This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
When the bases of house-walls are wet, it may be found that the damp-course is either below, or not high enough above, the surface of the outside ground, or that the builder has "forgotten" to provide one. In the former case, where the ground cannot be permanently lowered, the evil may be mitigated by running a cement plinth on the outside of the wall from below the damp-course to about a foot above the ground. In the latter instance, a damp-course may be inserted by removing three courses of bricks in lengths of two or three feet at a time. This somewhat expensive and otherwise inconvenient process would perhaps only be resorted to in extremely bad cases, but it has been done.
Absence of (or defective) eaves-spouting may cause the walls to be wet above the damp-course, not only because of the water which runs down the wall, but from the splash of the drip on the pavement, or into the gutter which may have d formed by the fall.
Where basement walls are wet because of the ground outside lying against them, the ground should where possible be removed, and a drained "area" constructed.1 When this cannot be done, the evil may be lessened by cementing the outside of the wall, or facing it with a wall of tar-concrete 6 inches thick, temporarily removing the soil for the purpose, and backing up the concrete wall as it rises with the returned earth. Even a loose rubble insertion, 18 inches or so thick, between the wall and the earth will have a good effect. When nothing can be done outside, a 4 1/2-inch brick wall may be built inside, leaving a space of 2\ inches between it and the wet wall, such space to be closed at the top and ventilated from the exterior. Even plastering on laths and 1 1/2-inch battens would be an improvement, as the wet surface would be protected from the evaporating influence of the warm room, but battens in contact with a damp wall are liable to rot.
Where brick walls above ground are damp from driving rain, it is generally because they are too thin, or the bricks are not well burnt and consequently inordinately porous, or the joints have not been well filled with mortar. To lath and plaster the wall inside on battens, and repoint it outside, would effectually remove the unsightliness of stains, and perhaps remove the danger to health, but complete dryness can only be obtained by thorough painting tide, or covering the exterior with stucco and then painting it, or by slating. Damp walls are sometimes covered with matched or grooved-and-tongued boards on battens, but for several obvious reaaoss this method cannot be recommended.
The inspector should fearlessly report house-walls which are actually wet, but should hesitate where damp stains only are apparent, and in such a case only do so after the Medical Officer of Health has declared them to be so bad as to endanger health.
The upper parts of house-walls may be wet from defective eaves or eavesgutters, or because of the saturated state of the brickwork projecting above the roof, such as parapet walls and chimney-stacks. The latter fault is apparent mainly in attic rooms formed in the roof. In the former case, a fault in the coping, or the lead gutter behind it, may be discovered. In the latter, the only cure would be to take the stack down to near the roof slates, lay on a damp course of lead, and re-erect the chimneys
1 See Fig. 18, page 56,, vol i. - En.
Wet ceilings in upper rooms are of course caused by defects in the roof covering, and in searching for these it must be remembered that the fault may not be immediately over the damp spot, as rain will often trickle down a rafter some distance from the broken slate, tile, defective Hashing or secret gutter, before it drops on to the ceiling below.
When "lead-flats" have much "fall", the sheets of lead, by unequal expansion and contraction, may "creep" downwards and expose the drips, whilst in lead-covered roofs which have a decided slope, the sheets may actually slip and expose the joint at the ridge. It is unnecessary to say that defects in the lead itself, as well as bad workmanship displayed by insufficient overlap at drips and flashings, account for some leaky roofs. One house within the writer's perience, the flat roof of which was surrounded with parapet walls, was ■ perl shower-bath during severe frosts with snow. The underside of the snow was melted by the heat of the house, and the resulting water, unable to escape through the frozen gutter-outlets, formed a pond on the roof, which rose above the rolls and poured into the rooms beneath.
When the inspector notices that the boards of ground-floors are excessively curved, the edges being raised in sharp ridges, he will suspect dampness or even water underneath. He can test this by boring three or four holes through the floor-boards with a large gimlet (having first gained the consent of the owner or occupier), and passing a thin iron rod - a stair-rod will do if it is long enough - down into the soil beneath. The holes may afterwards be stopped with wood plugs. If he is not satisfied with the result of this trial, he should get underneath the floor if the space permit, and make a thorough examination. If there are no means of access already provided, he can, with the permission of the occupier, cut through three or four hoards between a pair of joists. The pieces of floor-board so removed may be replaced after nailing a cleat or fillet to the side of each of the exposed joists. The only tools needed for this operation are a gimlet and a keyhole saw. The nails and pieces of wood for cleats are usually to be found upon the premises.
Flags or bricks laid directly upon the ground are generally damp, the dampness being more apparent under an impervious covering, such as oil-cloth or linoleum, than upon floors which are uncovered. A thick layer of sand or ashes upon a bed of broken bricks underneath the flags or tiles will often remedy the evil, and if the floor is above the surface of the ground outside, this foundation may be further improved by embedding in it air-drains of agricultural pipes, open at each end, behind a perforated brick in the outer wall of the house. Flags may also be laid upon dwarf walls covered with elate, and ventilation provided underneath.
Where floors are below the outside surface, air may be admitted to the underside by forming a flue in the thickness of the outer wall, opening at the bottom under the floor, and at the top into the outer air, as shown in Fig. 668.
Dry-rot under wood floors is favoured by dampness and want of ventilation, the provision of ample ventilation alone often removing the dampness and killing the fungus when the latter is in the earlier stages of its growth. A musty. mushroomy smell will arrest the attention of the inspector where this pest is present, and on raising the edges of the carpet, fine filaments of the plant may sometimes be seen on the top of the floor-boards near the skirting. In neglected and bad cases, large fungi may appear at the margins of the floor when the room has been closed even for a few days, and often quite a cart-load has been removed from beneath a floor so affected. When the evil has reached a bad stage, nothing but the entire removal of the floor, washing the bases of the walls, and saturating the ground-surface with hot lime, will eradicate it.
I by-rot is probably more to be feared when the house is built upon "made" ground, which often contains vegetable or even stable refuse. Its presence, therefore, should lead to the suspicion of this being the case, and the further precaution should be taken of covering with cement concrete the whole surface of the ground, after liming and before laying the new floor. There are, of course, strong reasons why the surface of the ground under houses should be covered with cement concrete even where "made" ground is not present, but this has already been dealt with elsewhere in this book.
Fig. 668. - Air flue for ventilating Floor below Ground.