gARAgE convERsions
Hands up, who actually keeps a car in their garage? Don’t let your garage become wasted space — use it to extend the useable living space of your home and reap the rewards. Natasha Brinsmead explains
garages these days are rarely used for storing cars, and are more likely to be spaces for depositing items that no one quite knows what to do with — a convenient dumping ground in which to hide away rarely used equipment.
However, the space potential of garages cannot be ignored. Converting garage space into extra living space is one of the most costeffective and least disruptive ways to ‘extend’ your home.
In most cases, converting a garage will fall under Permitted Development — particularly if you don’t plan on altering the structure. (A Lawful Development Certificate is a good idea, though.) However, if you are converting a separate, stand-alone garage, as opposed to an integral one, then you might find you have to apply for a ‘change of use’.
If you live in a listed building you will almost certainly require permission. Those in conservation areas may also have to apply for permission to convert. It is also worth checking out – particularly if you live in a relatively new build – that there is no condition attached to the garage stating it has to remain as parking. In this case, an application would need to be submitted in order to remove this condition.
This will all depend on the scale of the project and what you are hoping to achieve. Some people choose to come up with a design themselves and then carry out all the work they can on a DIY basis. Obviously this is a great option for those on a tight budget and with plenty of time on their hands.
However, using an architect, architectural designer or similar will usually result in a design with a little more flair, plus they will have experience of dealing with building control. Design fees for this type of project can start from as little as £1,200£1,500, rising to at least £3,000 depending on the complexity of the design.
A quick search on the internet will bring up plenty of garage conversion specialists, too. These companies usually have a wealth of experience in dealing with planning issues that can arise with this type of project as well as the Building Regulations surrounding them. It is, however, always worth checking out their previous work and speaking to past clients.
A good builder (aim for someone who is recommended and who is part of an accredited body such as the Federation of Master Builders) will also be able to take on a garage conversion.
Integral garages will almost always have a lower floor level in the house. This would have been a requirement when they were built to avoid any liquids that might spill in the space from entering the house. Of course, if you want to integrate the garage into your living space, it will be preferable to raise the floor level — this is most commonly done through the introduction of a damp-proof membrane (DPM), insulation and a new screed, along with a final floor covering.
It is unlikely that the garage will have been built to include floor insulation, but if this is to be a habitable space then this will need to be rectified — it is also probable that a DPM will need to be introduced, or at least upgraded.
You can use the existing concrete floor as a base, adding a DPM (solid or liquid). A layer of insulation can then be placed on top of this — you will need to liaise with building control to ascertain how much insulation will be required.
Finally, screed can be poured, ready to take your new floor covering. Care needs to be taken that the new floor does not cover any existing air bricks in the new house, extending them through the new floor if necessary.
Before dealing with the floor levels, consider whether you might want to include underfloor heating within your conversion.
Where there is a very large difference in the floor levels, constructing a new suspended timber floor, with a void of at least 150mm between the concrete and underside of the timber, within the old garage space might be the best option. Insulation can be placed between the joists, with air vents introduced to provide ventilation.
is The roof sound?
If, on inspection, you see that water is lying in pools on the flat roof, then this has the potential to cause problems in the new space beneath. The roof will need repairing and the underlying fabric of the structure checking for damage.
Occasionally it is necessary to replace the entire roof. This is sometimes a welcome discovery — swapping a flat roof for a pitched design can help tie the new space in with the rest of the house, aesthetically, although you may require planning permission to do so.
“Basically each element of the garage conversion (walls, floor and roof) will have to be constructed and insulated so that its U value (rate of heat loss through that element) meets or is less than the value stated by Building Regulations,” explain the experts at insulation specialists Kingspan.
“In England, you need to reach a U value of 0.28W/m2K for the extension of existing buildings. In Wales, it’s 0.21W/m2K. In Scotland, you need to reach 0.019W/m2K where the existing building has U values worse than 0.70W/m2K in the walls and worse than 0.25 W/m2K in the ceiling. If the U values are better than those figures then you need to reach 0.22 W/m2K.
Garages are usually built with a brick or block single-skin solid wall, without any sort of insulation, according to the Kingspan experts. “Assuming that you are not going to tear down the walls and start from scratch, there are two methods of adding insulation to the garage wall — either to the inside or the outside of the wall.”
In the majority of cases, adding external wall insulation to an attached garage is not recommended, as although it minimises the impact the extra insulation will have on the internal spaces, it can cause issues externally with wall thicknesses. For this reason, internal insulation is usually the preferred option.
The simplest method is to use insulated plasterboard, fixed to timber battens that are protected by a strip of dampproof course (DPC) placed between batten and wall. Alternatively, insulation can be placed between battens, before a fireproof plasterboard is fixed to them.
In the case of roof insulation, if there is already a room above the garage then this is not an area that will concern you, but in the case of old flat roofs, you will need to once again look at either upgrading or installing new insulation.
Insulation can either be added above and between the roof joists (warm roof) or below and between (known as a cold roof).
When converting a garage with a flat roof, you will need to achieve the following U values:
l England 0.18 W/m2K
l Wales 0.15 W/m2K
l Scotland 0.15 W/m2K
Where you are filling in the space left by a garage door, adding new doors or windows, or building up and above the garage, the existing foundations will first need assessing. You can either contact a structural engineer to investigate for you or dig a trial hole and ask building control to come and view the foundations.
Some garages were built with a continuous foundation across the front, in which case, it may be fine to build on.
If the foundations are found to be inadequate (or absent), there are several options that may be offered. You’ll likely need to build new foundations to support the infill wall, the depth of which will depend on the soil conditions and any windows and doors you plan on including.
Ideally you want to make your garage conversion look like part of the rest of your house, as opposed to a converted garage. This should be something you can work on with your chosen designer.
One exception is in the case of partial garage conversions. This is where the front of the garage remains unchanged both internally and externally, while the rear section of the garage is incorporated into the house. This allows you to retain some storage space, while gaining a little extra living space — perfect for those after a utility room, a little extra kitchen space or a playroom.
Making sure that the materials used for the cladding and roof (where there is one) match or tie in with those on the main house ensures a seamless finish, as does matching the window and door style. Alternatively, you might wish to adopt a contemporary take on the design and highlight the garage as a new element of the house, choosing a modern cladding or render.
A new cladding will overcome any issues surrounding how the old opening for the garage door is concealed — a badly bricked up opening is a
definite no no.
There is actually lots of scope for introducing natural light into a garage conversion. The wall that was once used for the garage door is the most obvious place for a new window or windows, but think further than that too. Could you include a roof lantern within a flat roof or introduce rooflights into a new pitched roof?
If the garage is located at the rear of the house or has a private outlook, consider installing sliding, French or bifold doors into one wall.
Internally, create large openings between the existing living spaces and the conversion in order to allow light to flow between the spaces. This can be particularly effective if there is only one window.
Part B of the Building Regs concerns fire safety and there are several sections covering garage conversions. You’ll need to consider the following: l “Attached garage conversions are often accessible from a hallway door providing a safe means of escape to the outside, but if you can only enter this new room from another (outer) room, it defines it as an inner room,” begins building control officer Paul Hymers.
“Because a fire in the outer room could prevent your escape, the inner room will need an alternative escape route. That could be a door or window and so the role is often performed by the one replacing the garage doors at the front. Escape windows have minimum criteria. If your inner room is a kitchen, en suite, cloakroom WC or bathroom then it doesn’t need an alternative exit.”
l In partial conversions, where only part of the garage is being used as habitable space, the wall separating the two should be fire-rated to 30 minutes.
When converting an integral, single-storey garage into living space, it is worth considering the space above it — could adding a storey above be an option? This is well worth thinking about as a way of gaining extra first floor space without increasing the overall footprint of the house.
Clearly, creating a second storey means more work and expense, but the end value of the house should make it worthwhile. The existing foundations will almost certainly need to be checked and upgraded, and there will be further Building Regulations to consider. For example, the garage ceiling and new floor in the upstairs space will have to achieve a minimum of 30 minutes fire resistance. Additionally, there will be thermal and sound insulating considerations to take into account.
Comparing insulation materials can get very technical and offers all the entertainment value of comparing insurance policies. But there are times when it is necessary to read the small print, and comparing spray foam insulation to conventional materials is one of those times.
Spray foam insulation is a bit of a Marmite product and I have to admit that it was not my favourite insulation material. But the more I learn about it, the more that I can see it has a role to play. In the right situation and installed by people who know what they are doing, it can compare favourably.
and that good thermal efficiency is not all about K value (or the subsequent U value) but also about airtightness — an argument supported by institutions like Passivhaus.
SFI is not cheap. According to Which? it will cost £20 to £50/m2, depending on thickness. The Energy Saving Trust estimates it costs around £300 to insulate the loft of a semi-detached three bedroom house, but it could cost over £1,000 to insulate the same home with SFI. £20/m2 will buy a 100mm-thick SFI, which includes installation. A 100mm-thick rigid foam insulation board will cost around £15/m2 plus the cost of installation. But the K value of SFI is closer to that of mineral wool insulation than it is to rigid foam, and mineral wool will cost around £5/m2 plus installation. But it has to be accepted that SFI saves time. This appears to be the main reason it has gained so much traction in the USA and Canada.
The higher cost of SFI is due mainly to the need to use specialist installers to do the job properly, and this has given rise to a DIY market. It is quite possible to buy the products and do the job yourself (which I have done). Part-way through the job you will realise that it is cheaper, cleaner, and far, far quicker to get the specialist in to do it. If you want to give it a go you will also need to buy all the necessary safety kit: a boiler suit, gloves, goggles and respirator. But the biggest trick will be learning how to get the foam to an even thickness, with no gaps. This is obviously important and personal experience shows that it is impossible without appropriate and extensive training.
AdvAntAges
Unlike other non-conventional insulation materials, Icynene spray foam insulation does have BBA approval and therefore can be use in compliance with Building Regulations. It is a bit pricey but used in moderation, in the right areas and in the right way it is a good solution.
Its main market in the UK is in retrofit jobs where access can be a problem. And again, in this situation spray foam can be the right solution. It should also be noted that loft and wall insulation is grant supported by energy companies — in some cases it is free. But spray foam insulation is typically not available from these sources due to its specialist nature. It is worth checking if you qualify for grant support before committing.
Foamseal foamseal.co.uk Icynene icynene.com Permaseal permasealuk.co.uk
Websters Insulation webstersinsulation.com
“Building an airtight home is not rocket science”
Richard Pender considered a number of other insulation options but in the end opted for spray foam insulation when he project managed his parent’s self-build, which is part timber frame new build, part masonry barn conversion.
“With my hands filled with the rest of the build it was a real relief to be able to offload the vast bulk of the insulating job to a single contractor who would be able to deliver at speed,” says Richard, who is now co-founder of design and build company Shawm (shawm.co.uk). Quality control and high levels of airtightness were also important. “Where hand fitted insulations are dependent on the quality of the installation, it is easy for gaps and faults to occur — on the other hand, Icynene fills every cavity,” he says. “We also liked that the depth of Icynene we were installing (approximately 200mm) would provide a first line of defence in terms of airtightness.
“We used an additional multifoil vapour control layer with the timber frame (which I would not do again) and a wood-fibre in the service void of the masonry building,” says Richard. “I was particularly keen not to use PIR [rigid foam insulation]; though its lamda value is impressive on paper it depends entirely on the quality of installation which is difficult to carry out on site.”
A specialist installer, JSJ Foam Insulation, applied the Icynene spray foam insulation, which helped to create the airtight structure for this contemporary build in Northumberland. “Building an airtight home is not rocket science, but you do need to pay attention to detail. I admit I was nervous about the airtightness testing, but we achieved 0.38 [the Building Regs’ back-stop is 10m3/hr/ m2@50Pa] first time,” he says.
The Icynene package cost around £15,000 for the 400m2 build.