When a chimney is damp, examine the flashing at the junction with the
roof, especially if wet spots appear on the ceilings of rooms. Methods of
repairing flashing are given in Farmers' Bulletin 1751, Roof Coverings
for Farm Buildings and Their Repair. If the flashing is sound, possibly
water runs down the inside of the flue and through defective mortar
joints. Where these cannot be reached readily, the chimney may have to be
torn down and rebuilt. Sometimes a hood (fig. 18, _A_ and _B_) is built
on top of the chimney to keep out water or to prevent wind blowing down
it. To prevent dampness being drawn up from the ground, the mortar can
be raked from a joint at least 12 inches above the ground and a layer of
slate, asbestos shingles, or rust-resistant sheet metal and new mortar
worked into the joint. This work should be done by a mason. If bricks
are porous or eroded, raking out the mortar one-half of an inch deep and
applying three-fourths of an inch of cement plaster to the surfaces is
effective. Eroded joints in the rest of the masonry should be raked and
repointed. Where natural gas is burned, dampness due to condensation
is not unusual and a drain may be needed. Where such conditions exist,
advice should be sought from the manufacturers of the equipment as to the
proper remedy.
A chimney that becomes too hot to permit holding the hand against
it should be carefully inspected by a reliable mason and adequately
protected as suggested in the preceding pages.
If, after a chimney is cleaned, an examination discloses holes, unfilled
joints, or other unsound conditions out of reach for repair, it is
advisable to tear the masonry down and rebuild properly. Inside bricks
that are impregnated with creosote and soot should not be used in the
new work because they will stain plaster whenever dampness occurs. It
is almost impossible to remove creosote and soot stains on plaster and
wallpaper. Sometimes painting the plaster with aluminum-flake paint or
waterproof varnish hides the stains.
A hatchway cut through a roof is convenient when high chimneys are
repaired or cleaned, especially when access to the roof is difficult. The
hatchway should be located so that it will not be necessary to crawl over
the roof to reach the chimney and so that a ladder placed on the attic
floor will not be too steep for safe ascent. A watertight cover with
hooks to prevent its blowing off is essential. Such a hatchway is best
provided when the building is erected but can be readily built at any
time.