STRUCTURAL DESIGN FOR ARCHITECTURE

loadbearing wall, the arch, the vault and the

dome). Another consequence of the method of

construction is that other materials can be

incorporated into masonry so as to augment

its properties. The placing of steel reinforce-

ment in the bedding planes to give masonry

flexural strength is an example of this.

Fire resistance

Masonry performs well in fire; it is non-
combustible and retains its structural proper-
ties at high temperatures.

Acoustic performance

Masonry walls form good acoustic barriers.

Thermal performance

Masonry walls provide a reasonable level of
thermal insulation. Their high thermal mass is
a further advantage which allows the creation
of enclosures with good levels of passive
environmental control.

5.2.2.3 Disadvantages

Lack of tensile strength

The lack of tensile and therefore of flexural
strength is masonry's principal structural
disadvantage and has restricted its use, in
modem times, to loadbearing-wall-type struc-
tures. The selection of masonry therefore
normally implies that the constraints of this
type of structure be accepted in the planning
of the building. The most obvious of these is
the requirement that a plan consisting of
parallel loadbearing walls be adopted and that,
in multi-storey buildings, the plan be more-or-
less the same at all levels.
The lack of tensile strength also makes diffi-
cult the construction of high-strength struc-
tural connections between masonry and other
structural elements. This has tended to restrict
the use of masonry in modern times to multi-
cellular buildings in which none of the interior
spaces is large.

Weight
In comparison to timber, masonry is relatively
heavy and while this has advantages (it is

responsible for the good performance of

masonry as an acoustic barrier) it also has

disadvantages. In particular, it results in high

dead loads being imposed on supporting

structures, such as foundations. It also affects

the cost of transport to the site.

Porosity

Most masonry is porous and while this may

not be a serious disadvantage so far as its use

as a structural material is concerned, it does

affect the structural design. In particular, where

the material is used for external walls, it

complicates the detailed design, which must

be such as to prevent water from penetrating

the building.

5.2.2.4 Conclusion

To sum up, the principal advantage of masonry

is that it possesses a good combination of

properties rather than that it performs

outstandingly well with respect to any particu-

lar criterion. Its good appearance and durabil-

ity, its reasonably high compressive strength,

its low cost, its thermal and acoustic proper-

ties and its performance in respect of fire make

it an ideal material for structural walls and this

is, of course, its principal use. In modem

practice masonry structures are usually based

on post-and-beam arrangements and the

particular properties of the material affect the

forms which are adopted. The general prin-

ciples which are followed in the planning of

masonry buildings, and which take these into

account, are outlined in Section 5.3.

The treatment of masonry which is given

here is confined almost entirely to the use of

brick and block manufactured components.

These are by far the most commonly used

constituents in the developed world, but

masonry is also constructed in a variety of

other materials such as natural stone and

mud. Although these materials are not dealt

with here specifically, the general principles of

loadbearing masonry which are outlined in this

chapter apply equally to construction in all

brittle building materials.

163

Masonry structures