Your Guide to Garage Conversion Insulation Requirements

Garage insulation

Creating more space in your home can make a huge difference to your day-to-day life, but if you’ve already boarded out your loft and your garden isn’t really big enough for a conservatory, garden room or other, what are your other options?

Many homeowners have already converted their garages into perfectly adequate additional living space, which not only adds value to your property, but can also give you your own personal space for when you need somewhere quiet to work away from the kids, or for when you just want to disappear for a bit of R&R.

If your driveway has enough space for your cars and you don’t really use your garage for anything other than storage for garden equipment or power tools, then it can be a great place to start if you need some extra space. This is the ideal option when you don’t have the room for a conservatory or extension, or have a limited budget.

We are going to cover how to insulate a garage following a conversion in this article, and will discuss what is, how you install it, and most importantly, what you need to do so it complies with Building Regulations.

Building Regulations when insulating a garage conversion

Any renovation project that involves transforming an area of your home into an extra habitable space, including garages, is more than likely to need Building Regulations.

A garage conversion will require the following:

  • Insulation of the walls, floor, and ceiling
  • Add glazed windows
  • Adequate ventilation to prevent damp and condensation
  • Electricity/gas supply connecting

Garage Conversion Insulation Requirements

Regulations for Garage conversion insulation specify how much insulation is required on the garage’s walls, floor, and ceiling. U-values are used to quantify insulation. The U-values of your space’s walls affect how much energy is lost through them. Watts-Per-Metre-Square-Kelvin (W/m2K) are used to calculate U-values.

Complying with Building Regulations is paramount. In order to comply with building regs for garage insulation, the U-value targets are:

  • Flat Roof insulation – 0.18 W/m2K
  • Wall insulation – 0.28 W/m2K
  • Floor insulation – 0.22 W/m2K

The minimum floor insulation for a garage conversion is dependent upon the insulation materials that you opt for. Polystyrene is the most common form of insulation and would need to be 100mm deep.

Garage Conversion Insulation Requirements

How to install garage conversion insulation

How you insulate a converted garage will be determined by whether your garage is attached to your house or not. If the garage is attached, it is most likely that the garage will be constructed in the same way as your house, making the insulation task easier.

However, if your garage is detached from your house, you may need to put in some extra work to bring the walls up to the Building Regulations standards. 

Garage wall insulation following a conversion

When starting with garage insulation, the first thing you should insulate are the garage walls. We recommend that you place a stud wall in front of the garage wall, with a gap between the two, which then needs to be filled with insulating material to prevent heat loss. Spray Foam, Rock wool or solid (PIR) insulation boards are often used as insulation here.

When converting your garage, you must decide what you intend to use it for, and whether part of the garage structure will remain as garage space. If you want to partition the space, you’ll need to construct a partition wall and insulate the gap between that too.

If your garage is connected to your house, and the property was constructed after the 1920s, it is likely that it has a cavity wall. Similar to a stud wall, a cavity wall already has a gap between the two walls. If this is the case then all you have to do is hire a professional insulation contractor who will fill the wall cavities with insulation.

Alternatively, if it is a solid wall construction without any wall cavities, your wall insulation solutions might involve the installation of internal wall insulation or external wall insulation.

Depending on your use for the new garage conversion, you may have need to replace your old garage door opening with walling, windows and a door. Your new walls will need to be constructed and connected to the existing walls and then adequately insulated to stop damp and moisture getting in. New double glazed windows and doors will enhance the thermal efficiency of your converted garage.

Insulation for Garage Conversion Roof

Once you have insulated the walls of your garage conversion, it’s time to focus on insulating the roof. How you approach this will depend on whether your garage has a pitched or flat roof.

A pitched roof is quite straightforward to insulate because it is insulated in the same way that you would insulate a loft space. You must exercise caution, however, if you have a flat roof.

A flat roof, particularly one on a garage, is not completely flat. In fact, any roof with less than a 10-degree slant is considered flat, so make sure that you always take precise measurements.

Once you have taken your measurements you have two options to choose from when insulating your garage conversion roof:

A cold roof — This option is when the insulation is installed between the joists of the roof.

A warm roof — This option is when the insulation is installed above the joists of the roof and has an additional waterproof layer.

We would always advise that you opt for warm roof insulation to ensure that your garage conversion is fully protected from the wet weather conditions experienced in the UK.

If your garage conversion has a flat roof, we would recommend getting a professional on board as the insulation is usually much more difficult to install on a flat roof than on a pitched roof.

Insulation for Garage Floors

The final stage of insulating your garage is the floor insulation. You should ensure that the concrete floor space is level to prevent gaps. If it needs levelling out, you have to ensure the concrete is dry before insulating the floor.

You may need to upgrade the existing garage floor so it has adequate damp protection. Damp protection can be provided by a vapour barrier or damp proof membrane.

There are two options for insulating your garage floor:

  • Installing rigid foam insulation panels across the whole floor OR
  • Create a floating floor by installing wooden sleepers and inserting foam panels between.

While covering the floor with rigid foam insulation is the easiest option, the second option also works really well.

If you plan on using the “floating floor” method, always ensure that the wood is treated before you install it, so it doesn’t become vulnerable to insect damage and decay from wet weather. Once this has been done you can lay boards across the floor and secure it.

Garage conversion summary

Garage conversions offer potential to maximise your living space and can add real value to your property. However, any conversion needs to meet building regulations, including all aspects of insulating the converted garage space.

Choosing the right garage insulation materials will ensure that you have a new space that is usable year-round, whether it is being used as an office, gym, or some other utility space. Staying on the right side of regulations is vital if you are not to face any issues with your garage conversion further down the road.

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