1. GENERAL NOTIONS AND CLASSIFICATIONS

Definition :

• A wall is a continuous, usually vertical, solidstructure of brick, stone, timber or metal, whichencloses and protects a building or serves todivide buildings into compartments or rooms.

• They carry and transmit to the foundations theimposed vertical loads from other buildingelements (beams, floors, and roofs) and ensurethe stiffness of the whole structure. They alsoprotect the structure from the horizontal actionsof wind and earthquake, acting as wind bracing.

• Walls are defined as external or internal todifferentiate functional requirements, andalso as load bearing or non-load bearingto differentiate structural requirements.

− load bearing walls, those that carry imposedloads, such as those transmitted by floors,roofs…;

− non-load bearing walls which can carry justtheir own weight and if they are made ofmasonry are termed panel walls;

− non-load bearing walls supported by otherstructural elements, those related to a framedstructure

− load bearing walls, those that carry imposed loads,

− non-load bearing walls which can carry just their own weight

(made of masonry are termed panel walls);

− non-load bearing walls supported by other structural elements,

related to a framed structure

Construction types of walls: a.- monolithic,

b.- masonry, c.- frame, d.- membrane.

Functional requirements

• The function of a wall is to enclose and protect a building or to divide space within the building. The main functional requirements are:

1) Stability

2) Strength

3) Durability

4) Weather resistance

5) Fire resistance

6) Thermal insulation

7) Sound insulation

• Stability Together with floors and foundations, walls must ensure

the stability of the whole building. The stability of the walls may be

affected by foundation movement, eccentric loads, lateral forces

(wind, earthquake) and expansion due to the temperature and

moisture changes.

• Strength The walls should be designed to safely support their own

weight, wind loads, the loads imposed by floors and roofs and other

loads which may emerge during the life service of the building.

• Durability A block wall should be durable for the anticipated life of

the building and require little of any maintenance and repair.

• Weather resistance The external walls must be designed to provide

adequate resistance to rain and wind infiltration. The behaviour of a

wall in excluding wind and rain will depend on the nature of the

materials used in the construction of the wall and how they are put

together to create a unitary façade without discontinuities.

• Fire resistance The resistance of the elements of a structure tocollapse, flame protection and heat transmission during a fire isexpressed in periods of 2 to 6 hours in order to allow sufficienttime for the safe escape of occupants during fire.

• Thermal insulation To maintain reasonable and economicalconditions of thermal comfort in buildings, walls should provideadequate insulation against excessive loss or gain of heat, haveadequate thermal storage capacity and the internal face of wallsshould be at a reasonable temperature. For insulation, lightweightmaterials with low conductivity are more effective than densematerials with high conductivity whereas dense materials havebetter thermal storage capacity.

• Sound insulation Sound is transmitted as airborne sound andimpact sound. The external (envelope) walls are exposed directly tothe airborne sound of the streets and they must insulate the internalspace from this noise. Usually the opaque parts of the walls hasenough thickness and mass per square unit to confer goodacoustical insulation qualities.

• Natural lightening The natural lightening of buildingrooms is made through the glassed surfaces of the(building envelope) windows or doors. The objective ofthese spaces is to provide adequate visibility accordingto the functional destination of the room and also acomfortable visual communication with outdoor space.

The main aspects of this functional requirement are:

to provide a adequate level of light in any place of the room;

to supply a uniform natural light in the whole room avoiding the too shiny surfaces or those surfaces with too much shadow;

to provide, as much as possible, natural daylight all over the year.

Generally in the practice of building design and construction it isrespected a proportion between the surface of the room floor andthe glassed surface from the external wall of the room. Theexpression of this ratio is:

Sw mSf

2. CONSTRUCTION OF WALLS

2.1 Clay soil wallsThe non-fired clay ground can be used for walls in the following ways:

• as a monolithic wall, when the clay is treaded in fixed or sliding shuttering;

• as non-fired bricks, shaped and pressed by hand in regular wood moulds, and bonded using a mortar of clay and lime. The blocks are dried by sun ;

• pressed between two "sheets" walls of wattle or sleets.

Because the clay is sensitive to moisture variation and dose not resistto the water, its properties can be improved using some additionalmaterials as sand, cement or lime and fibrous materials such as

straws or tow.

• - roofs with wide eaves ( 50 cm );

• - the walls will be placed on high concrete or stone bases and will be insulates with horizontal waterproof membrane ;

• - the walls will be rendered with a lime and clay mortar.

2.2 Stonework

• Natural stone is durable but expensive and

it is, therefore, used today mainly as a

facing material, predominantly as a

relatively thin veneer fixed to a solid

background of other material. River blocks

or quarry stones are used.

• Mixed masonry wall :

a. concrete & stone

blocks, b. brick &

stone blocks masonry

Rubbed walls• These are built as random rubble walling using the

stones of random size and shape as they come from

the quarry, or as squared rubble walling using the

stone after they have been roughly squared.

Ashlar walls• Ashlar is the name given to the stones, usually over

300 mm and up to 450 mm in depth, dressed or sawn

to blocks of given dimension and carefully worked on

face and beds to produce fine joints not more than 3

mm thick

2.3 Brickwork walling

• Ordinary bricks (size: 240mm x 115 mm x 63 or88 mm) - clay is ground in mills, mixed with water( to make it plastic) and shaped and pressed byhand in a sanded wood mould. Then it is dried andfired at 900oC.

• Double pressed bricks (240 mm x 115 mm x 63) -are bricks made from selected clay, vary heavilymoulded and carefully burned so that the finishedbrick is vary solid and hard ( Rb is at least120daN/cm2 or 12 N/mm2 ).

• Considering the specific gravity there are C0, C1, C2, C3 and accordingly their strength there are mark 50, 75, 100, 125, 150. Bricks are used for internal or external loadbearing walls.

Bricks and blocks with vertical cells

Bricks with horizontal cells

• Mortar for brickwork - The basic requirementsof a mortar are that it hardens to such an extentthat it can carry the weight normally carried bybricks, without crushing, and that it is sufficientlyplastic, when applied to accommodate thevarying size of brick. The materials used formortars are sand, water, and lime or cement.The sand (which is reasonably cheap) providesthe strength; the water acts as a plasticizer andlime or cement provides the matrix. The ratio ofmortar is 0.190/0.230 m3 of mortar per 1 m3 ofbrick (worked) wall.

Bonding

• In building a wall of brick, it is usual to lay the

bricks in some regular pattern so that each brick

overlaps partly two or more bricks below itself.

The bricks are said to be bonded, meaning that

they bind together by being laid across each

other.

- English bond - Flemish bond

2.4 Blockwork - walls of building blocks

Lightweight

aggregate

concrete

blocks

• Bonding of blockwork - the principles of bonding arethe same as for brickworkbut because the range ofthicknesses available the blocks are only bondedlongitudinally as stretching bond and no cross bondingbeing required.

2.5 Walls of large prefabricated blocks

2.6 Walls of large precast panels

• The large panel is a rigid wall element made of reinforcedconcrete ( in combination or not with insulating materials ,lightweight concrete or terra-cotta products).

• The panels may be loadbearing, or non-loadbearing. According tothe position in the building, the panels can be used as external,internal, longitudinal or transversal walls.

Loadbearing panels for internal walls with a homogenous structure,made of reinforced concrete Bc20,÷Bc25, with 12...14 cm width forH=G+4F (ground plus 4 floors) and 16÷18 for H>G=4F

Loadbearing or non-loadbearing panels for external walls are of the following types :

• one layer of lightweight concrete ;

• sandwich panels, in three layers, two of reinforced concrete and thethird ( in between ) for thermal insulation ;

• panels of two layers, the first made of hard concrete grade Bc20 orbc25 ensure strength is made as a plate with caissons. The secondlayer for thermal insulation is made of lightweight concrete or otherthermal insulating materials;

• panels made of a reinforced concrete plate 5 cm thick, with ribs onedges and terra-cotta blocks forming a horizontal cell

The large precast panels joints

• These panels are ( usually ) precast and on each edgesteel bars or metallic plates are provided in order to bewelded to the next panel or floor reinforcement or platesin the connection region.

• Then after the joint region has been reinforced the spacebetween the precast panels is filled up with concrete.

2.7 Lightweight walls ( for framed buildings )

• The more logical use for a structural frame is insupport of some lightweight form of walling ofsufficient strength to be self-supportingbetween frame members and with adequateresistance to the penetration of rain and windand adequate thermal and sound insulation.

• The main materials used for lightweight walls aretimber (boards, planks, collars, strips, plywood,chipboards) metal sheet (of aluminium, stainlesssteel), thermal insulating materials (expandedpolystyrene, mineral wool, glass wool).

Cladding walls1. Solid

brick or

masonry

walls ,

2. In-fill

panels

Curtain walls

• Curtain walling is the name given to thesystem of buildings cladding with thinsheets of glass, metal or other impermeablematerials, that fulfil both function of walland window, supported by slender metal ortimber frames or grids attached to the faceof structural frame, in form of curtain wallsystem.

AUXILIARY ELEMENTS FOR WALLS

1. Wall bases - The bottom of the external wall near the ground surface is

named the base. The base must support accidental shocks and

environmental actions more than other parts of the wall. The base of the

wall is usually 50...60 cm high from ground level.

2. Cornice - A decorative moulding

at different levels of the walls

(usually at the top), plain or

with enrichments. External

cornice directs raindrops away

from the outside of the wall and

helps protect the roof against

fire from below.

3. Continuous belt straps or wall beams - Belt straps (or wall

beams) are building elements placed in the wall under the floor plates

or on the top of the foundations, in order to join together the floors and

the walls and to support the tensile stresses which are generated in

the walls.

OPENING IN BRICK & BLOCK WALLS

The openings for windows and doors may have in elevation rectangularshape or a curved one, especially at the top of the opening.