Building? Here’s why your double-door garage lintel is sagging
There is no user manual for all aspects of homeownership, from moving, to taking occupation and to maintaining and understanding common and uncommon defects. Albert van Wyk has more than 38 years’ worth of building experience and has put all he has learned into a concise, easy-to-use reference book entitled, The Proud Home Owner. He has granted HomeTimes exclusive access to republish portions of his book to help homeowners make better decisions around buying and selling, as well as maintaining their properties.
This is the main structure above the plinth. I will assume that an experienced bricklayer is doing the work, and that you only have to watch out for mistakes. You must now be alert because he will test your knowledge and might want to take short cuts. I suggest that the English garden wall design is used in all 220mm wide walls. Five courses are laid in stretcher bond and the sixth one is a header course.
The bricklayer must now set out the building on top of the surface bed. This must NOT be done in stages but the entire floor must be done in one session to prevent mistakes. All the rooms can now be checked that they are the correct sizes and that they are square.
The mortar (dagha) mix is important. Do not ask the bricklayer what the mix is, ask the labourers who are doing the mixing because it is here where you will get the truth.
If you cannot remember what the mix should be, look on the back of the cement bag. Remember two bags of cement is one wheelbarrow by volume.
Clay bricks must be wet or damp when they are laid, but not cement bricks. Do not mix clay and cement bricks in the same wall.
Take care where internal walls are joined with outside walls, they should tie in. This is a typical short-cut which the bricklayer might take. Cracks can develop in the corners if the walls are not tied in (bonded).
This is a 220mm-thick brick wall between the house and the garage and must extend to the underside of the roof cover. The wall will prevent a fire in the garage from spreading into the house.
An engineer must design the basement but you must take the following into consideration before you decide to have it done.
- How much the underground water table could increase during a heavy rainy season?
- Will you be able to control or divert the stormwater from your stand and from the neighbour’s, away from the basement area?
It is recommended that a drain system be installed at the bottom of the basement as a precaution for draining or pumping water away. Pay special attention to the waterproofing instructions because that is critical for every basement.
Albert says: “I think this is a very important part of the construction process”
Pre-stressed, precast concrete lintels are used particularly over openings. A pre-stressed lintel is made by casting concrete around high tensile, stretched wires which are anchored to the concrete so that the concrete is compressed by the stress in the wires.
It will be to your advantage to discuss this aspect beforehand with the contractor so he can order the correct lintels. Do not wait until he has made a mistake because it will be difficult to rectify the mistake once a lintel is installed incorrectly.
The distance by which the lintel is supported by the brick work on both sides is important.
Install 1.5m lintels and not 1.2m over all standard door frames (900mm wide.)
I recommend that the following lengths be installed over these openings, which are longer than normally specified.
Lintels are available in standard lengths with 300mm increments.
Pay special attention to the lintels over a double-garage door opening. I recommend that a “concrete plank” is used over a double-door garage opening, or any opening larger than 4m. A concrete plank is like two lintels which are cast together. These lintels (planks) are extra strong and will not sag.
Lintels must be imbedded level in mortar on the bricks and all perpends and joints should be properly filled.
A minimum of five brick courses must be built on top of the lintel to form a structural beam which will be strong enough to support the roof or the first-floor slab.
Watch out for excessive dagha over bricks in the corners. The bricklayer may have filled the gap in order for you not to see that the bond is wrong.
Excessive dagha (mortar) over the ends of the lintels is also an indication that the lintels are too short.
Cavity walls are walls that consist of two parallel rows of bricks, tied to each other with wall ties to form a cavity of at least 50mm between the leaves.
External walls of buildings in areas exposed to prolonged heavy, wind-driven rains should be constructed with a cavity. The purpose of the cavity is to prevent water reaching the inside walls of the house.
Weep holes must be formed in the outer leave, above the DPC by leaving those perpend joints open. As the work proceeds, this cavity should be kept clean and free of mortar.
It is not required that these be installed any more, but it can serve a good purpose to improve ventilation in a bathroom.
Black spots (mould) could develop on the ceiling of a poorly ventilated bathroom. This is caused by the condensation of steam on the ceiling.
The windows should be kept open or an extractor fan or airbricks can be installed to improve the ventilation. Also see the chapter on maintenance for more detail regarding this aspect.
The use of 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 walls together, thus providing stability. Install brick force in every course above all lintels. Above openings like windows, doors etc., brick force strengthens the wall. If you are building on unstable ground (i.e. where there is movement in the ground) it is always good practice to use brick force, thus ensuring a very stable wall.
The positions where the brick force should be installed in the walls will be indicated on the plan, or it will be an instruction from the engineer.
Brick force is available in rolls, but is not always straightened and flat when it is installed and is therefore not as effective as it is supposed to be.
Next time: Learn how many bags of cement and quantities of river sand and stone are needed to make 1m³ of medium-strength concrete