This is a 100mm cavity block. It can only be laid on its edge. The 100mm cavity block is lighter than the solid block but has better resistance to the weather. It can only be used above ground level.
This is a filler block (stock brick). It’s main uses are for making up levels in block walls e.g. around window and door openings.
This is a 215mm hollow block. There are 9.88 blocks per m2. These blocks are only used above ground level, mainly to build houses, sheds and boundary walls. In practice hollow blocks are difficult to cut therefore there are purpose made half hollows commonly as “footballs”.
Jointing
Because Fairfaced blocks are not to be plastered jointing must be of a good standard. The following joint finishes can be used on Fairfaced blocks.
Lintels
Lintels must be propped at 1.2m intervals until masonry has matured (dried).They should be bedded in mortar at supports. Lintels should have the following minimum bearing on each side.
150mm for spans up to 1.5m
200mm for spans 1.5m to 3m
Damp Proof Course (DPC)
The Building Regulations state:
The floors, walls & roof of a building shall be so designed and constructed as to prevent the passage of moisture to the inside of the building or damage to the fabric of the building
All walls should:
- Prevent moisture from the ground from reaching the inside of the building.
-
Not be damaged by moisture from the ground
- Not carry moisture from the ground to any part of the building that could be damaged by it.
- Resist the penetration of rain or snow to the inside of the building
- Not be damaged by rain or snow
Cills
Window cills should be enveloped in dpc. A dpc of suitable width should be used e.g. 450mmWindow cills should be 100mm longer than the opening on each side, e.g. a 1.800m window opening requires a 2.000m cill.
Mortar
Mortar quality is an important consideration in the design and construction of brickwork and blockwork.Mortar is made of aggregate (sand), binder (mixture of lime & cement) and water. The lime can be replaced by the use of plasticiser. A good mortar should cling to the trowel and not stiffen too quickly. The basic rule for mortar is cement provides the strength; lime or plasticisers improve the workability.
Types of Mortar
- Ready to use mortar (trowel ready).
This type of mortar is delivered on site ready to use. Setting time on this mortar varies, 36 hour on weekdays and 72 hour for weekends. The manufacturers instructions should be followed carefully.
How much mortar
When the type of mix to be used has been decided the volumes of materials required can be calculated. One tonne of building sand when mixed with cement & lime will provide enough mortar to lay 250 solid blocks on edge or 125 blocks on flat.
1m3 of trowel ready mortar will lay 1000 blocks on edge and 500 on flat.
Curved Brickwork
The 3 most common ways of constructing curved work are as follows:
- Alignment with templates.
- Trammel & Plumbing.
- Leader bricks, levelling & plumbing.
Alignment with templates
A curved wall can be constructed using a template as shown, made from timber and cut to the required curvature of the wall
Trammel&Plumbing
To set out curved walling, you must have the following information:
The exact location on site for the curved wall.
The striking point (the point from where the circle or curve is taken from)
The radius of the curve (half the diameter)
Once this has been found the wall can be marked out on the foundations as shown below.
Water feature built using the trammel & plumbing method.
First-course
Carefully bed the first course of bricks to the line of the radius marked in the screed.
Use the trammel to check the alignment. Any “kinks” in the first course will continue up the full height of the wall.
Level in the bricks using a level and straight edge.
Plumbing points and templates
As there are no quoins either end of a curved wall, establish plumbing points at about 1200mm intervals. (Make templates approximately 1200mm long to work alongside this)
Like quoins in straight walls plumbing points control plumb, gauge and level for the full height of the wall, so great care should be taken when plumbing a curved wall.
Straight-bricks-and-templates
The whole length of the face of straight bricks cannot follow a curved template. Therefore the following procedure is used
- For a convex (outward) face both arises of all bricks must touch the template.
- For a concave (inward) face where a reverse template is used the centre of the brick must touch the template with both arises the same distance from the template.
Leader bricks leveling and plumbing
After the curve has been set out using either the trammel or template the curved wall can be constructed using just a level, straight edge and leader bricks.
A leader brick is one which is plumbed, levelled and gauged at several points along the curve. The bricks of the curve are built between these leader bricks as shown below.
KEY POINTS WHEN CONSTRUCTING CURVED WALLING
- Locate exact position of striking point
- Accurately shape templates to correct radius
- Set out carefully, keeping trammel horizontal
- Lay out bricks dry around the curve to check the size of cross joints
- Make distances between plumbing points equal to length of template
- Plumb down from datum's to begin gauging at each plumbing point
- Continually check plumb and gauge, only at plumbing points
- Pencil plumb perpends at every plumbing points
- Level bricks between plumbing points with great care.
REINFORCED BRICKWORK
The designers of modern buildings are constantly using new techniques, methods and materials to provide structures with increased strength and reduction in loading. Because of this trend the use of reinforcement in walling is becoming a common practice.
The reinforcement of brick walls allows for a reduction in wall thickness. When walls are reinforced above openings the compressive strength is increased because the brickwork acts as a beam.
Types of Reinforcement
- Exmet expanded metal mesh
- BRC Brickforce
- BRC Wallforce
- BRC Bricktor
- Rod Reinforcement
Exmet Expanded Metal Mesh
This is a Diamond-shaped mesh. It should be enveloped within mortar bed. It is used to resist both horizontal and vertical pressure.
B.R.C. BRICKFORCE:
This is a Welded product consisting of two parallel wires joined by cross wires every 304mm. While it is used to resist horizontal pressure it also adds considerable compressive and tensile strength.
B.R.C. WALLFORCE:
Looks like brickforce but is used for cavity walls.4 main wires run parallel along the length joined by welded cross wires with a drip (which take the place of conventional wall ties) @ 450mm centres.
B.R.C BRICKTOR Stainless steel or galvanised wire mesh used for reinforcing over openings, bonding and strengthening corners and intersections.
ROD REINFORCEMENT
12-20mm Diameter bars are used tied together with 3mm tying wire. It is used vertically to resist lateral stresses and reduce wall thickness.
Types of bond used to accommodate vertical rod reinforcement:
Quetta Bond
Rat-trap Bond
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Perforated Bricks
Thick hollow walls with concrete and rod infill.
Retaining Walls
The major function of any retaining wall is to act as an earth retaining structure for the whole or part of its height on one face. The other face is exposed to the elements.
- Small height retaining walls are up to 1m high.
- Medium height retaining walls are from 1m – 6m high.
Small Height Retaining Walls
Most small height retaining walls are built of brickwork or a combination of brickwork facing and blockwork or mass concrete backing.An adequate drainage system in the form of weep holes or subsoil drainage behind the wall should be used to reduce hydrostatic pressure on the wall from water. Weep holes consist of uPVC pipe built into the wall to allow water from the soil to drain through the wall into a channel.
They are positioned at 2.000m centres and 75mm above the channel
Brick Retaining Wall
Small height retaining walls must be stable. The usual rule of thumb is for the height to lie between 2 & 4 times the thickness of the wall.
Choice of Brick
Due to exposure to severe weather conditions careful consideration should be given to the type of brick used in building a retaining wall. A brick that is fully frost resistant and with a low salt content such as an engineering brick should be used.
Mortar
The mortar mix used is also an important consideration. Sulphate-resisting Portland cement should be used instead of the ordinary Portland cement.
Sinead Carr
C06354548
DT491/1
Brickwork
Attention of: Michael Griffin
