Repairing Exterior Walls: Damp-Proofing and General Repairs

Damp-proofing:

Most handyman jobs to exterior walls consist of repairs and maintenance, to prevent the entry of damp. The joints between bricks should be inspected periodically and any decayed pointing should be raked out and replaced with new pointing, as explained in describing pointing chimneys. Any cracks due to minor subsidences should be raked out and the joints filled with new mortar. If there are any persistent damp patches in the inside walls of the house, these may be due to outside defects, such as porous bricks.

Protection against entry of damp may be afforded by coating the outside bricks with a bituminous damp-proofing compound or facing the bricks with a thin layer of concrete, and this protective coating is known as rendering. A good mixture for the concrete is one part waterproof cement to three parts sand. The dry ingredients should be riddled through a sieve of fine mesh, before adding water, and the minimum amount of water only should be added to make the dry ingredients workable.

The wall surface to be rendered should be prepared by raking out the joints and brushing the wall surface with a wire brush. After this the area undergoing treatment should be thoroughly wetted with water. The concrete is spread on the wall surface with a float. If the job is a small one it is not necessary to go to the expense of purchasing a metal float and a simple float can easily be made from a piece of smooth flat wood to which should be affixed a simple wooden handle.

A hawk is used with the float to hold the concrete near the surface under treatment. The layer of concrete need only be a very thin one, and in order to finish with a smooth workman-like surface, thin pieces of wood should be fixed to the wall — builders’ laths are quite suitable for this purpose. The freshly mixed concrete is well spread on the wall surface between the wood battens with the float; finishing is done with a screed — a wooden straight-edge — which is worked over the surface of the concrete with a see-saw movement and with the edges of the screed resting on the piece of wood.

The surface may then be finally finished by dabbing it with a scrubbing brush or smoothing it gently with the float. To smooth a flat concrete surface is something which requires some degree of skill, but the handyman of average ability will soon get the feel of the job, after a few trial attempts. The secret of successful finishing lies in the use of the minimum amount of water when mixing the rendering. The top edge of the rendering should be finished to slant downwards and outwards. Damp-proofing to outside walls may also be effected by coating the surface of porous bricks with a cement paint.

Repairs to Damp-courses:

cross-section of wall-baseOne of the most general causes of damp in walls of a house is due to the failure of the damp-course, and brief references to damp-courses have been made Damp Walls: How to Treat and Repair Them. However, to clarify the instructions about damp-courses, a cross-section of a typical wall is illustrated (right). This shows the base of the wall with concrete foundation on which brick footings, are erected before the wall proper is built. The wall of a house consists of two separate walls, or skins, between which there is a cavity. At the base of the wall, above the footings, is placed a layer of damp-proof material. This may be slate, tar or bituminized felt. This layer of material is known as the damp-course. The function of the damp-course is to prevent the rising of ground moisture from entering the structure of the house. Obviously if the damp-course does become damaged, it will fail and water will be permitted to enter the structure. It has been previously discussed in the instructions for dealing with dry rot, that the damp-courses are sometimes short-circuited by rock gardens or flower-beds piled against the walls of the house.

A damp-course should reasonably last the life of the house, but should there be any damage to the course, it will be necessary to renew it, by cleaning out the joint and inserting new damp-proofing material. This is a very fiddly job, and one which should be carried out very carefully and thoroughly to obtain full protection. Only a small section of the wall should be dealt with at a time, and the ends of joining sections of the damp-course, which may consist of one layer of bituminized felt, or two layers of slate, should overlap.

General Exterior House Repairs:

The outside woodwork of houses should be inspected at regular intervals, and any ageing paint surfaces should be recoated before adverse conditions have a chance to attack the woodwork. Special attention should be given to the edges of the windows and door frames. Any decayed or crumbling joints between walls and wooden framework should be hooked out and replaced with pointing mortar. Dried and decayed putty around window-frames should be replaced with fresh putty.

Outside metalwork should receive special attention. Any rusted metalwork may be treated with a special rust-proof compound. The preparations consist of cleaning any loose particles from the surface with a wire brush; the rust-proofing is then painted on the metalwork and it oxidizes the old rust and prevents the formation of new rust.

 

20. July 2011 by admin
Categories: Construction, External Repairs, Walls | Tags: , , , | Comments Off on Repairing Exterior Walls: Damp-Proofing and General Repairs

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