This section is from the book "Safe Building", by Louis De Coppet Berg. Also available from Amazon: Code Check: An Illustrated Guide to Building a Safe House.
Timber of any kind, in walls, should be avoided, if possible. It should only be used for temporary support, as it is liable to rot, shrink, burn out, or to absorb dampness and swell, in either case causing settlements or cracks, even if not endangering the wall. In no case bond a wall with timbers. Where it is necessary to nail into a wall, wooden plugs are sometimes driven into the joints; they are very bad, however, and liable to shake the wall in driving. Wooden strips, let in, weaken the wall just that much. Wooden nailing-blocks, though not much better, are frequently used. The block should be the full thickness of the bricks, plus the upper and lower joints. If there is any mortar over or under the block, the nailing will jar it loose and the block fall out. The best arrangement to secure mailings is to build-in porous terra-cotta blocks or bricks.
Old and new walls.
Timber in walls.
"Where ends of beams arc built into the wall, they should always be cut off to a slant, as shown in Figure 74.
The anchors should be attached to the side, so as to allow the beam to fall out in case it is burned through, if the beams were not cut to a slant, the leverage produced by their weight, when burned through, would, be apt to throw the wall; as it is, each beam can fall out easily and the wall, being corbelled over the beam-opening, remains standing. It is desirable to " build-in " the ends of wooden beams as little as possible, to prevent dry-rot; if it can be arranged to circulate air around their ends, it will help preserve them. Beams should always be levclled-up with good-sized pieces of slate, and not wth wood-chips, which are liable to crush. The old-fashioned way of corbelling out to receive beams, leaving the wall intact, has much to commend it. A modern practice is to corbel out one course of brick, at each ceiling-level, just sufficient to take the projection of furring-strips; this will stop draughts in case of fire, also rats and mice from ascending. All slots for pipes, etc., should be bricked up solid around the pipes for about one foot at each ceiling-level for the same purposes. Where wooden lintels are used in walls, there should always be a relieving-arch over them, so arranged that it would stand, even if the lintel were burned out or removed; the lintel should have as little bearing as possible, and be shaved off at the ends. Figure 75 shows a wooden lintel correctly built-in. Figure 76 shows a very blundering way of building-in a wooden lintel, but one, nevertheless, frequently met with. It is obvious, however, in the latter case, that if the lintel were removed the abutment to the arch would sink and let the arch down. The relieving-arch, after it has set, should be strong enough to carry the wall, the lintel being then used for nailing only. The rule for lintels is to make their depth about one-tenth of the span. Arches are built of "row-locks" (that is, "headers,") or of "stretchers," or a combination of both, according to design. The strongest arch, however, is one which has a combination of both headers and stretchers; that is, one which is bonded on the face, and also bonded into the backing. Straight arches and arches built in circular walls should always be bonded into the backing, or if the design does not allow of this, they should be anchored back. "Straight" arches should be built with a slight "camber" up towards the centre, to allow for settlement and to satisfy the eye. About one-eighth inch rise at the centre for each foot of span is sufficient. Straight arches should never be built, as shown in Figure 77, and known as the French or Dutch arch, as there is absolutely no strength to them. Fireplaces are frequently arched over in this way, but the practice is a very bad one.
Bonded arches best.
Brick facings, as laid up in this country, usually consist of all stretchers. Every fifth or sixth course is bonded into the backing, cither by splitting the brick in two, as shown in Figure 78, and using short headers behind it, or by breaking off the rear corners, as shown in Figure 79, and using diagonally-laid bond-brick.
The latter course is the better, but there is no strength in either; particularly as, as a rule, the front brick are so much softer and weaker than those in the backing.
The English bond, in which a course of headers alternates with a course of stretchers, is much to be preferred; or, better yet, the Flemish bond, where in each course a header alternates with a stretcher. Of course, in both English and Flemish bond, if the front brick are thinner than the bricks used in the backing, larger and more unsightly joints will be necessary in front.
Figs. 78 and 79.
It is best, as a rule, not to count on the front work for strength. We frequently see masons laying up brick walls by first laying a single course of headers or stretchers on the outside of the wall, and then one on the inside, and then filling the balance of wall with bats and all kind of rubbish. This makes a very poor wall. The specification should provide that no bats or broken brick will be allowed, leaving it to the architect's discretion to stop their use, if it is being overdone; of course, some few will have to be used. But, after all, the best wall is that one which is built the most regularly and with the most frequent bonds, and no architect should be talked out of good, regular work, as being too theoretical, by so-called "practical" men. The necessity for regularity and bond is easily illustrated by taking a lot of bricks of different sizes, or even toy blocks, and attempting to pile them up without regularity; or, even if piled regularly, without bond. It will quickly be seen that the most regular and most frequently-bonded pile will go the highest. By "bond" is meant alternating headers and stretchers with regularity, and so as to cover and break joints.