The most common cause of a blocked chimney is a bird’s nest. Birds, once they have chosen a chimney that takes there fancy, will continually drop twigs down the inside and watch until they see them wedge. This can be some feet or meters down. Once a nest has been successfully built it is quite usual for these birds to return year after year. Nests can sometimes drop further down your chimney after the fledglings have departed and will normally be built up again the following year.
Removal of a nest is undertaken by pulling out and sweeping from the bottom, not from the top of the flue. If not removed your fire or stove will not operate and will emit smoke from the appliance into your house. Nests can also absorb moisture and create damp patches on the chimney breast, as well as creating bad odours.
Removal of nests can be damaging to the lining of the chimney and the prevention of further nesting should be carried out after removal.
The cost of removal varies depending on circumstances. The fitting of a good quality bird guard after the removal of a nest is recommended.
Removal of nests, can and will, only be carried out after the fledglings have departed. There are severe penalties and fines payable for removal of nests during active nesting periods.
Copies of “Birds and the Law” are available from RSPB.
Please call us for advice as to when removal is appropriate.
Creosote and Tar
Burning wood brings with it its own problems i.e. ~ the build up of tar.
As approximately 50% of the weight of a log is moisture, even in seasoned wood, it burns at a much lower temperature. Even very dry wood has high sap levels, which when burnt are carried up in the smoke, and because the temperature of the smoke is already low, the residue from the sap condenses on the sides of the flue. This build up in the flue is not as soft soot but as a ’treacle’ like substance. This comes into effect more when a wood burning stove is loaded with wood, then the air supply is shut down to maintain an over night burn. As more fires are lit in the stove it is producing more condensation, the deposits on the side of the flue turn to liquid tar “creosote”. You may see signs of this leaking down the flue pipe to the stove or around the register plate that seals off the chimney.
This moist, tar like substance will then attack the build of the chimney, and will in time, “in the case of an unlined chimney”, work its way out through into the plaster finish of the walls. A weakening to the mortar joints is common and will usually occur. The first signs of this happening show up as an odour in the bedrooms adjoining the chimney breast which is in use. Following on a darkish, half moon shape stain usually appears, and a similar one on the adjacent ceiling.
Over time the residue will build up, as it goes from its wet state to dry with subsequent fires, and so the flue will reduce in size. The solid tar is of a flammable nature and could readily catch fire. Temperatures reached in a flue during a fire can exceeded over 2000c. The result being cracks in the stack, pot, flue and plaster or a house fire. If the flue is lined, it will almost certainly destroy a steel liner, and will result in a pumice liner crumbling away. Once a fire has occurred, the volatile element of the tar is burnt, leaving a dry crumbly residue. It is therefore essential to sweep wood burning appliances at least twice per year.
Probably one of the first parts of an older property to show signs of decay and erosion are the chimney stacks. As they are mainly on top of two or three storey houses the erosion can go un-noticed for many years. Erosion to a stack can be an accumulation of many things. An incorrect mortar mix many years ago causing brick work joints and the flaunching around pots to crack or crumble. Frost, snow and rain getting into weak mortar joints. Heat from your fire, fighting with the freezing ice and frost our winter climate throws at the stack. The freeze/thaw cycle as it is commonly known can cause untold damage all brickwork. It comes as no surprise to us in the trade that the chimney stack is usually one of the first structural parts of your home that will need repair and safety work carried out on it.
If you have noticed signs of decay or damage to your stack either external or internally or need any work carried out for your household insurance due to weather damage we are only a call or email away.
Un-capped redundant chimneys can also cause the home owner many head aches. Birds and other Vermin entering your property. Birds nesting in your chimney combined with our ever increasing wet weather systems can cause untold problems with damp and mould entering into your property via your chimney. If the nests are not removed and your chimney remains uncapped and invented the damp problem will only continue to stay with you. Your chimney needs an unobstructed airflow to keep damp at bay.
Re-pointing of chimney stacks is a very good way to visually improve its appearance and the re-bedding of pots can also improve the efficiency of your fire. Re-bedding of pots and re-pointing of the stack, apart from the safety aspect, can also save on further costs being incurred i.e. pots / stacks falling onto and damaging roofs and other properties.
Clive Scott Chimney Sweeps would be pleased to help in resolving all of these problems and any Insurance work through there Chimney Maintenance Service.
For further information please do not hesitate to contact us.