Are you thinking of extending a house in the UK? If so, these are my top 5 house extension design mistakes. I am not talking about the planning system, building regulations or construction methods, I've written other blog posts about those topics. In this post, I am discussing pure design mistakes. These are big strategic decisions that you need to get right, so your house extension is the best possible space for you. Even if you get planning permission and you build a house extension on budget, it can still be a waste of time and money. Stay tuned to find out why.Â
I offer online consultations to homeowners right across the UK and I see many of them about to make these mistakes. I also see them thinking of buying homes that already have badly designed extensions, built by previous owners. Sometimes we have to consider knocking them down, it’s that bad. Again, I’m not talking about the standard of construction. The builder might do an excellent job, but none of that matters if the extension design isn't right. Let's get started.Â
Don’t stick an extension on the side of the house
This is the biggest house extension design mistake I see people making. They need more space, maybe an extra bedroom or a bathroom, and they literally stick the new room onto the side of the house without stopping to consider alternative possibilities.Â
When it comes to conservatories, this is less of an issue, because a room with that much glass should be kept separate from the house, otherwise it will roast in the summer and freeze in the winter. But I’m talking about conventional, habitable rooms that are used all year round. Just to be clear, sticking a new extension onto the side of your home is the cheapest way to build more space because altering inside a house is disruptive and can get expensive, particularly with older properties. The thing is, I’ve found that people stick house extensions onto their homes because they can't imagine how to get more space from the existing layout. I've seen this so many times, and I get it, if you’ve lived in a house for decades, it's possible to become so attached to it that you can't imagine it any other way.
I do a lot of work on older properties and I've seen this play out over hundreds of years. Each generation adds another box on the side of the house. You end up with rooms that originally had windows being covered over by new structures. Those rooms become much darker, and less appealing, so the occupants don’t use them as much. And then they think, we need more space, let's stick another extension on the side.Â
This is why you need to speak to an architect because we can usually see the opportunities and the problems at a glance.Â
Sticking a box on the side of your house might save money but it will cost you in the long run. Even if it means you build a smaller extension, trust me, integrate the new with the old and think about the house and the extension as one cohesive unit. The more space you add to the original house, the less likely that house is going to function as it did. The house won't flow. So, if you are able to fundamentally rethink the entire house it will be much better than just making it bigger by sticking a box on the side. You might need to rethink the location of your kitchen or even the entrance to the house. Ive done this any number of times and if you plan this out properly, the end results can be so much better than the sum of its parts.
Don’t use too many materials
I’m not going to get into whether an extension should match the original house or contrast with it. I've done both, because sometimes it's appropriate to blend in and other times it's right to stand out. No matter what you do, it's really easy to mess up the design of your new extension by having too many materials on the wall. A simple rule of thumb is to have no more than three materials, and one of those three is the glass in your new windows.Â
You want to know why this is and, to be honest, I can't give you an easy answer. It's just more likely to look wrong if you have more than three materials. It's easier to explain this in practical terms. The more materials you have on a wall, the more tradespeople you need to build it. If you have brick, render, timber cladding, zinc and windows in your house extension, each one of those needs a different skilled trade to carry out the work.Â
That will increase the odds of a mistake in the design process, or during construction, leading to a failure. Like water getting into the building because a junction between the different materials wasn't done properly.Â
I could go on about this all day but, let's just say, in my opinion, any more than three materials on the wall and your building will look increasingly unattractive, cost more to build and be at risk of failing in some way.Â
Don’t let the extension dominate the house
Size matters. But more importantly, relationships matter. The bigger the extension, relative to the original house, the more problems you will encounter. In my opinion, once you add more than 50% new floor area to a home. You are no longer really building an extension, you are completely re-designing the house from scratch.Â
We could get into a discussion on proportions. And, believe me, that is a whole other blog post. But, to keep it simple, keep the extension subservient to the original house. It shouldn’t be taller, it shouldn’t be further forward than the front wall of the house and it shouldn’t sprawl.Â
If you really feel you have no alternative, then try to keep the extension one storey tall and make it the central focus of your home. The kitchen, living, and dining space. You can then convert the existing house into a dormitory, with all the bedrooms. Maybe create a new main entrance in the extension and, hey presto, the entire house has been reimagined.Â
But, sometimes, you have to ask yourself, why not just buy a bigger house? I know that’s not what you expect an Architect to say but, sometimes, it's just not possible to get everything you want.
Don’t use complex geometryÂ
I can see some people having a go at me in the comments but, if it ain't a right angle, it's a wrong angle. This is just like having too many materials on your wall. It’s hard to explain, but it looks, off….somehow.Â
And I'm not just talking about fashionable fractals, or contemporary curves, designed by high-profile architects. If the plan of your house extension starts to sprawl, the number of junctions increases, the roof geometry gets increasingly complex and before you know it, your design is out of control.Â
Take it from me, even professionals can get this wrong. Keep the layout and shape of your house extension as simple as possible. Construction is difficult enough without fractals.
Don’t forget to build an Intermediate space
This is only a mistake if you don't include it. Design is hard, even for professionals with training and experience. If you’ve never done this before, it can be overwhelming. I can see why, if people spend so much time struggling to get the internal layout right, they don't think about the landscape. The extension just gets dropped into the garden. Maybe you’ve got a patio door and just walk outside, I’ve done it myself. But there is a better way and you should consider it from the outset. Create an intermediate space, an in-between zone between the inside and the outside.Â
One way to do this is to span the roof out over a seating area, create a nice sheltered deck, sit back relax and enjoy your garden. Take it from me, once my clients experience this they can't imagine living any other way. Even up here in Scotland, these spaces are really useful because they allow people to be outside more often, to get more from their garden than they otherwise would.
Book a Consultation
So if you are thinking about altering a home anywhere in the UK or buying a house that needs to be adapted to suit your needs, check out the RealLifeArchitecture.co.uk website. It's full of free guidance and blog posts packed with useful information for homeowners.Â
You can also book a consultation with me if you need specific advice about your property. Please read the terms and conditions before you book.Â
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