Building? How to KNOW your home’s corners are 90 degrees
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.
Clear all the rubble and have it removed from the stand. This is to prevent the contractor from possibly using it as filling. The top 200mm of the top soil must be removed and stock piled on site. You could use this to level your garden or to create terraces.
Clearly mark all the trees which should NOT be removed to prevent misunderstandings.
Albert says: “Remember you are not allowed to change the natural ground level of the stand by more than 1m without permission from the town council”
Special attention should be paid if a tree is removed from where the house will be constructed. Make sure the stump and all the roots are removed before the hole is filled and compacted. Inform the engineer where a tree was removed in case he needs to install extra reinforcing material into the foundations.
Large trees dry out the soil because they absorb a lot of water and their removal will change the moisture content of the soil. This change in the moisture content will affect the settlement of the foundation.
It is not advisable to build the house close to an existing large tree, or to plant a young tree which will grow tall near the foundation. Consult the engineer or horticulturist who will give you a ruling on which trees one should not plant.
Check for termite activities. It is recommended that the plinth and foundations be treated with poison spray before the concrete of the surface bed is poured. The pest control company should at least give you a five-year guarantee.
From the start, accuracy is of the utmost importance. Use the “3, 4, 5 formula” to calculate that the corners of the house are 90° as this cannot be checked with a square.
This is a mathematical formula. When the length of A is 3m and B is 4m and C is 5m then the corner will be 90°.
This is how you use it on site:
- Put in a peg on a corner
- Measure 3m in the direction of A
- Measure 4m in the direction of B
- Measure C now and if it is not 5m, then the corner is not 90°, adjust the direction of A or B until it does measure 5m, then you have a 90° corner
The other figures (1.5, 2, 2.5 or 1.75, 1, 1.25) can be used when you have smaller rooms, to ensure they have 90° corners.
Check the sizes on the plan and make sure that they balance by doing it the following way: Add up the internal sizes of the rooms and the walls to check if they balance with the overall dimensions. Some plans have many unnecessary dimensions which can confuse you, as well as the contractor. Check the overall dimensions (outside to outside) of the building after the bricklayer has set it out to ensure that the overall size of the building is not smaller than what is shown on the plan.
Make sure where the building lines of the stand are. This is the distance which the building must be away from the street and the adjoining stands. String lines along the building lines, thus ensuring that no costly mistakes will occur.
Make very sure that the building is square and all measurements are as per plan. Check and re-check it again. The motto of a carpenter is: Measure twice and cut once.
Install additional pegs at strategic places when setting out, in case some get lost and it has to be redone.
The sides and bottoms of the trenches must be level, plumb and straight.
Steps must be provided in the trenches when the site is on a slope. The sizes of the steps must be in multiples of 85mm to make the building of the plinth easier
Next time: Is your foundation right for your home?