The 40 sq.m. Extension

Building an extension is a very exciting project that a family can undertake. It’s a very appealing prospect because an extension affords you the add all those things you feel is lacking in your home in its present plan. Finally, all those ideas, desires, wants and needs can be incorporated if you go about things the right way and with all the help you can get.

Where Do You Start?

Where do I start? That always sounds like a simple question that should have a straightforward answer. Only it’s not that simple. When taking on a pretty big project (yes, a home extension is a big deal) that is going to require huge commitments both financially and emotionally, it’s only natural that you do everything possible to make sure it turns out a success.

So, to answer your question: where to start? Let’s first draw our attention to an erroneous starting point some homeowners curiously settle for when planning a home extension around their premises.

Where NOT to Start – The 40sq.m. Extension

A lot of people believe that they should extend to 40 sqm. to the rear because this does not require planning permission, and is an exempted development. This is an obvious reason to believe this to be a good idea but as architects, it is not the sort of design decision to base the size of an extension and is only one part of the design rationale that an architect will use when designing your extension.

In other words, putting the above mildly, the most important things to consider may go beyond how many acres of space or storeys you are going to build, or where you want to add the extension. For an architect, there are lots of other things to consider than focusing only on how to beat the need for planning permission. Because even if you can do away with the need for planning permission by keeping the extension within 40sq.m., there are a plethora of other tricky waters you must navigate through planning rules, building regulations, handling neighbours, party walls agreement, etc.


Having said that, it’s time we start things at the beginning:

Things to Consider Before You Start

Be sure about planning an extension

When we come across properties where an extension is being considered, it’s sometimes a surprise for us to find that there is so much under-utilised space.

Even though we are trained to see the space the average homeowner won’t see, sometimes, under-utilised spaces don’t appear more obvious than we see them. On that note, are you sure you need an extension? Inviting an architect at the budding stage of the project can help you know what exactly is lacking so you can proceed with more clarity

Will An Extension Add Value?

Home extension projects can be very demanding, whether financially, emotionally or mentally. Hence, it’s paramount that you double-check your plans before you dive all in. It’s always advisable that you solicit the expertise of an architect when drawing up your home improvement works, from conception to completion.

Also, it’s beneficial that you speak to a local real estate agent who is well placed to give a view on whether your plan would add value to your home. Also, they should be able to indicate the amount of this added value, so you can consider that when drawing up the budget for the project. Ascertaining whether value-added is greater than the cost of the project may be a difficult thing to assess, but finding similar properties within your vicinity and see how much they are sold for can be a good place to begin.

An extension project, when done right, is an investment that solves not just your immediate needs but those of the future occupants of the house, should you decide to rent or sell in the long run.

How To Design An Extension

When it comes to designing your extension, a lot depends on your capabilities and whether you want to carry it out alone or work in tandem with an architect. Another route to take would be to work with an architectural company that’s capable of designing and building the extension from start to finish, however expect that this route will ultimately compromise on design.

An extension project can be very exciting to undertake. Hence, homeowners can who are looking at one can be rarely accused of lacking passion and enthusiasm for such home improvement works. However, unless you’re equally very experienced and knowledgeable in renovating properties, you’re better off going down the professional route.

Yes, that will mean more cost for the project because you have to pay the hire’s considerable fees. But remember, this is an investment. Even the cost of hiring expert talents should be seen as an investment because they contribute to the overall quality of the product or the extension. Furthermore if you do not invest in good design, your overall investment may turn out to be a dud if it is not well designed.

The 40sq.m. Extension And Exempt Developments

In Ireland, the exempted limits for house extension is 40sq.m. when built to the rear of a house on the ground floor, leaving a minimum garden area of 25.sq.m. The type of domestic works covered includes construction of an extension or conservatory, conversion of a garage, store, shed, garden or other structures for domestic use. These structures or extensions can be added to the rear of the house.

For any house renovations to fall within exempt development, it must not increase the original floor area by more than 40 square metres – whether as a single or two-storey extension – where the house has not been extended before.

Otherwise, if this is not a first time extension, the combined floor area of the proposed extension together with any previous extension must not exceed 40 square metres – including those for which you got planning permission.

For terraced and semi-detached houses, the area of any first-floor extension above ground level must not exceed 12 square metres. Again, this amount should be the total including any previous extension already in place.

For detached two-storey houses, the first-floor area can only be extending to 20 square metres. Anything beyond that limit will require planning permission.

Attic conversions, for most cases, are exempted from planning permission except intend to install dormer windows or Velux style roof lights to the front of the house. However, before you begin any construction, always double-check that you are within permitted development rights. This is because some of these regulations in questions differ from locality to locality. Hence, there is likely a notable difference in how local planning authorities interpret and enforce planning and building regulation laws.

What About Height Restrictions?

In fact, yes. There are certain restrictions to the height of the side and rear walls. Exclusive of gable walls, any walls erected in the course of adding an extension must not exceed the height of the existing walls or structure.

Permitted Windows Placement When Extending

When adding an extension, you’re restricted as to how you can place the windows in the new structure. Also, first-floor windows cannot be placed less than 7 metres from the boundary they face.

Budgeting For Your Home Extension or Renovation Project

Budgeting for a home extension or renovation project requires considering so many things, most of which is dependent on you and the present state of the property in question.

Nevertheless, we must work with a budget. So, a good rule of thumb is to set aside €2000 to €2500 for every square metre of new build works including extensions. While for renovation or refurbishment projects, between €1000 and €2000 per square metre depending on the current condition of the house in question.

It must be clearly stated that the above figures are estimated for extension/construction works, electrical works, plumbing services, fittings and finishes only. Those figures do not include the cost of procuring things like windows, bathrooms finishes and kitchens. All that will have to come under a separate budget.

Before you begin any construction, it’s highly recommended that you seek the advice of an architect. Bounce off your ideas with an architect and let them advise you on where best to invest your money in your home that will give the biggest return on investment (ROI). Also, they can always recommend cost-effective ways to go about executing the project. Most architects will also be able to help you with the likely cost of construction materials and reliable suppliers you could use. Ultimately, a well-grounded architect will ensure you have your dream home while staying within budget, simple as that.


How Big Should The Extension Be?

When it comes to extensions, bigger doesn’t necessarily mean better and vice versa. The size of an extension is typically a reflection of so many things: how much you have to spend, the purpose of the extension, what you want and need from the extension, you and your family lifestyle choices, etc.


When deciding on an extension, you mustn’t compromise the purpose of the existing structure or house. The bigger the extension, the more likely it renders some spaces redundant. You must spend some time re-evaluating the layout of your home, identify any unused spaces, and see how you can incorporate the new structures to maximize untapped potential.

Don’t Fall Under The 40sq.m. Extension Spell

We often see many homeowners settle for under 40 square metres expansions simply because they are afraid of the perceived hassle associated with planning applications. This should not be the case. Don’t be afraid of going through the largely straightforward process of obtaining planning permission. Don’t let the fear of it restrict or dictate the size of your extension. Like we come across every day, there’s absolutely no reason to settle for a modest 40 square metres extension when a larger extension could give you more benefits, scope and flexibility.

Furthermore do not think that you have to build a 40sq.m. extension to use up all of your exempted rights, most of the time we architects know that you need a lot less when the design is well thought out which will ultimately save you on cost.

Getting An Architect Involve In The Extension Project

There are uncountable reasons why getting an architect onboard is the wiser thing to do compared to going solo. Yet, some people still wonder at what stage of the project is right to bring in an architect.

We recommend them at the beginning. You should have them right when you are drawing up the budget. Hiring an architect is much more than just having someone draw fancy designs for you, No. An experienced and seasoned architect in house renovations and extension will save you money, time and energy while guiding you through every step of the way.

They have most likely done very similar projects like yours in the past so can alert you where the pressure points are so you can plan for them. They can help you draw up a more realistic budget, help you with the initial ideation sessions, recommend other expert talents like plumbers and electricians you’d need, and introduce you to trusted traders and building materials suppliers. All these make it a no-brainer to involve them as soon as possible so you can benefit from their guidance from the very start.

The Construction Process And What To Expect

The construction of a home extension is a very demanding and tasking endeavour. Unless you have been around and centre where many of such building projects are been executed, it can be overwhelming. Architects, thankfully, understand the nitty-gritty of home renovations and extensions. Having them in your corner means you get to understand the what, when and why every operation has to occur in the way that they do.


Also, the architect will be on hand to answer any questions that the builder may have. Brace yourself, as soon as the builders begin work, things move quickly. Questions do arise, some as expected while others peculiar to your project. You will have to answer these questions quickly and make decisions under tight time constraints. Your answers have to be spot on and timely. Otherwise, you risk avoidable delays and extra expense that may result from a bad answer or decision taken.

Working With Building Contractors, Builders and Suppliers

Handling contractors, builders, and materials supplier is no easy task when you go it alone. Your lack of a relationship with these people certainly counts against you in terms of the cost and the quality of work you would receive. But when you employ the services of an experienced architect, it’s more likely that the people who will eventually carry out the work are those the architect have a working professional relationship with. This helps because the architect brings them to work so is more likely to get a tune out of them than you could ever manage as a first client.

Furthermore, the architect over-seeing the build for you would be able to tell what will add value to your home and what would not. In addition, when it comes to managing the project within your budget, an architect is invaluable in this regard. Say, you have exceeded your budget and looking for avenues to scale back, your architect will be able to tell where you can cut costs – such as finishes – without compromising the structural integrity or overall quality of the extension.

A Word Of Advice About Home Renovation

When carrying out an extension or home renovation, it is paramount that you begin with a plan and adhere to it throughout the process. Waking up one morning and improving a section or part of your home is only going to highlight other areas where your home needs retouching. So, a proper and holistic approach to home extension is essential. When you take a scattergun approach to home improvements, you’ll most certainly spend more than you needed to without much value added to your home.

Seek advice if need be. But never dance to the tone of a contractor, builder or supplier. Demand they present you with several alternatives so you can make your decisions instead. A good architect will be able to present you with different options while the final decision should always rest with you. Anything short of that, you probably don’t want to work with them.

Happy Extending!!!

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