Hong Kong Builder
ARCHITECTS AND RATS
By Geo. W. Grey, F.R.I.B.A., F.S.I.
The medical profession states that the rat is a vehicle of many diseases; the statistician gives colossal figures for the value of the loss they cause by the quan- tities of food they consume and spoil, and by the damage they cause to property, and the naturalists give astound- ing figures of how quickly they can multiply, while any purpose, they may have served in more primitive days as scavengers, has ceased to have value, and now, the only useful purpose they appear to serve is as subjects for surgical and medical experiments.
While those connected with building may not be directly concerned in the destruction of the rat, they can in many cases tend to prevent their multiplication by building so as not to provide accommodation suitable to rat pleasures, and rat family life.
The naturalist, in works upon the rat, appears to divide them into the black and the brown rats, giving their place of origin, the peculiarities of each, with their desires in the way of abode and food.
The difference between the black and the brown rat, while of interest to the naturalist, does not appear to affect the builder greatly, it being necessary to guard against the peculiarities of both.
In addition to the food they eat and destroy, there is the damage done by gnawing.
It is reported that their attacks upon hardwoods, lead pipes, bricks and mortars, etc., by gnawing, is neces- sary on the part of the rat in order to keep the continu- ously growing incisor teeth from becoming too long, and that matter of this kind is not swallowed.
The death of an old lady by asphyxiation has been attributed to rats gnawing through a "compo" gas pipe. Attacks upon lead pipes have also been attributed to an endeavour to reach the water within the pipes, as well as the necessity of keeping the teeth from becoming too long.
The reinforced concrete building and the steel frame encased with concrete, are probably the buildings which have the least attraction for the rat.
The material is too hard for them to gnaw, and these forms of construction are leaving the minimum of spaces in which the rat can make runs.
Ordinary lime mortar does not appear to be suffic- iently hard to prevent them scraping this out from the joints of the brickwork, and making a way through a wall. While a building may be constructed to give them no place of abode, if food is stored, and openings exist which enable them to enter the building, they may make their place of shelter in adjoining buildings more suitable for their accommodation, or in heaps of rubbish, etc., en- tering the building for food when all is quiet, taking the food away to their place of shelter for consumption and storage.
Access to buildings can be prevented by closely fit- ting doors, and the avoidance of unguarded openings through external walls.
Where doors are obliged to stand open for the pur- pose of trade, and there is food which can be picked up and taken to their place of abode for consumption, if the building is free from rubbish, and in a good state of repair, so that there is no "cover" for the rat, a dog or cat should then be able to successfully keep the building free.
Drains are often a means of access to a building. Drains, in a bad state of repair, permitting rats to enter the drainage system, are a rat's paradise; drains not only affording a means of communication, but their contents also provide both food and drink.
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It is often stated that rats will not pass through a trap, such as an interceptor.
This has been contradicted by those claiming to have studied the matter, they stating that an interceptor is usually a barrier to rats, because they cannot see a light on the other side, but that if a manhole cover does not fit tightly, enabling a light to be seen through the water seal, a rat will then dive through the trap, and that, in the case of yard gullies, rats repeatedly do so.
While, with many regulations, the only inlet within the building which is permitted to a drain is the W. C., with old buildings, inlets to drains, within the building, are to be found, and where these exist in the forms of yard gullies, access by rats to the building by means of the drains is not impossible if the claim is correct that they will pass through an interceptor trap or gully, if a light can be seen on the other side.
A very frequent means of access to factories, and stores, are the outlets from the channels formed in the floor to take away water from washing.
The outlets from these channels are often through the external wall, have no grating, or are protected by a grating having large apertures; anything in excess of 1⁄2" mesh being considered passable by rats.
Channels of all kinds are an encouragement to rats. The water heating channels, so frequently found in the older Public Institutes, are often a means of com- munication from the basement in which the rat may have entered the building, and in which he may live, to rooms containing food.
Care should be taken that materials used are not
such as to provide them with a home or food.
Felt packing provides a good home, while some sound insulating materials are edible.
Rats are good climbers and fair jumpers, and may find their way into upper stories of buildings by climbing creepers, the wooden walls of outhouses, trees, etc., then jumping into the openings.
It is claimed that rats will climb rough cast. Government circulars, issued in England and U.S.A., recommend a height of 3 feet to 3% feet for granary piles, presumably assuming that a rat cannot jump ver- tically higher than this.
While it may be difficult to clear old buildings of rats, their numbers can be lessened by making their life difficult.
Like most vermin, they prefer the dark, and do not like to be seen.
If circumstances permit of it, any casings, with hol- lows behind, should be removed.
With old residences, used for storage purposes, the lath and plaster ceilings should be taken down and if there is a space under the ground floor, this filled in and covered with six inches of concrete, and this concrete paved.
Rats usually follow the same runs in their journeys to and fro. These can be traced by their droppings, and where they cross cleaned surfaces, by their foot prints.
Their holes in brickwork should be enlarged to take a new brick and the new brick set in Portland cement mortar.
Where found to climb pipe, a collar of galvanized sheet iron, or zinc, projecting about four inches at right angles to the pipe, should stop their passage.
If the site is not covered with concrete, rats may burrow down from outside, pass under the walls, and up into the buildings.