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Property Defects - Fireplaces, Chimney Breasts and Flues.

Monday, 28th March 2011 | by: Peter Barry

Some time ago we wrote a post on chimney stacks, highlighting some of the common defects that we find when carrying out Building Surveys and Homebuyer Reports.

We thought it was about time we dealt with the other end of the operation and talked about the fireplaces, flues and chimney breasts inside the building and how these are connected to the chimney stack above roof level.

Before we go into too much technical detail we’ll start with a very quick history of fireplaces and chimneys. Open fires of some description have always been a fundamental element of buildings in the relatively cold climes of Northern Europe, and the way in which fireplaces and flues have developed over the years has had a significant influence over the way in which we live and the design of our houses.

In the early medieval period most buildings were heated by an open fire in the middle of the floor with the smoke (or at least some of it) escaping through holes or louvres in the roof.  The ‘fireplace’ could be beaten earth or stone slabs.  This obviously wasn’t going to be very satisfactory as buildings developed, particularly if you wanted to have more than one room and preferred it not to be full of smoke.

A means had to be found of containing the fire and conducting the smoke out of the building.  Over the years this developed into what we would now consider the traditional arrangement of fireplace, chimney breast and flue.  Fireplaces were initially quite large and inefficient and were designed to burn mostly wood.  In historical terms it is only quite recently that small, fairly efficient, coal burning grates and fireplaces were developed, and it is this type of fireplace that we will generally find in the Georgian, Victorian and Edwardian houses of London.

Much of the development of this ‘modern’ fireplace can be attributed to Benjamin Thompson (later Count Rumford) who was born in pre-revolutionary North America in 1753.  Rumford was essentially an enthusiastic amateur scientist and inventor.  When he arrived in England in the late part of the 18th Century he was appalled by the inefficiency of the open fires that he found, prompting him to write as follows:-

The enormous waste of fuel in London may be estimated by the vast, dark cloud which continually hangs over this great metropolis and frequently overshadows the whole country, far and wide.  For this dense cloud is certainly composed almost entirely of unconsumed coal, —.  I never view from a distance as I come into town this black cloud which hangs over London without wishing to be able to compute the enormous number of cauldrons of coal of which it is composed.  For, could this be ascertained, I am persuaded, so striking a fact would awaken the curiosity and excite the astonishment of all ranks of the inhabitants and perhaps turn their minds to an object of economy to which they have hitherto paid little attention

As a result, he developed by 1796 a ‘modern’ and efficient fireplace and grate which came to be known colloquially as a ‘Rumford’.  Essentially he achieved this by reducing the size of the fireplace, introducing angled rather than square sides to reflect more heat back into the room and restricting the size of the flue immediately above the fireback to increase the speed of the airflow and thus improve the efficiency or ‘draw’ of the flue.  One of the advantages of Rumford’s design was that his new, improved fireplace could be built inside the large and inefficient fireplace openings that already existed in the majority of London houses of the late 18th Century.

Fireplaces continued in use well into the 20th Century and it was not really until the 1960’s that open fires were largely replaced by central heating in the majority of houses.  At this time many fireplaces were bricked up or removed and modern houses and flats began to be built without fireplaces and flues at all.

In more recent times there has been something of a renaissance in open fires and most new houses are now built with at least one working fireplace.  When we carry out Building Surveys and Homebuyer Reports these days we are often asked by the purchaser to look at the practicalities of opening up sealed fireplaces and re-using flues that may have been redundant for many years.

The strange thing is that we never really seem to have lost our fascination with fire and it is amazing how many modern houses and flats that I survey where the focal point of the living room is a dummy fireplace.
We think that’s enough of the history for the time being and we’ll turn our attention to some of the practicalities.

The majority of the fireplaces and chimney breasts that we come across will be in houses dating from the late Georgian period up to the 1950’s.  (As we’ve said above, many of the houses built from the 1960’s onwards were built without working fireplaces.)  The fireplaces, chimney breasts and flues in these properties are generally of traditional brick construction.  The actual fire surrounds are in a variety of materials.  Cast iron fire surrounds were common in the Victorian and Edwardian era and these can range from quite simple to extremely ornate designs. These tended to be superseded by the tiled fire surround in the 1920’s and 1930’s and tiled surrounds continued to be popular until the demise of open fires in the 1960’s.

In theory chimney breasts are quite simple brick constructions. If a property has only one fireplace this is also the case in practice. In the simplest case the fireplace in the living room is connected to the chimney stack at roof level by a single brick flue.  Each fireplace has to have an individual flue, however, and in a multi-storey property this starts to get complicated.  A further complication is that in a terraced house the chimney breasts are usually on the party wall and this means that the fireplaces in one house will normally back onto the fireplaces in the adjoining house.

If we take as an example a five-storey, Georgian, terraced house with the chimney breasts on the party wall, we could potentially have ten flues running through the same chimney breast! You only have to look up at the roofs of some Georgian and Victorian terraces and count the pots on each stack. This will tell you how many flues and fireplaces the house originally had.

When we look inside a period house we see what we tend to think of as a fairly massive brick structure protruding from the wall.  In most cases this is not, in fact, a solid brick structure, but a honeycomb of hollow flues.

The chimney breasts and flues in older properties were built in traditional brickwork and lime mortar and were built up as the walls of the house were raised.  It was quite an art for the bricklayer to connect the right flues to the right fireplaces and make sure that they all avoided each other. For this reason flues in older properties rarely run in a completely vertical line from bottom to top; it is normally necessary for the flues to be off-set at some point to avoid fireplaces on the floors above.

Traditionally brick flues were almost always 225mm (9”) square internally. The main reasons for this were that it was a practical size for the efficient escape of flue gases and it was also the standard length of a brick.  As I mentioned there is often a honeycomb of flues in the same chimney breast and the ‘wall’ separating two adjoining flues was generally 112mm (4 ½ “) or ½ a brick thick. The brickwork dividing two flues is also called the ‘withe’.

Traditional brickwork in lime mortar is not particularly airtight and in order to minimise any leakage of flue gases the flue was ‘parged’ or ‘pargetted’ internally as it was built.  The pargetting would consist of a fairly rough coat of lime mortar.  This deteriorates over the years and often becomes loose and cracked and can also be dislodged when the flues are swept.  It is also not unknown for individual bricks in the ‘withe’ to become dislodged over the years with the result that gases from one flue could leak into the adjoining flue.

When surveyors carry out either Building or Homebuyer Surveys they will not be able to assess the internal condition of an old flue and their report will normally contain a warning that the flue could be damaged or defective. Defective flues can be repaired by inserting a pre-formed flue liner into the flue, although this can be a relatively expensive operation in a multi-storey house.

As open fires fell out of favour it became common to remove the original open fireplaces and brick up the openings.  Although this seems a relatively straightforward cosmetic operation, it does pose a number of potential problems.  The original open fireplaces provided an efficient form of ventilation. Even if the fire was not in use the flue would promote air movement with warm air tending to rise up the flue and escape through the chimney. This helped to reduce condensation in houses. It should also be remembered that the flue is open at the top. When coal fires were being used this was not a problem as the heat from flue gases would keep the chimneys dry. If the fireplaces are sealed up rainwater can still enter the top of the flue, but there is no longer sufficient air movement through the chimney and flue and dampness within the chimneys can be a problem.

When fireplaces are sealed up internally it is important to make sure that a suitable terminal is fitted to the top of the chimney pots.  This should prevent rain entering the flue whilst still allowing ventilation. It is also necessary to provide ventilation to the flues within the building so that air can still enter the bottom of the flue and escape through the terminal on the chimney stack.  When carrying out Homebuyer Reports or Building Surveys the surveyor will check that any redundant flues are fitted with suitable terminals at roof level and also make sure that the flues are ventilated inside the house.

As we said earlier, brick chimney breasts are quite bulky and can occupy a relatively large area in smaller houses.  Not surprisingly, quite a few chimney breasts were removed when the open fires were no longer required in order to free up much needed floor space.  This is not a problem, provided that the work is done properly!

It is quite unusual for the chimney stacks to be removed above roof level, as these are often shared with a neighbouring property and the cost of erecting scaffolding and making good to the roof tiles or slates would be prohibitive in many cases.  It is more usual for the chimney breasts to be removed inside the building and for the chimney stack to be left in place.  It is important that the remaining chimney stack is adequately supported.  This can be achieved in a number of ways.  The traditional method was to support the remaining chimney stack in the roof space with steel ‘gallows’ brackets. This is a triangular bracket made up of steel and bolted to the wall beneath the chimney stack.  The security of these brackets is largely dependent on the quality of the brickwork underneath the stack; if the brickwork is very soft or loose it may not be possible to obtain a secure fixing for the bolts.

A more secure alternative, and one that many local authorities now insist on, is a steel ‘I’ section beam that sits on the load bearing walls of the house and supports the stack above. It’s worth mentioning at this point that removing a chimney breast is considered a structural alteration and it is necessary to get approval from the Local Authority Building Control Department.  If the chimney breast is on a party wall it will also usually be necessary to a serve a Party Wall Notice on your neighbours.

Surveyors will always check whether or not chimney breasts have been removed when carrying out Homebuyer Reports and Building Surveys.  If the chimney breasts have been removed on all floors it is usually possible for the surveyor to see from within the roof space how the chimney stack has been supported, or not, as the case may be!  Over the years we have seen quite a few different methods of support, ranging from text book gallows brackets and steel beams at one end of the range to odd pieces of timber and even no support at all at the other extreme. We even know of a surveyor who, after struggling to lift an extremely heavy loft hatch, found that the unsupported chimney stack had partially collapsed on to it!

Another area of potential concern is where chimney breasts have been partially removed.  For example, if the chimney breast has been removed on the ground floor, but is still in place on the first floor it may not be possible to see if the remaining chimney breast is adequately supported without opening up the floor or ceiling.  A common feature that we also see is that the original chimney breast and fireplace is still in place on the ground floor, but the chimney breast has been removed on the floor above in order to install fitted wardrobes.  This is fine in principle, just as long as you don’t light an open fire in the ground floor fireplace!

We think that really concludes our brief history of the fireplace and chimney, but we close by just summarising a few points that you need to bear in mind when looking at an older property.

- The number of chimney pots on the roof will give an indication of the number of open fireplaces that the house originally had.

- If the flues are redundant, have they been fitted with suitable terminals to prevent rainwater entering the flue and causing dampness inside the house?

- Have the fireplaces inside the house been removed and, if so, have the flues been ventilated to prevent damp and condensation occurring?

- Have any chimney breasts been removed and, if they have, are the remaining chimney breasts and stacks adequately supported? If chimney stacks have been removed, Building Regulation Approval would have been required and you should ask your solicitor or conveyance to check that all consents have been obtained if you are considering purchasing the property.

A Homebuyer Report or Building Survey will usually be able to highlight any serious issues, but obviously the surveyor cannot see the inside of the flues and it is not always possible to say whether or not flues are in working order.

Flues to open fireplaces should be swept at least once a year if they are in use and any gas appliances, such as fires and boilers, which are connected to traditional flues should be serviced at least once a year to make sure that they are safe and that the flues are working correctly.

Categories: Surveying