BRICK CHIMNEYS CAN BE EFFICIENT AND SAFE

Press, Volume CVI, Issue 31349, 20 April 1967, Page 26

BRICK CHIMNEYS CAN BE EFFICIENT AND SAFE

Many New Zealand homes have a chimney and fireplace, even more recent homes having forms of central heating have incorporated open fires as a visual comfort and as a focal point of winter-living for the family.

There are many methods of achieving satisfactory construction of fireplace and chimney, and we can most usefully factors leading to a sound and efficient construction, factors leading to a round and efficient construction.

New Zealand has a high earthquake risk and this must be taken into account when j designing and building chimneys.

Further the introduction of new types of domesticheating appliances, namely the slow combustion stove, has created problems of flue or chimney design not previously experienced. These are mainly because of the high temperature of the gases passing from the stove to the flue. These temperatures occur because, unlike an open fire, there is no large movement of cold air across the fire-bed to cool the gases before they reach the chimney. Bricks have been used for many years for all types of chimneys. Both industrial and domestic chimneys were built of brick long before the discovery of Portland cement Research and experience have not only

Improved the brick and the clay flue-liner, but the knowledge of mortars and good construction techniques today result in the erection’of sound, long-lasting chimney structures. Chimneys located on inside walls will reduce construction costs by saving of both materials and labour. The efficiency of the chimney will be increased as it is protected from extreme cold, it will not cool so quickly and better draught will be maintained. The heat of the chimney will also help to warm rooms through which it passes. However, because of the design of minimum area rooms there is a tendency today to locate the fireplace and the chimney on outside

walls and thus reduce the intrusion of the fireplace and chimney into the small spaces. In such cases as these, extra thickness in the chimney walls and the use of insulating materials do much to increase efficiency. Care should be taken in the planning of a fireplace so that there is ample, unobstructed wall space on each side as well as floor space in front Openings such as doors and windows in the fireplace walls should be avoided. A chimney is considered to be part of a “construction” or a structure itself, therefore it must comply with requirements of the local authority by-laws. These vary throughout New Zealand and some local bodies require that all chimneys, irrespective - of type, must be reinforced, while others permit brick

chimneys to be built without reinforcing. It is common in New Zealand to use firebricks as the fireback in fireplaces, although in some areas precast sectional, refractory firebacks are available. Because of the temperature in the fire bed it is advisable to use special mortars for the fireback. These mortars may be a mortar using aluminous cement and buff or other colour brick grog or an airsetting refractory mortar of a proprietary manufacture. Most air-setting refractories are supplied together with instructions for use, and these instructions should be followed. Ordinary Portland cement mixtures should not be used where the temperature of the concrete or motar is likely to rise above 300 deg. Centigrade.

Therefore, where combustion stoves of the enclosed type are being installed it is preferable to use special mortars in the lower parts of the flue near the inlet from the heaters.