Flues In Voids Deadline

From 1st of January 2013 all flues in voids will require inspection hatches to inspect all joins in the flue. There will be an automatic "At Risk" added to the report even if the appliance and flue pass all checks.

An "AT RISK" added to a gas safety report means we would ask your permission to turn the appliance off.

What is a 'Flue in a Void'?

A flue in a void is where the flue (basically an exhaust pipe), instead of running straight out of the back of the boiler, through a wall and outside, it has to travel through other rooms first within a void (so via a wall, ceiling or floor).

This only applies to flues that have fans in them to push the exhaust fumes out, some do not have this and rely on natural ventilation and draughts.

Inspection hatches

Along the length of the flue there now needs to be a way of checking the inside to make sure all is well, 30cm square (12") inspection hatches need to be fitted close to every join, not more than 1.5 m (60")

That way subsequent Gas Safety engineer can make sure there are no Carbon Monoxide and other poisonous gases leaking around the joins.

Flues in ceiling spaces

There is some important advice for consumers who have flues which run in ceiling spaces:

Some properties, mainly flats and apartments, have been built with boiler flues which cannot be inspected because they are hidden behind walls or ceilings. The boiler flues that this information relates to are connected to room sealed fan assisted boilers. If you live in one of these homes then please read on for more information so you know what to do.

Gas Safe registered engineers need to be able to see the flue - which take fumes away from the boiler - as part of essential safety checks whenever the boiler is worked on. A flue in poor condition, combined with a boiler that is not working properly, could put you and your family in danger from carbon monoxide poisoning, which can cause death or serious injury.

If your boiler is situated on an outside wall, it is unlikely you have this type of flue. Alternatively, if your engineer can see all of the flue, you will not need to take any further action in relation to this matter.

If you do have a boiler where all, or part of, the flue cannot be seen, you, or your landlord, will need to arrange for inspection hatches to be fitted. This does not mean that your flue system is suddenly unsafe.

Carbon monoxide alarms are not an alternative to being able to see the flue and you will still need to have inspection hatches fitted. It is recommended that inspection hatches are fitted as soon as you are able to do so. From 1 January 2013, any Gas Safe registered engineer will turn the boiler off, with your permission and formally advise you not to use it until inspection hatches have been fitted in appropriate places.

Although most of the affected boiler and flue systems are relatively new (installed since 2000), the risk of faults leading to the release of carbon monoxide increases as the system gets older, especially if it is not serviced regularly. It is important that you have your gas appliances serviced annually.

You need to take action now

  • If your property is less than two years old then contact your builder.
  • If your property is between two and ten years old contact your home warranty provider, as you may be covered by them if there are defects in the flue. A list of the main home warranty providers is shown below. If your property is 10 years or older you should contact a Gas Safe registered engineer.

If you are a tenant, it is the responsibility of your landlord to ensure that inspection hatches are installed and that the boiler and flue are checked every year.

Guide lines for installation of hatches

  1. Should the flues be installed within boxing ins / bulkheads whether they be horizontal or vertical and be of a cosmetic nature they are likely to consist of a timber framework with a single skin of either ply/mdf or plasterboard they would not therefore require fire rated hatches therefore we can install the plastic or metal None Fire Rated type.
  2. Should the flues be within a void / ceiling consisting of 1 layer of plasterboard either fixed direct to joists or on to a metal or timber framework this would not achieve a fire rating therefore we can install the plastic of metal None Fire Rated type
  3. Should the flues be installed within a service void then we can install the plastic or metal None Fire Rated type.
  4. Should the flues be installed within boxing ins / bulkheads whether they be horizontal or vertical and consist of a timber or metal framework with numerous layers of various types of fireline / soundbloc/ plasterboard they would therefore require fire rated hatches therefore we can install the metal Fire rated type only.
  5. Should the boxing ins be concealing the flue that runs from a boiler in one property through the adjacent property before exiting out of an external wall / roof then this is likely to be a fire compartment then we can install the metal Fire Rated type only.


Unfortunately it will not be until we cut out the opening that we can truly identify whether the boxing/ceiling is either cosmetic or fire rated.

However from my experience of flat/ house conversions, new build houses and flats the boiler would be part of the second fix and the ceilings and walls would already be installed and therefore if the boiler flue doesn't go straight out an external wall directly behind or above but goes out at another position then the boxing in of the flue would be done more for cosmetic reasons.


Legal Requirements: Initial installation and inspection annually for landlords.

Recommended: Initial installation and inspection annually for home-owners.


Gas engineer to oversee position of hatches and release final report:
£40ph plus VAT per hour. (£48.00 with Vat)

Expert contractor to install hatches with correct size and strength of
hatch: £35 plus VAT per hour. (£42 with Vat)

Total cost: £75.00 P/H (plus VAT) Labour plus price of hatches. (£90.00 with vat)

Hatches cost:

300 x 300 mm plastic hatches non fire rated (None fire rated) £17.00 plus VAT each
300 x 300 mm metal hatches non fire rated (None fire rated) £37.00 plus VAT each
300 x 300 mm metal hatches fire rated (Fire rated) £76.00 plus VAT each

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