_ Typical styles of house extension plans and granny annex designs _
Single storey house extensions
Most house extensions tend to be single storey designs, projecting from the rear of the existing house. These type of extensions are used to form additional living rooms and often combined with kitchens creating open plan kitchen, dining , living room extensions.
Other more simple single storey extension designs are side extensions, often designed to form utility rooms, ground floor toilet facilities, garages and sometimes to knock through into the existing house to enlarge an existing room.
Single storey extension plans do sometimes project to the front of the house, these often forming entrance halls, toilet facilities or to enlarge existing front rooms.
Front, side and rear extension plans are often combined to form wrap around extensions. With clever engineering it is possible to remove whole corners of the existing homes to open the house out into the extensions creating vast open plan living spaces.
In many cases side and rear extensions can be built without planning approval using permitted development rights. Front extensions with the exception of some porch designs will most likely require planning approval.
Two storey house extensions
Plans for two storey house extensions are popular when a client requires an extra bedroom or to simply better proportion the sizes of the existing bedrooms within their house. Often the ground floor part of the extension is used to contain a ground floor WC, a bigger kitchen and sometimes an improved living room.
Double storey extensions are very often combined with single storey extensions to gain the best possible use of space without the expense of a full double storey extension and sometimes the extension is designed to consider the circulation required to access a loft conversion.
In most cases a double storey extension will require planning approval however under certain circumstances the plans can be kept within the parameters of permitted development.
On many modern style houses, 2 storey extension plans can incorporate an existing side garage providing that the existing foundations have been confirmed as suitable for the construction over. To support the first floor an amount of structural engineering is required, this however when properly considered should not be a reason to put the build out of budget.
Commonly known as a 'Granny Annex' these type of house extensions are ideally suited to accomadating extended family or giving independance to a family member who might be struggling phyically for financially while keeping them within the home evironment.
Sometimes after the immediate need for the annex has passed, the additional room is let out to help the home owner meet mortgage payments or just provide an extra income.
An annex while prodominently self contained must share facilities so as to remain as part of the dwelling. When planning permission is granted there will often be a condition attached which will ensure that the annex remains part of the original house and not sold as a separate dweling. Independant separate front doors and garden access are generally acceptable as are separate stairs for two storey designs. You could meter gas, electric and water to the annex and the original house separately and provide independant heating systems, however providing services separately can add cost to the overall proposal.
When considering the design of a house extension there are several things which need to be considered
1. Are you creating any additional bedrooms? If so will there be enough parking spaces to meet with the local authority parking standards.
2. Has the design identified foul drainage? Access to existing foul drainage is important for connecting new bathrooms, en-suites, kitchens and utility rooms. Although there are mechanical methods to deal with foul waste, gravity systems are the best solution when it comes to low noise and maintenance. Also, where are the external foul drain pipes? Does the design run over the top of a shared drain? There are solutions to these constraints in many cases however permission must be sought to build an extension over shared drains and the design needs to incorporate inspection chambers to enable rodding of the pipes.
3. Will the design affect the underground services such as electric, gas and phone? Relocating these services while generally possible can be expensive and so, unless you really need to move them to achieve the design you want, they are best left alone.
4. Trees will affect the construction of the extension and in some cases trees are protected, requiring permission to remove them or carry out any significant pruning. Root protection zones and method statements are generally required at planning stage to document how the trees will be protected during construction. The effects of tree roots can affect how deep footings are cast subject to the building inspectors approval.
5. Access is an often over looked part of the design. Building right to the boundary might be your only solution to achieving the space you want, however if this blocks the access, say from the front of the property to the rear and there is no other access routes, consideration should be given to how you would move items such as gardening equipment, bins etc from the rear of the house to the street. It might be that the only route is straight through the house meaning you will need to be prepared for the resulting mess.
Access into an extension of the house internally can often be an afterthought if not considered early on in the design. Long hallways and dog leg routes can make a house feel unconfortable and claustorphobic. Taking disproportionate amounts of space from existing bedrooms to achieve the goal of access might make result in the extension being a pointless excersise if your plan was to create more bedrooms.
6. Heating and energy saving systems are worth considering early in the design. The fabric of the building needs to be built to a high standard in the first instance, then which ever heating system you install, you will get the best possible performance. If you are constructing an extensive ground floor extension you should consider heating the ground floor area with a wet under floor heating system. This is far more efficienet than radiators although the install cost can be higher. Small extensions on the other hand might be better heated with a simple under floor electric system backed up with a radiator. Electric heating elements are easy and cheap to install, but not as efficient as a wet heating system. Once the floor is warm it will stay at a fairly even temperature with fairly minimal input. If however the budget it tight and you don't mind radiators then this is the cheapest to install in most cases however they are not as efficient due to the way they heat the room.
New windows and doors will conserve heat however they tend to be air tight. This is a good thing generally however consideration should be given to air handling systems to remove air bourne moisture which will condensate and could result in mould growth. Trickle vents installed in the windows provides some back ground ventilation however they aren't perfect so mechanical ventilation is the next step. The most efficeient air handling system being whole house heat recovery which handles extraction and replacement air, however this type of system can be difficult to install as part of an extension due to the ducting required. A low cost and easy to install solution is a positive input ventilation system which ensures that there is a regular change of air and forcing out stale air within the extension and the existing house. Couple this with standard extract vents and the likely hood of your newly renovated home going mouldy will be significantly reduced.
7. The extension designs can have an impact on the neighboring properties in serveral ways. Loss of light and outlook needs to be considered. Most councils will consider a 45degree splay from the extension to the neighboring windows as a general rule of thumb. When required a more detailed sun shadow study should be generated to show the shadow fall from the extension and how it affects the neighbours.
The party wall act is not optional and so advice needs to be sought before any building work comenses to ensure all the appropriate notices and awards are in place before work commences. A pre-commencement condition survey by an independant party is strongly recommended to document the condition of the adjoining owners property.