A house extension is often the most cost-effective way of creating more space for an expanding family. Moving to a new house can be expensive and a lack of local options makes this a daunting thought.
At Andrew Black Design, we excel in creating innovative solutions to problems with existing houses, whether it is re-configuring a poor layout or extending to create more usable space. From simple kitchen extensions to large glass sun-rooms, we can enhance even the humblest house.
We can take you from concept design stage, through planning and building approvals to helping with a trusted local builder.
How we design an extension
We advise our clients, except for the most basic of projects, to employ Andrew Black Design to carry out a full architect service from stages 0 to 5.
The services below (0-4) are generally the minimum you require from your Architect, to cover your legal responsibilities and are suitable for simpler projects for experienced clients only.
We offer a no-obligation, first consultation free of charge. We find it easiest to meet at the property or plot in question. This way, you can explain your hopes for the project and we can highlight opportunities and constraints and explain the process.
We will then send you an appointment letter, detailing our services, associated fees, other consultants required and the next steps.
Once our appointment has been agreed, we can move on to setting out your brief or wish-list. This will include your basic requirements, likes and dislikes, aspirations and budget. We prefer to spend as much time as required getting this right, as it influences the design process moving forward. We often find that it is helpful for clients to research the type of projects that inspire them, prior to starting the design process. This can make the process faster if the client knows what they like and, indeed, dislike.
At various stages throughout the project, you will need other consultants to support you in your project. Each project is different but a few of the typical ones are Structural Engineer, Quantity Surveyor, Aboriculturist’s (who deal with tree constraints), Flood Risk Assessors, Acoustic Consultant and Fire Consultant. We will advise you at the appropriate times which consultants are required and recommend suitably experienced ones.
If working on an existing property, we will carry out a detailed survey of the property, using our bespoke survey equipment and software. This gives us an accurate CAD drawing which will allow us to start the design process from a position of knowledge. If we are working on a new site, we can recommend a local land surveyor to carry out a detailed survey on your behalf.
This is where we will explore ideas, initially in a sketch format to suit the project. We will look at layout, outlook, sun path, site constraints and neighbouring properties. We will often create two or three proposals to maximise the options and how spaces interact. It might be that we amalgamate ideas from differing options to create a further or final design.
At this stage, we will work up the design proposals to an agreed solution, including looking at the exterior and interior design in more detail than at the concept stage. We look at materials and how they interact and use 3-D software to show the building in a more understandable way. On some occasions, where the application is more contentious, we will contact the local planning office to discuss the project prior to making a formal application.
The next step is to prepare the drawings and make the planning application. We deal with all the administration involved in making a formal planning application on your behalf.
Prior to starting your building work, you need to gain a Building Standards Approval, which is required for all but the most basic work. This includes a detailed pack of drawings, which sets out items like insulation, suitability of materials, structure, and drainage. We will liaise with other consultants such as the Structural Engineer and apply and administer the application to the local authority on your behalf.
We prepare detailed construction drawings, schedules and specifications to convey all the building construction requirements to the builder. This goes well beyond the more basic drawings required for a Building Standards Approval and includes items like floor and wall finishes, lighting specification, staircase design and even down to door handles. The builder won’t be able to price your project accurately if they don’t have this information and providing a full set of production drawings, avoids issues and disputes at later stages.
The success of your project will be linked to the builder you choose to construct it and how your agreement is set up. We advise that you seek competitive tenders from suitable companies and we can manage that process for you, sending out the paperwork and checking tenders for you. We can also recommend builders we have worked with successfully in the past.
We often come across projects that have no formal agreement or contract, making disputes difficult to manage and resolve. As such, we will set out a formal contract between you and the builder, prior to starting the work. This sets out when they get paid and how much, how we deal with changes, what happens if the project over-runs and how defects are dealt with. We will inspect the works on site on your behalf, checking for conformity with the contract drawings and that workmanship is to a suitable standard. We also liaise with the builder to make sure you receive the suitable certificates and paperwork at the end of the project.
How much does our design service cost?
We prefer, where we can, to provide you with a fixed cost for your project.
We have detailed below a generic proposal, based on a bespoke house extension, such as a sun-room, costing in the region of £60,000 excluding VAT.
or 20% of total fee (ex vat)
or 15% of total fee (ex vat)
STAGE 4 A
or 25% of total fee (ex vat)
STAGE 4 B
or 10% of total fee (ex vat)
STAGE 4 C
or 5% of total fee (ex vat)
or 25% of total fee (ex vat)
The complexity of the design and site matters may reduce or indeed increase the fee, so please get in touch to get an accurate quote.
Note – Consultant fees and application costs are excluded and paid direct by the client.
or 13% of the build cost (ex VAT)
How much will my house extension cost?
Estimating the build cost of an extension can be a difficult task, with so many factors that influence the cost, including the size, complexity and site access. We can though, lead you through the process to understand the costs better and help you make informed decisions.
How do we estimate cost?
As a starting point we always do our best to work to your budget, so understanding this at the outset is important. Before we start designing, we will try and analyse what you are trying to achieve and work out if this is viable, before we put pen to paper. There isn’t any point spending time and money if the budget and aspirations aren’t compatible.
Once we have worked up initial concept designs, we will look at working out an approximate cost based on square metre rates. This is a fairly blunt way of working out the cost and only really works for simpler projects. A simple house extension with good access for building, on a flat site, might be as little as £2500 per metre squared plus VAT, but rise to say £2750 on a more difficult site. Some of the more architectural projects we have worked on can rise to £3500 or even £4000 per metre square plus VAT.
How do we obtain more accurate costs?
Until the project goes to competitive tender to a list of building contractors, you will only have an approximate cost to work to. To gain more accurate costs we often employ a Quantity Surveyor, who can prepare a Probable Cost for your project. They will analyse each element and make assumptions based on their experience and costs from previous projects. This is a much more accurate way of preparing an estimate for your project. This method is particularly suited to projects where there are internal alterations in addition to the actual extension. Remember that the square metre rate reduces the bigger the project gets due to economies of scale.
Where can I make savings?
The areas where we often see costs rise are where high-end sliding doors and rooflights are specified. We all like the minimal lines of some of the high-end door manufacturers like Maxlight, but these types of doors can cost two or three times other options. If you want that look, go for it, but it could add another £10 to £15K to a build. Expensive kitchens are another budget buster, with some companies charging large mark ups for fairly run of the mill kitchens. Don’t discount using Ikea or Howdens and finishing it all with nice bespoke worktops. Flooring is another area that can mount up so shop around and make sure you have looked at quality as well as price. We can though use our experience to guide you through options.
How much will my extension add to the value of my house?
It is difficult to put a value on good design and a valuation surveyor may not include good design in the value of the property, but a purchaser is more likely to see the true value. Don’t forget it is difficult to value the enjoyment you will get out of an architect designed extension over say 20 years. We have worked on houses that have been very poorly extended in the past and the extension could be argued as reducing the value of the property. Saving a couple of thousand pounds on design fees may reduce the value of the final product and more importantly the enjoyment of the space.
Frequently asked questions
Extending your home doesn’t have to be complicated and we have detailed below some of the most common questions we are asked.
We have an experienced team of Architects and Architectural Technicians and will be able to answer most of your questions or point you in the right direction.
Detailed Planning Approval
Full planning permission is required before proceeding to Building Warrant Approval. A full application can be made, sometimes referred to as a Reserved Matters Application when following a ‘Planning in Principle’ consent.
Detailed plans, elevations, sections, site plans, location plans and design statement accompany the application, providing enough information to allow the local authority to assess the proposals. All the above is carried out by Andrew Black Design on your behalf as part of Stages 0 to 3 above.
In some restricted situations you can carry out work without making formal planning approval. Smaller extensions and alterations, especially to the rear of properties can be classed as ‘Permitted Development’, if the build fits a set of conditions in relation to size and distances to boundaries. If the project is ‘Permitted Development’ we would normally apply for a ‘Certificate of Lawfulness’ on your behalf so you have suitable paperwork in place if you sell the property in the future.
Building Standards Approval
An application must be made for new buildings in Scotland under the Building (Scotland) Regulations. The application is made to the relevant local authority and covers details of items such as wall, roof and floor construction, structure, drainage, insulation and heating.
We do this for you, preparing the drawings and specification and making the building standards application for you. We do all the negotiations with the Building Standards Officers and organise the Structural Engineers’ SER certificate for the whole project, which covers the foundations, exterior beams and lintols and the timber structure, including the roof trusses.
Value Added Tax
In most situations, VAT is applicable on house extensions unfortunately. VAT is also charged on our professional fees regardless of the rating of the actual build, in line with all professional services related to building.
SER Structural Certificate
This can only be issued by an Engineer who is an Approved Certifier of Design (Building Structures). This certificate is issued with the application to local authorities for Building Standards Approval and ensures that all aspects of design of the structure of a project satisfy the requirements of the Building (Scotland) Regulations. This will include the kit structure and elements like the foundations, exterior lintols and the staircase.
We will liaise with the chosen Structural Engineer on your behalf.
Who do I get to build my extension?
The actual builder of your extension will be the key to the success of your project. The decision to appoint a contractor should be based on thorough research of potential candidates and should include details of similar, previous projects and references, current workload, suitable insurance cover and key sub-contractors.
A NHBC registered builder or membership of suitable organisations such as Federation of Master Builders is helpful, but relevant referrals are usually the most important. We don’t usually recommend carrying out a building project without any professional inspections, unless you are relatively experienced and have a good knowledge of the contractor.
The most important part of any construction relationship is the contract and agreement between you. Always use a contract, which states the cost, payment frequency, retention sums, what is included and not included and dispute resolution procedures. If you choose to use Andrew Black Design for Stage 5, we will organise the contract on your behalf.
What is ‘Timber Frame Construction ‘?
We normally use tried and tested timber frame technology, in various forms. Engineered to high levels of accuracy and quality, the system allows speedy construction.
Now used in over 75% of new homes in Scotland, the skills are readily available to make the most of this efficient building process. Using timber from managed forests, timber kits are by far the most environmentally friendly way to build.
Some key benefits of timber frame:
- Significantly simplifies on site construction
- Allows speedy construction to wind and watertight reducing costs
- High levels of insulation and air tightness easily integrated
- Off-site manufacture leads to greater control and quality
Energy Efficient Homes
- We appreciate that energy use and its resultant cost is a major factor for most self-builders. Further to this, our designs allow integration of many alternative energy saving technologies and offer the option to upgrade insulation levels and specification.
- Timber kits allow the use of the highest efficiency insulation materials and reflective breather membranes, meaning walls can exceed current building regulation. We also make the most of Accredited Construction Details, issued by the Scottish Government. which, when followed correctly, allow the reduction of air leakage in the building, reducing heating and energy bills substantially.
Preparing energy calculations such as SAP and U-values in house, allows us to design our houses around the whole energy use of the building, rather than just individual elements. We can then take into account the heating, lighting, solar gain and heat loss to ascertain the actual energy use and CO2 created.
Our house extension designs will allow the easy integration of various alternative technologies. Whether you are planning a heat pump from water, ground or air sources, our floor constructions can be altered easily to allow underfloor heating to be used, the most efficient use of heat pump technology.