might consider employing a ground working company to get you out of the ground and up to DPC (damp proof course). You can do this yourself, but it is sometimes best to subcontract this task as ground workers tend to work well with building control inspectors and know what is required to meet their needs. Typical costs for groundworks up to DPC are £350 – £450 per square metre
Self Building and need some help with your Home Extension project
We offer a range of services and are specialists in SIP construction. We would be happy to help point you in the right direction, visit our contact-us page. Or if you would like to generate a guide price visit our SIP Extension Cost Instant Quote page and see an instant quote for your project.
However you choose to build your perfect Home Extension, we wish you the very best of luck and if we can help make the process easier and save you some money at the same time, then even better.
Some words from a customer…
Steve supplied my Sips Panel extension project and was brilliant from start to finish. He was very meticulous with planning and getting everything right for us just the way we wanted it.
It took all the stress out of the planning and design element of the project whilst also making me feel comfortable and secure with my purchase the whole time.
It all arrived exactly when and how he said it would and he even came to site to make sure everything was correct. It was also very useful that fixings and fittings and extras were supplied.
Everything went well with the build, which I completed alongside a carpenter. The Sips panel structure went up in three days which was brilliant and a great way to put up an extension.
Having lived in it for a few months now I can say that the insulative properties of the panels are great, they are very well made and all the windows and doors supplied have been very high quality which we are pleased with.
Overall we are very pleased with how the project went from start to finish, Steve and his company were great and it was a great way to put up a very secure and well insulated extension!”.
– Isaac, Oxfordshire