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Double-Storey Extension Costs

Material Costs, Labour Fees and Time Frame Estimates for Double-Storey Extensions

If you plan on installing a two-storey extension, expect costs to be around £60,000— although this can be largely affected by where in the UK you are residing. A two-storey extension that has a basic style and features only two or so windows minus major plumbing or major electrical additions could cost you about £40,000.

Meanwhile, a more high-end extension replete with kitchen space, bathrooms, and other miscellaneous additions could cost around £100,000. For material costs, the final figures would usually be based on numerous factors including the material finish, quality, and size.

The addition of a two-storey extension dramatically increases the overall size of the property. You’ll likely get a number of new rooms to your property, so make sure to factor in the labour and material costs involved especially in terms of furnishing, decorating, and finishing the rooms. Overall, the extension cost can be around £1200 to £1800 for every square metre.

Prices for Two-Storey Extensions

A huge factor that can affect the costs of this type of extension is the preferred finish once the new space has been successfully put in place. Here are some common finish types you can choose from and what each of them includes.
Basic – This finish contains only the bare necessities.
Average – Contains a mixture of bespoke and basic items.
Deluxe – Features top-quality fittings and fixtures.

To serve as a guide on two-floor extensions, below are some estimates:

  • Two-floor small extensions are roughly 30 square metres.
  • Medium-sized two-floor extensions are around 60 square metres.
  •  Large extensions are generally sized at 100 square metres

It is important to get a good grasp of how much the cost for every square metre is based on size for large-scale extensions. Generally, deluxe extensions that are larger will usually be cheaper per square metre. However, compared to budget finishing, the overall costs will still be immensely greater.

Cost Breakdown

A two-storey extension of 60 m² in size will generally cost an average of £70,000. Of that, 75% will usually be spent on the materials, 60% will pay for the labour costs, and the remaining 5% should cover the costs for waste removal.

Time Frames and Labour Costs

It is common for most builders to charge £1,200 to £1,800 for every square metre of a two-floor extension project. This roughly translates to a daily rate of £150 £250 for every labourer. Rates will vary based on their skill set. Note that home extensions will need more than a single builder.

Among the tradespeople you probably need are a plumber, an electrician, as well as landscapers. How long it would take for the project to complete will also be based on the overall size of the project.

Remember that just like any project, a job done right needs proper time. You’ll also have to account for possible delays and setbacks and this can add to the final costs too. This is especially true in extensions where you have to juggle multiple jobs carried out by different tradespeople.

Naturally, smaller extensions will require less time. It’s also important to remember that proper permits and authorisations are required before any work can commence. Planning applications usually have a processing time of 48 hours. Full-plan submissions will take longer due to the detailed drawings involved and can usually take up to 8 weeks.

Cost Factors to Consider

Several factors can also influence the time-scale and costs involved in two-storey extensions. Take note of all your options and always have a plan in case something unexpected comes up. To make sure that you’re always prepared for contingencies, set aside a supplemental budget of at least 10% to 20% of your project’s expected cost.

Below are some of the possible trades that you might need to tap for the project along with the specific costs for the work that they will perform if they are to work on an average finish, medium-sized build.

Fees for the Structural Engineer and Architect-£12,950 Design and planning are integral steps to an extension project. Initial costs for getting the plans done can be around £1000. If you get an architect to serve as a project manager, the fees would generally cost from 3% to 15% of your overall cost. For a build that costs £70000, their fees will likely get raised around £2100- £10500. Other extra costs you might need to cover include:

  • Assessment for flood risk costs £600
  • Costs for building control £700
  • Tree report costs £200
  • Planning permission is £200
  • Party Wall Contract is about £750 or more

You may need to consult your preferred structural engineer to assess whether the building is in good ,shape and still structurally sound. This could cost you around £500 to £1000.

Drain Work, Foundations, Roofing and Brickwork- £23,500 Extensions that are medium-sized will likely require around £6000 for the foundations. Getting a drain permission may cost about £200 to £1,300 for the application fees.

The actual work would usually amount to £8000 although this would be based on the overall size of the extension. The average cost for
roof installation would be around £4500.

Doors, Windows, Landscaping, Patios and Rendering- £10,000

Once the extension has been completed, your garden might also need to be renovated. Your property’s exteriors might also benefit from decorating. It’s typical for professional landscapers to charge £100 per square metre although the cost will usually already include the materials that they will use.

If you have an extension added towards the rear, you’ll likely need to lay a brand new patio— especially in the case of extensions that are fitted with a door that directly connects to your garden. Price for patios varies although the typical costs could run up to £1800 with labour and materials included.

You’ll need to install windows and doors once the extension has been completed too. For a single external door and say, 4 windows, costs could be around £3500. This will be higher if you go for custom- made ones.

Costs for external rendering can vary based on the extension size or if you just want to have it covered. It would be prudent to set aside about £3700 with painting and pebble dash included in the costs.

Appliances, Fittings, and Fixtures for Bathrooms and Kitchens- £17,000

Getting a kitchen remodelled and having a brand new bathroom fitted will not be cheap. But it is always best to invest in top quality items that will really compliment the new space.

When done right, they could potentially lead to a more economical home as a result. Refitting a kitchen can cost around £10,000 which already includes decoration, professional installation, counter tops and white goods.

If you’re looking for a really good bathroom suite in terms of quality and one with equally impressive decoration, flooring and tiling, expect the costs to be around £7000.

Just note that the figures can fluctuate depending on the design you choose as well as the overall quality of the materials you select. Depending on the goods you will decide to install, you may also need a gas engineer, electrician and a plumber.

Interior Finishing and Fixtures Such as Decorating and Plastering- £6,550

Generally, plasterers will charge on a per hour basis. For larger jobs, however where multiple rooms are involved, they may choose to give a quote based on the job that they will do, not on the length of time that it would take them to do it. If you have an extension with 3 additional rooms, the whole project may cost you around £700.

Decorators and panthers usually charge £150 to £200 as a daily rate. A work that requires the application of two coats of paint for every wall can be done within two days, with drying time accounted for. In the event of large scale projects, decorators can be expected to work with a partner to reduce the time they need to spend on site.

Electricians typically charge £230 daily. Most would prefer working in two due to safety and health considerations. A bigger extension might require more people. Costs covering the electrical work involved will usually be affected by the overall quality of the fittings and fixtures being used— so, take

note of this when setting a budget. See too if the current boiler in your home will have the capacity to support the extension. In the event that you may have to replace it, expect the costs to be around £2500.

Planning the Extension

Several points should be taken into consideration when planning the extension to ensure that you will have proper contingencies put in place in the event that something unexpected may come up.

  • Determine if your home can benefit value-wise from the addition of the extension. So, make
    sure to take note of the current price ceiling for properties where you are and the current
    market value as well as the impact that your extension is expected on your expenses.
  • Set achievable goals with your budget in mind. Set aside an emergency fund of about 20% of the total projected cost.
  • Consider how you’d want to use the space for the extension. Have a layout of the extension’s floor space and how it can be accessed and the changes it may cause to the rest of your current floor space.
  • Check if there’s a possibility of the extension overlapping with or comes too close to any existing drain. In this case, local permission will be needed so you can relocate the drainage system of the property before work can commence.
  • See if your existing electrical circuit and boiler have enough capacity to bear the added load or if there is a need to replace them.
  • Surveys may need to be undertaken to determine whether it’s safe of the extension to be undertaken. This includes soil type tests and assessments for flood risks.
  • Consider property access and the overall accessibility of the location. Areas that aren’t as easily accessible may face delays, especially in the transport of materials to the site or from it.

Ready to get a quote from local tradespeople?

What’s Involved in Double Extension Construction?

Step 1- Planning

You’ll need plans that detail the new layout. An expert structural engineer or an architect can help planning the design with your aesthetic preferences and budget taken into account.

Find out if planning permissions are needed and see if there are party walls involved too so the necessary documents can be processed and applied for ahead of time.

Step 2- Groundwork

This is where the foundations get measured based on what the floor plans have indicated. There will also be a need for building control to check the location to ensure that work is highly satisfactory. They will also advise reinforcements of necessity, especially with the foundations that are being laid.

The drainage and pipework may also require modification at this point before pouring the concrete in. Landscape work may also be needed, especially if the new building extends toward your garden space. A new patio or path may also be needed. For extensions that extend to the garage area or parking space, it may be best to consider other parking arrangements or the possibility of getting a brand new driveway laid down.

Step 3 – Main Build

After successfully setting the foundations, the exterior walls will be built. Scaffolding is likely required for a two-storey construct, so make sure that this is accounted for in your budget. After the frame has been set in place, interior walls will follow, along with the construction of the roof. The covering will also be fitted in. The doors and windows will get fitted in next along with the exterior pipework, guttering and
pipework for your exteriors.

Step 4- Fittings

After weather-proofing the structure, plumbing, electrics and first fix carpentry will follow. This is the stage where kitchen or bathroom extensions will take form. Any required plumbing gets routed to your preferred location as has been detailed in the layout plans. Electrical wiring will also be installed along with the plug sockets and lighting. Plastering will also be carried out. After drying off, wallpapering,
painting, and tiling will follow along with the floor laying.

Step 5- Finish

After decoration has been completed, you can install fixtures next. If you’re fitting in kitchen extensions where you need radiators, they will be installed at this stage. Bundling control will also sign off paperwork once proper assessments have been done.

Kitchen Extension Costs

The kitchen is perhaps the most popular room that gets extended. Often, this is due to an owner’s desire to have a multi functioning kitchen and diner space rolled into on or simply because the old kitchen just didn’t provide enough space. A kitchen can cost you up to £10,000 depending on where you are in the country.

This is on top of a building extension which costs could run around £30,000 to £50,000. Kitchens are a great addition to any home, especially where market value goes, provided that the fixture blends well with your existing property. A high-end, ultra-modern kitchen would look off when added to a rather traditional-looking property.

Accessories that are overly-fancy or those that seem to look rather out of place might put off future buyers. This is why whatever extensions you decide to pursue, always take note of the future market potential of your property before moving on to the next step.

Bathroom Extension Costs

Most home buyers want a property to have at least 2 bathrooms with more being highly preferred. Purchasing a bathroom can cost as low as £700, with the charges for fitting it in already included. However, the numbers could increase if you’re overhauling your existing bathroom to give way to a brand new suite, flooring, and tiling, increasing the costs to £3500. Wet rooms, these days, are quite popular thanks to being practical and looking sleek. They are also very practical especially for households where a family member may have mobility issues. It may be something worth investing on especially if you have the budget to spare. Generally, the installation of wet rooms usually starts at £5,000.

Other Trade Costs

Home extensions will likely require the services of a wide range of people to get the work completed. You may require the services of the following people when constructing a property extension:

Builder – Based on how big or small an extension is or how complex it is, the average costs for a builder will be around £150 to £250 daily. To ensure that you’re referring to the most capable people for the job at hand, it is advised that you take note of a number of choices, ask for quotes and then choose those that can offer the most value for what you’re spending.

Roofer – You’ll need a roof construction specialist when getting an extension constructed. Roofers in the area usually charge £150 to £225 per day.

Plumber – A plumber may be needed especially if you have a bathroom or kitchen extension. Typically, plumbers will charge a daily rate of £150 to £200.

Electrician – An electrician will be responsible for the installation of new wiring on the new extension. He will also be responsible for ensuring that the current system has the capacity to handle any added output brought about by the new extension. Most electricians will charge a daily rate of £120 to £350 with those located around London charging more than the rest of the country.

Kitchen Fitter – If the extension includes a kitchen extension, kitchen fitters will be needed and they usually charge £120 to £160 daily. If you’re into bespoke designs, you may want to ding up for the services of kitchen specialists.

Carpenter/Joiner – If there is woodwork involved with the extension, a carpenter or a joiner will be needed to complete the job. They will be responsible for the installation of wooden floors, wooden cladding, and even bespoke furniture. Expect them to charge you around £130 to £180 per day.

Plasterer- Tasked for plasterboard installation on your ceilings and walls, plasterers generally charge £100 to £200 a day. Plasterers may also be able to render external walls.

Decorator and Painter – Depending on how extensive the decoration project that you require is, decorators and painters may just choose to work alone or work in pairs for more exhaustive projects. Expect them to charge a daily rate of £150 to £200.

Floor Fitter – You can always go the less expensive route by choosing to get the floors installed yourself. However, professionals are generally more time-efficient so signing up for their services could be worth it. Floor fitters will generally charge £150 to £200 daily and can handle various flooring mediums from carpets to tiling.

How Big Should My Extension Be?

If a wraparound or rear extension is what you have in mind, know that the job will be subject to certain regulations. Failure to comply can lead to thousands of dollars lost just so the issue could be rectified.

Below are important points to remember if you aim to construct a “permitted development” extension where planning permission is no longer necessary:

  • Two-floor extensions should never go over 3 metres beyond your rear wall
  • It must go beyond half of the actual width of your property
  • Must never be beyond 7 metres closer to the boundary of the rear property
  • The height of your eaves mustn’t go beyond 3 metres of the height of the existing eaves
  • Roof pitches should match that of the existing property
  • Materials should also match the ones used for the existing house

Remember that extensions aren’t allowed to extend your property closer to any surrounding roads and lanes. Planning permissions are necessary when an extension is expected to work beyond what these terms have specified. When in doubt, you can always refer to the local authority for advice.

Where to Extend

If you choose not to apply for any planning permission, you’ll find that your choices may be limited. Generally, extensions are constructed to help increase the overall space in any property.

This includes kitchens and living rooms along with bedroom spaces. Some also extend their spaces to add amenities including conservatories, bathrooms and garage spaces. Due to certain building restrictions and regulations with the permitted development, it’s common for homeowners to have extensions built either on the side or the rear of the property.

This process is generally cheaper and quicker instead of having to secure a planning permission when choosing to extend the front of your property. There are also instances when extending to the basement area may be ideal.

Planning Your Roof

In planning the extension, it is important to remember that there are limitations imposed even to the roof. For instance, the lowest part of your new eaves mustn’t exceed 3 metres in height when located within a two-metre distance between within the boundary of your property.

It’s also required for the roof to match the materials used in the existing one, with the only exception being flat roofs. Hiring a reputable roofer or architect will ensure that these limitations are taken into consideration when pursuing the project.

Is a Two-Storey Extension a Good Idea?

With a growing family, over time, your home may no longer feel spacious enough. Rooms might feel smaller and before you know it, you might start considering the prospect of possibly moving to a bigger property or having an extension constructed.

Choosing to install an extension is usually a straightforward decision but for people who live in flats or somewhere that there is no garden, this cannot be a possibility.

Whether it is a good idea to pursue the construction of an extension or not will usually be based on where you are and the resulting financial implications about considering a move. If you’re in an area where property is highly valued, extending will be the most sensible decision to do.

However, proper planning is crucial to ensure that the resulting extension will be professionally constructed. Do remember that a garden area and a parking spot is something that people will expect of any house so make sure that you take this into account.

Single vs Two-Storey Extensions

Assuming that the extension is within the bounds of permitted development, you’ll need to consider multiple factors before carrying out the construction. If your concern is to keep expenses minimal but you still want an extension nonetheless, a one-storey project may be best for you.

Meanwhile, double-storey extensions are usually subject to certain permitted guidelines. However, it does potentially double your floor space once completed. Considering how the costs involved for the roofing and foundation will still stay the same, it might make more sense to pursue a two-storey extension instead.

Is an Architect Necessary?

There is no legal requirement to hire the services of an architect when building an extension but having one in your team is beneficial. They are skilled and have been in the industry for years. They are also well-versed in various building regulations as well as in designing projects that will qualify so, you can prevent a variety of problems when there is a professional architect assisting you every step of the way.

Architects usually charge varying rates depending on the specific duties that they are tasked to perform. For plans, their rate can begin at £1000. If you choose to have him oversee the entire project until completion, they will usually charge their fees based on the project’s overall cost. In most cases, this would be around 3% to 15%, depending on how complex the project is. For instance, if the build totals £70,000, an architect’s fee could run around £2100 to £10,500.

Common Issue with Two-Storey Extensions

Extensions problems often happen when property owners fail to secure proper professional advice in the hopes that they can save as much money, going DIY without having a clue how the build should be carried out, or going for cheap builders. When architects and the necessary professionals are tapped regarding the planning of the extension and you only choose to hire reputable builders, the possibility of things going awry will be generally low.

You’ll want to let your insurance provider about the planned extension to ensure that this is not, in any way, going to end up invalidating your home insurance.

Not having a clear idea of how the extension design should be can also lead to problems later on. Not having a clear vision of what you want and not having a good grasp of the appropriate time frame it would take for the project to get completed can often lead to unnecessary delays later on.

This is why, if you’re managing the project, it helps that you contact the authorities and other relevant companies so you are assured that you are building the extension in a correct and timely fashion. Make sure that the necessary paperwork has also been granted prior to commencing the build.

Time Constraints

Several factors can impact how long it would take for the construction of your extension to get

  • Access to your project site as hard to access location can often cause construction delays. If manual labour is needed to move items that could have been delivered via machinery, then expect additional costs.
  • Delivery of materials must be effectively managed in relation to the specific time-scales when they will be required for the project.
  • Secure approval from the relevant authorities where necessary.
  • Changes to the construction plan can lead delays especially where materials needed and space usage has to be reconfigured.
  • Existing property adaptations can cause delays too such as in instances where drains have to be relocated or when permissions from the local infrastructure authorities have to be secured.
  • Not finding alternative accommodation for you and the family could lead to you becoming the cause of the delay.
  • Extension foundations can be affected by the type of soil on your plot
  • Severe weather can also have an impact on build time.

Can an Extension Increase my Property Value?

Whilst extensions can certainly increase overall property value, it is important to consider the return of  investment for these projects before moving on. Extensions that are poorly-planned and constructed quite disappointingly will only lead potential buyers getting deterred at the prospect of owning the property.

A spacious kitchen is always a good thing especially if it serves a great benefit to the rest of the property. However, if it ends up overshadowing your living space, then it may become a detriment to the future saleability of the house. The same is true with how the extension has been finished as well.

If the finish doesn’t seem to match the rest of the property, it can put potential buyers off. There’s also the fact that while an extension can clearly add value to your home, this may not lead to a higher property selling price.

There are even instances when you’ll find that recouping the costs involved with the installation of the extension will be next to impossible. This is also why you have to carefully ponder the decision especially if you have future plans of reselling your home.

Extension Planning Permissions

Planning permission may be necessary if an extension goes beyond what’s still qualified as a permitted development project. If your property is a graded or listed building or is part of a conservation setting, a planning permission will be required. In most cases, you would at least need to secure consent for listed buildings, regardless whether the extension is a small or big one.

Planning permission costs will be highly dependent on the type of work that needs to be done as well as where exactly you are in the country. Usually, the charge could cost around £200 and will usually take 8 weeks for a decision to be handed down. For complex plans, this may extend to 13 weeks total.

There have been instances when the planning permission got rejected as it was determined to have a potential impact not only on neighbouring properties but also of the local environment. If the plan seems to put too much demand on local waterways and other infrastructure, it might get disapproved. If it’s in keeping with the character of the original building, your extension may also be thumbed down.

Without a planning permission, you may be served an enforcement notice where you’ll be directed to undo whatever changes you have already made to your property. Ignoring an enforcement notice is against the law although it may be appealed for those instances when you feel that it was served unjustly.

Building Regulations for Two-storey Extensions

Building permissions delve into the structural and technical building details to ensure that they are indeed suitable for the purposes they are intended for. This also assesses if the building can be safely used. Below are items that will require inspection and approval:

Party Wall Agreement

The party wall is the boundary separating two properties. For two-storey extensions, there may be a need for you to seek your neighbour’s permission in carrying out the work connecting their wall to your extension. You are required to give them proper notice within two months up to a year from the time that the construction will commence. A plan of work is required as well whilst you’re talking to the neighbours and a written consent is also needed so the work can be started. Your neighbour is expected to respond no more than 14 days from the time of the issue of the notice.

They can refuse, consent or even offer a counter-notice where they may suggest for additional work to be done with them paying the expenses involved, especially if it is something that can benefit them. If a dispute arises, a party wall surveyor will be tasked to settle it and a party wall award will be issued afterwards.

Controlling the Costs

Costs can build up fast, however, there are some steps you can take to minimise them. Here are some tips on how to keep the costs down.

Agree on the prices as well as payment schedule before commencing the work- This helps you budget your funds while also ensuring that the work has already been completed up to a certain extent before you will start paying the tradespeople out.

Keep things simple– Simple, straightforward designs are always cheaper where construction costs are involved. They will take lesser time to complete as well.

Stick to your plans- Changing your mind when a considerable amount of work has already been done can have a massive impact not only on the project’s time-frame but also to the budget. So, stick to your plans.

Manage the project- You’ll save a lot of money if you decide to take on this role. All you need are some excellent management skills and loads of patience and you should be alright.

Demolition costs- If you can, going DIY is going to help you save money immensely instead of having to account for the costs for labour if you get other people to do the demolition job on your behalf. Preparation- If you can complete the on-site preparation yourself, do so and save loads of money in the process.

Shop around- Taking your time to shop around for the materials is essential. This is important so you can find those stores that would be willing to give you some very competitive pricing.

Waste removal and cleaning- Instead of hiring tradespeople for the clean-up once the work has been carried out, doing it yourself will save you loads of money. You can just hire a skip and move your waste
by yourself instead.

Quotes and Estimates: Understanding the Difference

Quotes and estimates are different especially in terms of how they’re calculated and what they entail. Estimates are guide prices for the type of work that is about to be carried out, without the full details known. Quotes involve exact pricing of the work along with the costs of labour, materials, and even VAT costs where applicable.

It is always best to secure a quote in written form from suppliers as this is legally binding offer where they will no longer take back whatever offer they have already extended to you such as increase the price with the exception being when there are additional costs that have to be done.

Finding the Best Builder

The best builder will give you reassurance knowing especially since this is a complex project that you need their services for. Ask for multiple quotes from several builders so you know you are getting nothing but the best service out of what you are spending.

Look at their portfolio to get an idea of the kind of work that they do and the quality of the job that they have carried out so far. Talk to past clients they have worked with as well to find out if they generally have satisfied customers on their wake.

Three-Floor Extensions

A two-storey extension can be a great opportunity for converting into a 3-storey conversion. You can build into your attic and then create a loft conversion for additional living space inside the house.

On their own, loft conversions can cost you up to £30,000. This can be easily incorporated into the design, to help bring the costs down since there is already a construction that is going on with all the tradespeople and labourers present to get the conversion done.

If you’re not confident is this is a good idea to pursue or not, you can always talk to your builder and ask for estimates for some very helpful advice.