Basic guidelines to owner home building
Many South Africans are choosing to build their own homes instead of buying an existing property. Reasons for this vary but mostly for the cost saving (It is said that a saving of 25% can be made on the capital outlay of the proposed project when building yourself as oppose to buying), other reasons might include the great challenge of taking on a building project or the fact that it can create a great sense of self-achievement.
For a number of reasons the cost of building went up tremendously in the last couple of years. In 1998 an average house with regular finishes could be build for appx. R1800/sqm whereas at the time of writing this document (2006) the rate of building the same house would be around (R3500/sqm) This probably had a huge influence on the "property boom" as perceived by South Africans in the recent years.
With the above in mind, it goes without saying that it is essential to hire a good contractor (for a list of good contractors in your area, contact the NHBRC or National home builders registration council) Also know that getting a building loan from a respectable financial institution would require you to hire a contractor who is registered with the NHBRC, a loan would not be granted otherwise)
The experience, skill, efficiency, and contacts of a seasoned professional contractor can yield dividends for years.
CHOOSING A SUITABLE STAND
Try to avoid irregular shaped plots, if possible a square or rectangular shaped plot lends itself to easier planning. Optimum shape are more or less a 4:3 ratio. If considering a pan-handle, know that the pan-handle makes up a lot of the size of the total area of the plot and that this is generally un-usable and would cost generally more to pave that a regular plot.
Generally flat sites are easiest to build on, but one might choose a sloped site as it often is accompanied by great views, but keep in mind that sloping sites, no matter how steep will often call for professional help in the planning stages.
If you are planning to possibly extend the house in future make sure the site lends itself towards making this possible sensibly. It would often not make sense to extend if there is only open space on the western or cold southern side of the plot.
North facing plots are the best in the Southern hemisphere as they get more sun, especially in the winter months when the sun is lower. Views or other advantages will influence a buyer to buy alternatively orientated sites, but never consider buying a western orientated site. You will seriously regret it afterwards.
Do a proper soil investigation before buying, or ask the developer/seller to provide you with a soil test. The cost of building on un-suitable soil is surprisingly higher with the need for special excavations & foundations.
Access to site
Mull over the possible accesses to the site, this often becomes a huge headache during building and even more so in many cases once you have moved in.
BUILDING THE SUPERSTRUCTURE
Make sure your builder has a proper store for the building materials delivered to site to prevent theft and also to protect the materials from weather, especially cement should be kept free from all moist at all cost. Bags of cement could be stored on a platform lifted on bricks etc.
Don't construct the storage hut too far from the road for easy delivery. Make sure that the proper sanitation facilities are provided as well and make arrangements to have the water connection activated.
This process involves the marking out of the building with lime powder, corner pegs and datum level references. Once the marking out is complete, make sure to double check that the proposed building does not cross building lines or servitudes.
If you are building on a sloped site the cut & fill excavations & filling will have to be done before hand.
Excavations & Foundations
Make sure that the excavations for the foundations are level and at least 550mm deep, most local authorities require the top of the foundation to de at least 340mm (4 brick courses) deep and see that the excavated trenches are free of water before concrete casting commences. For external walls the foundations are to be a minimum of 550mm wide for cement bricks and 600mm for clay bricks for a one storey building. The foundation depth to be around 230mm min. deep. These are for normal soil conditions. If you suspect that you have special conditions ex. Silt, Clay etc. consult your engineer as you may require a special raft foundation or even piles in cases where the top layer of extreme unusable quality.
When building on a sloping site, a stepped foundation may be required. Make sure that the top foundations ends overlap sufficiently (appx. 250mm) over the bottom strip for a normal strip foundation.
For unstable soils consult your engineer for a foundation design and have him do an inspection when the foundations are cast.
(Have a look at the details section for typical foundation details on the advice page of this site, you might also want to read the article on concrete construction in South Africa)
Waterproofing & floor slab casting
Residential ground floor slabs are usually only one brick course thick (Apprx. 75mm) and are layed on a well compacted crushed stone filling covered with riversand and on a adequate damp proof membrance (The dpm is often specified as a 250micron under surface bed layer). Make sure that the layer of riversand in sufficient in thickness and that it is well spread over the layer of crushed stone to prevent penetrations through the sheet. Also check that the final unfinished floor level is at least 2 brick cources (170mm) above the natural ground level to prevent stormwater or rising damp from entering the house and as required by local authorities.
See to it that the builder is keeping the floor slabs damp to ensure proper curing and that he has ordered his building sand and cement from sound suppliers who will supply him with the correct type of cement and aggregate mix for slab casting.
When the slab is cast check your plans once again to see that all conduits or pipes etc. are in place for the sanitary fittings (wc, whb, shr, sink, etc.) and for all the electrical fittings (plug outlets etc.)
Walls (Masonry work)
Before any bricks are laid check that the top of foundation is square and level once again.
Make sure you get good quality stock/face bricks from a sound supplier. When the bricks are delivered to site inspect them and see if more than 5 out of 100 are broken, if so the bricks might not be of optimum quality.
When using cement bricks/blocks make sure the bricks are dry before being laid as shrinkage might occur afterwards if they are laid wet which might result in mortar jointing getting loose. concrete based the supplier must supply a SABS certificate of compliance.
It is good practice to wet the bricks before laying them as the dust accumulated on them might act as a barrier between the mortar & the brick, also clay bricks might absorb a lot of moisture out of the mortar mix which it needs to cure (harden).
Before building of walls commences make sure that your builder installs a layer of 250micron Plastic sheet as wide as the wall as a damp proofing similar to the sheet below the floorslab. Where there are platform differences a vertical sheet should be installed to prevent damp to the lower levels.
When the building is in progress, see that the corner profiles (wooden masts with brick courses marked of at the corners of the house) are plumb and that brickwork is laid level as building proceeds. Make sure that the lines spanned between profiles are always level and stretched tight.
Bricks should be laid with brick-reinforcing every third to 4th course, and every course above door & window level.
Door & window frames should be built in and see that they are at the correct placement and height and that they are built in level. If you are building aluminium window frames, openings will be left and the openings will be measured on site and the windows built accordingly and installed just before plastering commences.
Make sure that lintels are resting at least 150 mm on both sides of openings for openings smaller than 1,5m, or 250 mm for openings wider than that.
Bricks must be laid plumb and level, with joints of about 10mm, properly filled.
With facebricks it is important that all joints are properly filled, otherwise water will leak through these joints into the interior skin of brickwork
Cavity walls (walls consisting of two brick skins with small gap - 40-50mm usually) needs to be build at all coastal residences with weep holes at the bottom for the moisture to escape. It is also good practice to build cavity walls at the western side of the building to eliminate the heat created on the walls by the scorching western afternoon sun.
Where cavity walls are built, wall ties are to be used between the skins, at a rate of 4 ties per square metre.
Roof design will depend on the type of covering and the span over which the structure is built.
A timber sub-structured roof typically rests on a wooden wallplate which acts as a "ringbeam" around the perimeter of the building to evenly distribute the loads to the supporting walls.
The trusses & wall plate is anchored to the walls with metal roof ties and needs to be built into the wall at least 4 brick courses from the top.
The roof trusses should be graded and treated and bear a mark of approval typically by the SABS. An engineering certificate of compliance should be supplied to you by the roof contractor.
The battens are the cross pieces of timber spaced as per roofing material used. For tiled roofs they are 38x38mm and spaced at appx. 330mm centres and 38x50 or 50x76 for sheetmetal coverings and spaced at 1,2 to 1,6m apart depending on the manufacturer.
Brandering are similar to battens but is nailed to the underside of the trusses for the ceiling to be fixed to it. They are typically 38x38mm in profile and spaced at 450mm centres. Make sure to have a trapdoor fitted in between at a suitable place. (See also trapdoor detail at the details page of this website)
Depending on the roofing type and manufacturer roof slopes may vary from 2 degrees to very steep angles. Typically tiled roofs will not have a smaller slope that about 17 degrees and will then require an undertile waterproofing membrane (this is typically done for roofs at a pitch greater than 45 or smaller than 26 degrees and also prevents dust from entering and act against wind loads that might be forced onto the roof)
Many sheetmetal profiles can be installed at a very small slope without difficulty.
Where ever there is a protrusion through the roof eg. A ventpipe, chimney shaft, parapet wall etc. these areas should be properly flashed with galvanized sheetmetal flashings.
Depending on the style of architecture or personal preference you might install a facia board and gutter or not; however if you decide not to, it is good practise and most local authorities will require you to build an apron of 900MM min around the house perimeter to prevent the falling water from corroding the earth around the house and cause rising damp or structural failure of the weakened brickwork by the moisture.
Construction of floors / Stairs
When constructing floors it can either be a wooden floor raised and rest of wooden floor joists (beams) and be concrete which is the preferred method because of its better insulating qualities.
For concrete ground floors see also the section regarding slab casting earlier. If you are building a wooden floor, especially at higher levels consult a qualified professional to work out the live loads which will act out on the floor.
When considering which flooring material to be used also consider the fact that a lot of services needs to run in the floor and will need to be covered from below is using wooden floor for the upper floors.
Local authorities usually require stair treads to be no less than 250mm and risers (vertical) to be no more than 200mm. These however are minimums and a comfortable stair should have at leas 270mm treads and 170mm risers. The 170mm risers also makes it easier if a concrete stair needs to be built into a wall module as 170mm equals 2 brick courses.
Other items and services
Plumbing & sewerage, electrical installation, landscaping, Special fittings etc. will not be covered in this document. Should you have any other questions please contact us and we will do our utmost to provide you with guidance.