Building House Walls
Walls are usually either of brick, stone or the other materials which have already been briefly discussed in exterior wall ideas.
They should as far as possible have non-absorbent properties which can be tested by placing the material in water and weighing before and after immersion, so that the amount of water absorbed can be ascertained.
This absorption varies considerably with different materials, as seen in the approximate table given below :
Granite absorbs 1 per cent of its weight; Blue Staffordshire bricks, 6 per cent; Ordinary London stocks; 7 ½, Hard stocks, 10; Portland stone, 14; Bath stone, 17
A brick backing not less than nine inches in thickness is generally placed behind all stone walls, and care should be taken that this backing is thoroughly bonded with the stone facing, one through stone for every square yard of wall surface usually being sufficient.
Hollow Walls. Hollow walls are useful in exposed situations, the two portions forming the inner and outer walls being placed about 2½ in. apart and connected together with bonding bricks or metal wall-ties at intervals, as seen in picture 23.
Authorities differ as to whether the one-brick or the half-brick wall should be placed externally, and there are advantages in both methods ; although it seems better .construction to put the half-brick wall outside, so that the floor and roof timbers can rest on a solid one-brick wall as shown in picture 23. The vitrified bonding bricks which are sometimes used to bind the two thicknesses together should be of the form shown in picture 23, in order that rain may not be drawn from the outer to the inner wall, and so nullify the advantage gained by having the cavity.
Picture 23. A Hollow Wall.
Picture 23 also shows how the head and sill of a window in a hollow wall should be protected from any damp which may find its way into the hollow space.
Wall Facings. Brick walls, especially on exposed sites, are often protected from driving rains by being rendered in cement, which, although not always satisfactory in appearance, is certainly effective.
Rough cast is also used for this purpose, and if applied with simplicity and taste, forms a very pleasing and effective resistance to the damp.
The following is a good specification for pebble-dash rough cast in two - coat work. The first or backing coat is composed of two parts of cement to five of pit-sand, but more cement is required for a hungry variety of sand; and the finishing coat is composed of 6 parts of selected pebbles, 1 ½ of cement, ½ of sand and 1 of slaked lime, the total thickness on the walls being about ¾ in. Other varieties of rough cast are formed with the surface left rough from the trowel or treated with a stiff broom, to give it texture. The whole may with advantage be brushed over with a wash made in the proportion of 28 Ib. of boiled Russian tallow to 36 gallons of yellow ochre and slaked lime.
Weather tiling, as shown in picture 24, is an excellent method of keeping walls dry against driving rains (see Exterior Wall Ideas).
Picture 24, Wall Tiling.
Next: Damp Proof Courses.