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Cold room above a garage or carport?...Solutions here..

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Do you have a room above a garage or an outdoor area (such as a carport) that is difficult to keep warm?

This article describes of a range of practical actions you can take to improve comfort and reduce costs in these sort of situations.

I've included very practical guidance as many of these things can be done as a DIY job.

This isn't the easiest problem to solve. The suggestions here aren't perfectly thought through for every set of circumstances but I hope they help you in some way.

You may need to adapt some of these ideas, solutions and methods to suit your own situation.

The actions and quick links to them are:

Rooms over car ports can suffer the same problems

The facts

Current building regulations require insulation to be fitted in the ceiling above a garage if there is a room above. For many years, this was either not required or only a minimal amount of insulation was required. As a result, there many integrated garages in the UK with little or minimal ceiling insulation. The current recommendation is around 140mm of insulation.

A garage is effectively a cold 'outdoor' room. If it has minimal or no insulation in the ceiling, rooms above can often be difficult to heat or always feel colder than other rooms upstairs.

Garages are also usually very draughty. These draughts can often find their way into rooms above through various gaps and cracks. This can even be the case for garage ceilings that are already fully insulated. Insulation generally doesn't stop air movement.


Common examples of draught sources

Upstairs rooms often have gaps around the edges of the skirting boards or between floor boards, as shown in the photo below. Cold air will seep into the room from the garage below through these edge gaps. This will be true even if you have well fitted carpet.

This thermal image below of a bare floor shows how cold air enter a room where there is no floor covering. The blue areas are cold air coming through from underneath.

Draughts through floorboards
Courtesy the Cheese Project Bristol

This thermal image shows how draughts infiltrate at the edges, even though the gap is very narrow. A gap is a gap and air will find its way through!



There are a range of solutions. I'll start off with some easy ones that will certainly help improve the situation. I'll then move onto solutions that require more effort but will make a bigger difference.

Important safety point

The actions I am describing below are likely to reduce the ventilation in the room (s) above the garage. If you have any form of unvented combustion heater in the room you want to make modifications to, such as a gas heater it is ESSENTIAL to ensure that there is still adequate ventilation in the room for the appliance being used. This is to prevent the build-up of poisonous carbon monoxide gas.

If in doubt about whether there will still be adequate ventilation, seek advice from an appropriate professional.


Action 1 - Draught-proofing gaps at room edges

This was something I did on a problem floor of my own a few years ago and made a big difference. It is very simple, easy to do and very cheap to do (under a tenner). In my case I had really big gaps at the edges of the floor area and the room was never warm.

To draught proof the edges I pushed some old newspaper into the gap with a wallpaper scraper blade (as you can see the photo below). This does a pretty good job of filling the gap and keeping cold air out.

If your gaps are too narrow to squash newspaper that is a bonus! You can go straight to the next sealant stage below.

The next stage is to use a flexible sealant to seal over the newspaper.

Newspaper will do a great job on its own, but it will help further if you use a flexible to completely close off the gap. This will also leave a more attractive finish.

This inexpensive decorators caulk is a perfect sealant for the job. You'll need a sealant gun to extrude the sealant and if you don't have one, get one of these. If you've never used a sealant gun, this 2 minute YouTube video explains how. There are other YouTube videos on using sealant guns if this one doesn't give you enough confidence to have a go.

The sealant is simply squirted into the gap as shown below.

If you find the sealant is going everywhere, don't panic, just reduce the pressure on the trigger to reduce the flow. The sealants suggested above can easily be cleaned up with a damp cloth.

(Please excuse the state of the floor and skirting board in these photos. This skirting board is inside a built-in wardrobe at home that we've yet to decorate!)

Smooth over and squidge the sealant in with a finger. If the carpet grip rods are in the way, use the wallpaper scraper shown above to do this rather than your finger, so you avoid the sharp pins on the grip rods.

This YouTube video is of a very cheery Australian lady doing much the same thing as I've described above showing you how to use the sealant gun. She doesn't use newspaper but uses a product specifically made to do the same job. Everything else is the same as my method above.

If messing about with sealant to seal the edges isn't for you here is a plastic strip product you can use as an alternative.

Lifting carpets

To do the above you will need to lift the carpet at the very edges of the room.

There are very few YouTube videos on how to lift a carpet, but here is one that at least shows you how to get going.

It may be necessary to lift the carpet grip rods if they're too close to the skirting board to do the job. The pins on grip roads are wickedly sharp so beware. Grip rods can easily be nailed back down if do you have to remove them.

If you have built in furniture

Built in furniture can often be a route for draughts to come up from the garage below.

It sometimes needs DIY creativity to fix draughts in this situation.

Chests of drawers such as the ones below are often the biggest (but not only) source from behind this sort of furniture. The drawers usually lift out very easily to give you access to become a draught detective and work out what you need to do to nail it.


Action 2 - draught-proofing gaps between floor boards

This action requires a chunk more effort.

It only applies to you if you have wooden floor boards like those shown in the picture below. If you have chipboard floors you typically won't have gaps like these.

Here we use a similar sealing method to the one I used above. In this case it is to seal the gaps between the wooden floor boards themselves. These gaps can be really wide in some houses.

This means gaining access to the floor area itself.

Depending on the room shape and size and how much furniture it contains, you might be able to complete this task without emptying the room.

The ideal is situation is if you can move furniture around and lift the carpet one part of the room at a time and do this job in stages.

Emptying the room completely and lifting the carpet is obviously more effort but might be necessary in some situations.

In my experience, if you lift and refit a carpet yourself, they refit reasonably well though never look quite as stretched and flat as when they were originally fitted.

Use plenty of sealant to fill gaps between the boards.

For these cracks I recommend a different sealant. one that is generally called a "frame sealant". It's applied in the same way as decorators caulk above but is more durable. Here is an example product.

If you have large gaps between floor boards you can always partially fill the gap first with newspaper just as I showed in Action 1 above. Partially fill big gaps with stuffed newspaper to reduce the amount of sealant you need to use.

Be prepared for some ugly sights though when you lift carpets in older homes.

The images below show the sort of draughty gaps that can lurk beneath carpet. A little DIY creativity is required to fill.

Cardboard or a thin piece of plastic can be cut to fit cover the gap and stuck in place would probably do. Whatever you do, it doesn't need to be particularly strong - just whatever works well enough to cover the gaps/holes and keep the cold air at bay.

An example solution - this takeaway container lid can be cut to size and shape to fit around the pipe and then stuck down with sealant.

Alternative method to filling gaps between floor boards

If using sealant to fill floor board gaps feels a bit too messy then here are some other options:

Stopgap product - This is a flexible plastic strip that you cut to size and fit by hand.

It is very quick to use, but more expensive solution, at around £25 a roll. You can find it here on Amazon (and you will probably need more than one roll). Here is the manufacturer website. It includes a a short video which explains how to fit the product.

The advantage of this solution is no mess, and you can put floor coverings straight back down although in my opinion it won't seal as well as sealant.

Draughtex - This is a rubber product that you insert into gaps. It comes in variety of thicknesses for under £30 for a 40 meter roll. More info here.


Action 3 - upgrading to highly insulating underlay and carpet

The choice of floor covering in the room above the garage can make a BIG difference to how cold a room above a garage will feel.

Carpet and underlay CAN provide very useful layers of insulation and can significantly improve comfort in the room. The insulating properties of carpet & underlay vary widely

We are probably all familiar with the TOG system used for duvets to tell us how warm they are going to be. Higher TOG duvets are much better insulators than lower TOG duvets.

The carpet and underlay industry use the same TOG system to tell you how good an insulator carpets and underlays are. The higher the TOG, the better insulating the carpet or underlay is.

Carpet underlay

The traditional green rubber underlay you see here have a TOG rating of less than 1.5.

Compare this with a summer weight bed duvet, which typically has a TOG rating of 4.5.

This tells us very clearly that this underlay isn't going to be a particularly good at keeping heat in.

There are many budget underlays that are even poorer.

TOG information is easy to find in product information when searching for or buying underlay.

If you have a thin or low TOG underlay you could invest in one with a HIGHER TOG rating.

There are many to choose from with TOG ratings as high as 3.6, This is much more like a summer weight bed duvet.

The best I’ve found, and one I have used in several rooms myself, is one made from 100% recycled wool (example shown below).

This type of insulation has been around for many decades, is very eco-friendly and hard wearing. It also has excellent sound insulation properties and feels lovely under foot. The thicker the better. These types of underlay can be as thick as 18mm and are typically cheaper than modern synthetic underlays.

There are numerous manufacturers and sellers online with very similar products but here is one example.

Working out the TOG rating of your existing underlay

You probably won't know the TOG rating is of your existing carpet underlay do you won't know if it is worth upgrading it.

It might not be too hard to identify though. The Carpetright website has a big range of underlays with good pictures of each one and associated TOG information.

If you lift a corner of the carpet and look at the style and thickness of your existing underlay. Take a photo of it, measure the thickness and see if it matches any of the products on the Carpetright website.


Carpets TOG ratings also vary a lot ranging from 0.7 to 3 TOG.

So, to give you a better insulated floor, it is possible to have carpet of 3 TOG on top underlay of 3.6 TOG. Add the two figures together and you have a total TOG rating of 6.6 for your floor coverings, much better than a summer weight duvet.

This will not be as good as having a properly insulated garage ceiling. In my experience though it should give a noticeable improvement if you currently have low TOG value floor coverings.

Upgrading to a higher TOG carpet is obviously a costly step. It might be something you keep on hold as an idea consider when you next replace the carpet anyway. The highest TOG carpets are likely to be wool carpets which are usually the most expensive.

If you currently have laminate flooring

Laminated or wood flooring is a poor insulator. High TOG carpet and underlay are clearly going to be much better.

Working out the TOG rating of your existing carpet

Identifying the TOG rating of your existing carpet might be harder than identifying the TOG of your existing underlay.

You'll have to do some legwork and visit a carpet showroom to look at different carpets, their TOG values, and compare to yours at home to work this out.


Action 4 - Simple DIY actions from underneath

Draught proofing ceiling

One small but effective thing that CAN be done from underneath is to identify gaps in the garage ceiling into the space above. These are likely to be at the edges round plumbing or electrical cables or that disappear into the space above.

Some garage ceilings can actually be quite well sealed. The one below clearly isn't.

These gaps should be sealed with a fireproof sealant, (often referred to as Firestop). Here is an example of one of these products.

Insulating and draught proofing the garage door

These are DIY jobs.

Insulating. There are a number of products and solutions to insulate the inside of a garage door. A number of them are reviewed on this site.

If you have a south garage that gets hot in summer, insulating the door will help reduce how hot the garage gets. This will in turn reduce how hot the room above gets.

Draught reduction. If you have a gap under your garage door there are many different products out there that can substantially reduce draughts into the garage. Reducing draughts INTO the garage will reduce draughts into the room above and make the garage warmer. This is just one of the products on the market.


Action 5 - DIY insulating the garage ceiling from the room above

From my experience, the above actions should make a noticeable difference to comfort and retention of heat in a room.

By far the best solution though, is to insulate the space between floor of the room and the garage ceiling below.

A first step is to investigate how much insulation might be in there already, by either

  • Drilling an appropriate sized hole in the ceiling below to inspect. Bear in mind the risk of electrical cables being where you are drilling and consider turning the power off while drilling any inspection holes.

  • Lowering a ceiling light fitting if you are competent ans confident to do so, and inspecting through the hole where the lights cable comes through.

Installing a decent amount of insulation in this space can provide around 5 times as much benefit as the high TOG carpet/underlay actions above.

This is obviously more disruptive to do.

Insulating from above can be done as a DIY job, by lifting some areas

If you have tips or ideas to help improve what I've written below do shout.

First though - how to lift floor boards if you have never done it

Both methods below mean lifting some floor boarding to gain access to the space below.

For a couple of different YouTube videos on how to lift traditional floor boards see here and here.

If you have chipboard floors this is tricker, messier and needs more DIY expertise. This online video has the basics and this one is also very helpful (see from 5 mins 40 seconds onwards).

Important safety points

If you have any electrical cabling under the flooring you intend to insulate, it is incredibly important to understand what those cables do. In some situations, especially in the case of high-power cables (such as cables for cookers, immersions, storage heaters, showers) it may be important to keep insulation away from these cables altogether to avoid any risks of them overheating. If you are in any doubt, seek the advice of a qualified electrician.

Follow any guidance on the insulation product you use about the need to wear goggles or a face mask.

Insulating under the floor with rockwool

Rockwool is the glass mineral wool insulation that is commonly used to insulate lofts and is an inexpensive solution.

It's recommended you have a layer of 140mm or more of this installed in this application. The depth of joists is usually 200mm or more, so you can go thicker than 140mm if you wish.

Image from

You will need to lift at least one floor board down the middle of the room so you can feed the insulation underneath as you can see below. You will probably need lift two floor boards adjacent to each other to create a big enough gap.

You'll need find something flexible to use as a 'pushing or stuffing rod' to push the insulation all the way into the floor space. An old plastic curtain track or something similar would be ideal.

This sort of insulation works best if it isn't compressed so don't stuff it in too firmly. You want the space to be full of light, airy and fluffy rockwool.

Here is an example from B&Q of a rockwool product that would probably suit many situations, providing 200mm of insulation.

For a room with an area of 20 meters 3 rolls of this stuff might be enough. That would work out around £75 in total.

If there is a lot of rubbish under there that will prevent the insulation from sliding along nicely then it needs clearing out.

Underfloor spaces will all have diagonal cross braces between floor joists from time to time, such as those shown in the photo below. Depending on where these are, you may need to lift more floor boards to get good enough access to all the floor area.

Cutting rockwool insulation to the right width is really easy as this video shows. You can buy special knives for it but it can even be done with a bread knife.

If when you come to do this job you find you already have SOME rockwool under there this will make this a fidlier job. It might be best to extract the existing stuff, and combine with your new rockwool and refill the cavity with a thicker combination of the two.


Action 6 - Insulating the garage ceiling using a specialist contractor

If the DIY approaches above don't grab you, a very effective professional solution is now available as a service, This is to have insulation blown into the space between the garage and the room above professionally.

A company called Redplug offer this as a service. They do this by drilling a grid of holes in the ceiling from the garage below, and blowing in rockwool fibres, completely filling the space above. This video shows how they do it:

They can also do the same thing from the room above (drilling holes in the floor) if for some reason doing it from below isn't practical.

Insulating from above might be the only option in situations like this

More info on their site here. The work takes around half a day, and costs around £1000 for a single garage. The company is based in Worcestershire. They don't cover the whole country though.

I've searched widely but been unable to find any other companies offering this particular service. If you want to explore this and are outside the Redplug area I suggest you contact some local cavity wall insulation companies and ask them if they know anyone in your area that does this sort of work.


More traditional garage insulation retrofit solutions used by the building trade

There are also more established methods used in the building trade for insulating a garage ceiling from underneath. These are:

  • Removing the existing ceiling boarding, fitting insulation between the exposed joists for the room above, and then replacing the garage ceiling.

  • Applying fireproof insulated plasterboard panels or equivalent to the existing garage ceiling (which also reduces the height of the garage).

In both cases building regulations would need to be observed, particularly in relation to fire safety.


I run this website as a hobby, because I care about this stuff, and do it for no commercial purpose. If you have valued the information here, please tell other people about it.

If you have any other suggestions for additions to the above, or would like to subscribe to email updates, please let me know using the contact form.



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