In the pueblo system of construction roofs and floors are the same; in
other words, the roof of one room is the floor of the room above, and
where a room or house is but one story high no change in the method of
construction is made. The erection of walls was only a question of time,
as the unit of the masonry is small; but the construction of a roof was
a much harder task, as the beams were necessarily brought from a
distance, sometimes a very long distance. The Tusayan claim that some of
the timbers used in the construction of the mission buildings, which
were established prior to the insurrection of 1680, were brought on the
backs of men from San Francisco mountains, a distance of over 100 miles,
and references to the transportation of timber over long distances are
not uncommon in Pueblo traditions. In De Chelly great difficulty must
have been experienced in procuring an adequate supply, as in that
portion of the canyon where most of the ruins occur no suitable trees
grow. Doubtless in many cases, where the location, under overhanging
cliffs permitted, roofs were dispensed with, but this alone would not
account for the dearth of timber found in the ruins. If we suppose the
canyon to have been the scene of a number of occupancies instead of one,
the absence of timber work, as well as the much obliterated appearance
of some of the ruins, would be explained, for the material would be used
more than once, perhaps several times. The Navaho would not use the
timber in cliff ruins under any circumstances, and they would rather
starve than eat food cooked with it. Many of the cliff outlooks, being
occupied only during the farming season and being also fairly well
sheltered, were probably roofless.
Timber was used as an aid to masonry construction in two ways--as a
foundation and as a tie. Many instances can be seen where the walls rest
on beams, running, not with them, but across them. These beams were
placed directly on the rock, and the front walls rested partly on their
ends and partly on the rock itself. Plate LII shows the end of one of
these beams. In nine cases out of ten the beams do not appear to have
served any useful end, but perhaps if the walls were removed down to the
foundations the purpose would be clear. Sometimes a beam was placed on
the rock in the line of the wall above it. The single or separate room
occupying the western end of the upper cave in the Casa Blanca ruin is
an example of this use. The front wall rests on beams, as shown in plate
XLVI. Some of the back adobe walls in the eastern part of the upper ruin
rest on timbers, and instances of this feature are not uncommon in other
parts of the canyon. The southeastern corner of the tower in Mummy Cave
ruin in Del Muerto rested on timbers apparently laid over a small cavity
or hole in the rock. The timber was not strong enough to support the
weight placed upon it, and consequently gave way, letting the corner of
the tower fall out.
Cross walls were sometimes tied to front or back walls by timbers built
into them, but this method, of which fine examples can be seen in the
Chaco ruins, was but slightly practiced here. Timber was used also to
prevent the slipping of walls on sloping sites, being placed vertically
and built into the masonry; but as this use is a constructive expedient
it is discussed under that head.