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INTRODUCTION
– BASIC GUIDELINES TO
HOME
BUILDING IN SA
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 – 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
Shape
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.
Slope
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.
Size
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.
Orientation
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.
Soil
conditions
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
Storage
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.
Setting out
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 covering
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 – 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.
(For thatch roof
information refer to the article on thatch roof design on this website)
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 in
SA 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.
Compiled by JB, Architect & Founder of dreamhouses.co.za
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