Building With Clay Brick
- Crusher sand, because of the shape of the particles (broken edges) yields a rather harsh concrete, but it is fairly consistent and contains no clay.
- River sand is generally clean and free from clay, the rounded particles pack together easily for good workability Pit sand contains excessive proportions of clay, but may be well graded otherwise. This is therefore not fit for concrete work.
- Beach or sea sand must be washed. Unwashed beach sand must not be used for mortars as its high cloride content will corrode steel reinforcement and cause excessive efflorescence.
- Dune sand is generally clean but poorly graded.
- Mine dump sand is generally unsuitable because it is too fine and may be contaminated with harmful chemicals.
Lime used in mortar is hydrated lime (commercial bedding lime) and not quicklime or agricultural lime. Lime give the best results when used with coarse sands. Lime with clayey sands can make the mortar over-cohesive and difficult to use. Lime should not be used with masonry cement.
A builder's wheelbarrow has a capacity of 65 litres
- For laying bricks and blocks in normal applications (SABS Class II)
- To lay 1000 bricks = 3 bags cement + 0.6 cu. m. sand
- 1 Bag of cement to 3 wheelbarrows of building sand
- For exterior and interior work
- To lay 100sq.m. (15mm thick) = 10 bags cement + 2 cu. m. sand
- 1 Bag of cement to 3 wheelbarrows of plaster sand
- 1 unit of mortar to 5 units of mortar sand.
- 1 unit of mortar to 5 units of plaster sand and stone.
- Plan site layout e.g. position of building, material stores, access etc.
- Store and protect all materials to minimise saturation and contamination.
- Control the wetting of bricks in hot, windy weather.
- Do not lay surface saturated bricks.
- Set out at ground level to locate all openings before commencing bricklaying.
- Lay out dry and minimise broken bonds.
- Prepare and take care of gauge rods - they are important quality control equipment.
- Work all levels from one datum.
As clay brickwork should be kept dry as possible during construction, cover the walls at the end of each day's work and during rain in order to keep brickwork free from mortar stains.
At the end of each working day clean the toe boards closest to the wall and turn the boards back to prevent rainfall from splashing mortar and dirt onto the brickwork.
- Mix small batches of mortar to suit building rate and 20 minute initial set timing.
- Bed all DPC's on fresh mortar
- Blend face bricks from a number of packs to minimise colour bonding.
- Plumb, level and square brickwork
- Fill all mortar joints solidly to minimise water penetration.
- Clean mortar dropping from cavities regularly
- Pay attention to DPC details Incline brick ties downwards to the outer leaf.
Stretcher bond (alternate layers of stretchers)
English bond (alternate layers of stretcher and header courses)
Flemish bond (alternate stretchers and headers in the same course)
English Cross or Dutch Bond. English cross or Dutch bond is a variation of English bond which differs only in that vertical joints between the stretchers in alternate courses do not align vertically. These joints center on the stretchers themselves in the courses above and below.
There are two methods used in starting the corners in Flemish and English bonds. Figure 3 shows the so-called "Dutch corner" in which a three-quarter brick closure is used, and the English corner in which a 2-in. or quarter brick closure, called a "queen closure", is used. The 2-in. closure should always be placed 4 in. in from the corner, never at the corner.
Clay bricks purchased from non-accredited sources could have unacceptably high porosity and water absorption rates and might need to be soaked on site with water before being used. This slows down the rate of water from the mortar being absorbed by the brick and hence enable a better and stronger bond between the brick and the mortar.
The trench sides must be straight and plumb and the bottom of the trench level, except in exceptional circumstances.
To ensure that the foundation is level and of uniform thickness, level pegs are to be placed in the trenches to indicate the concrete thickness. These levels are veryÂ Â important as they represent the start of the brickwork.
When the ground slopes, the trench bottoms must be stepped so that the foundation itself does not slope but is stepped. The step should be equal to one or more courses of brickwork.
Top level must be to at least 150mm, or two brick courses about external ground level.
The use of masonry reinforcement is a very simple and cost-effective way of greatly enhancing the strength and durability of masonry construction by providing both structural and crack control benefits.
It ties the wall together thus providing stability. Over unsupported openings like windows ,doors etc., Brickforce strengthens the wall. If you are building on unstable ground (i.e. there is movement in the ground) it is always good practice to use brick force thus ensuring a very stable wall.
Various types of alternative masonry reinforcement products are also available including mesh and wire.
I suggest a double skin masonry wall in standard imperial clay brick, with each leaf 106 mm in thickness. This will yield an overall wall thickness (unplastered) of 212 mm which will have a nominal fire rating of 240 minutes.
I would recommend supporting each 4 meter length of wall with a 340 x340mm brick pillar at each end, as well as using wire ties as suggested.
Chris Dickinson Corobrik
Will expansion set up compressive stresses if the gap is insufficient?
Answer The gaps on the pavers are 2mm to 6mm, which are to account for both PA and PB pavers so that lines may be maintained. (see the tolerances in the spec's on both types of pavers)
The "nibs" technically are only to assist with laying and are not for any structural reason. Most nibs are offset so as not to end up contacting each other, but strictly speaking, the jointing material is designed to diffuse the lateral and vertical forces by transferring them through to the bedding sand and sub-bases layers.
It is highly recommended that the grade of jointing material is different to the bedding sand, to expand in the joints and create the lockup. It must also be vibrated so that it fills the joint to the bottom and in so doing allow the forces to be transferred through. Again, one of the more important issues in the design is the edge restraint which holds the whole system together, and patterns relevant to the usage are also critical.
Please download the "Movement of Brickwork" technical paper.
Dave Bass BuildSafe South Africa
Thermal insulation or thermal resistance is achieved by means of three different mechanisms of attenuation of heat transfer: these define the three types of thermal insulation: resistive, reflective and capacitive, two of which are commonly present in insulated masonry wall assemblies. The third, reflective insulation, is often used in low mass (timber or light steel frame) walling constructions
A braai will never reach these kinds of heat and all facebricks are fired to around 1000 – 1250'C. The heat in the fireplace must get higher than this to have any effect on the brick. Generally your mortar joint will fail before the brick. What I always suggest to people is the following.
Build the outer skin of the sides of the braai/fireplace with a standard mortar mix (1 bag cement : 3 Barrows Sand) with brickforce and cavity ties. Build the inner skin with a well burnt clay face brick using a weaker mix (1 bag : 6 Barrows Sand) – this allows more joint movement and reduces cracking from heating.
The base is normally the area that gets the most heat as the fire is resting on this. It is also normally made from concrete (cast or lintels) which cannot withstand these high temperatures. Here a clay paver or solid clay brick can be laid on a sand bed. Do not cement bed or grout – it must have some movement to allow for heating and cooling expansion / contraction. The bricks / pavers at the opening to the braai can be grouted in to form an edge restraint. The fire generally is never built right at the opening so they don't get as much heat. Grouting these prevents the pavers behind from falling out / working loose. It acts like a kerbing.
Mark Hunter-Smith Algoa Brick
The bonding pattern/layout of bricks around windows Please see attachment 1 for various options available.
The installation of lintels - 280 mm cavity wall) As per the drawing on attachment 2: You would need to use two lintels, one 106mm and the other 164mm as illustrated.
Installation and waterproofing of window sills Attachment 2 shows for various options
Closing, sealing and rain-proofing the tops of parapet walls. Two methods are shown on attachment 1 but I would suggest you discuss this with a waterproofing or roof specialist before implementing.
Recommended : wall-tie spacing
We recommend at least 3 wall ties per sqm of walling. I'm not sure which region of SA you reside in but in Cape Town these are readily available at nearly every building material supplier.
I need to stress that the drawings attached are only typical details and each projects detail need to designed around that specific applications. Therefore, I would strongly recommend that it be discussed with a qualified architect or engineer to see if they are best suited for your particular application.
All the best to you with this project.
The attachment are from "Building Construction and Graphic Standards" written by Andre Grobbelaar. For a more detailed referencing herewith the books details:
ISBN-13: 9780620077873 (ISBN-10: 0620077875)
Publisher: Anglo-Rand Publications
Publication Date: 01 Dec 2006
Country of publication: South Africa