Double Garage Cost Determinants and Functional Capacity
A detached double garage is a stand-alone garage (unattached to the house or any building) which can accommodate two cars. We are going to look at the cost of building of a 24 x 24 feet garage, which can be converted to 7.315 x 7.315 metres in metric units of measurements used in South Africa. These are the dimensions of the floor plan (gross floor area) measured corner-to-corner from the external side of the external brickwalls. Assuming that all other factors are constant and normal, the main factors affecting the cost of building any residential dwelling are the cost of Labour, Materials and Equipment.
Why Do You Need a 7.315×7.315m Double Garage?
The 3D garage sketch model illustrated in this post was drawn in real-life scaled dimensions. The car models are also scaled models. As you can see in the pictures, two big SUVs, the Lexus LX 2019 and the Mitsubishi Montero Sport 2016 can fit in nicely inside the garage while allowing room for an individual to move around and in between. There is even more room for smaller cars like the 2014 Volkswagen Golf GTI and BMW 318d F30. On all internal wall elevations, there is room enough to open a 813mm wide door in full swing, without touching or scratching the parked cars. You can if you want, paint or glue a door swing area sign on the floor to help you will accurate parking.
The estimated and actual construction cost during the course of building can be affected not only by the variations or changes in the cost of materials, but it’s also affected by site conditions such as type of terrain, sub-soil profile, water table, weather and other existing constraints such as building zone, location, site access, adjacent buildings, underground electrical conduits and site reticulation (underground water service pipes and drainage systems).
Depending on the stability of the construction index in your area, the price of materials is more likely to change within a shorter period than the cost of labour and equipment/plant. Labour rates tend to be constant and consistent over a long period in South Africa, until a time comes when government gazetted minimum wages are published and signed into law after a protracted period of collective bargaining with trade unions.
Hourly Labour Rates for Tradesmen and Labourers in the Building Industry in South Africa
According to a periodic report by CIDB (Construction Industry Development Board), an Employer survey carried out by the Bargaining Council in 2014 shows that 40% of Employers pay minimum wage workers at gazetted rates, 43% pay in-house rates, 3% pay Trade Union negotiated rates and 4% pay below the gazetted rates. Of course, this was an Employer survey, a Worker survey might reveal a different picture. This survey shows that wage rates are uniform throughout the industry.
According to the same report, the construction industry is the second-largest contributor of informal employment in South Africa, along with community and social services. It is the fifth largest contributor of employment in the formal sector. About 17% of informal workers and 8% of formal workers in South Africa are employed in the construction industry.
The labour cost of building a house will vary in view of the situation already stated above. Pay rates for informal workers are usually lower than that of formal workers. The informal sector is dominated by migrants who in most cases will have no choice but to accept rates below the minimum wage.
For the seven-year period 2012 up to 2019, hourly wage rates have increased by about 56.91% for unskilled labourers, and 75.49% for artisans. In 2012, the minimum hourly rates for Area A was R14.61 for general workers, R16.08 for class 4 builder’s worker and learner, R21,39 for class 1 builder’s worker and learner, R23.53 per hour for artisans (painter, carpet floor layer, water-proofer and crane operator), and a minimum of R25.88 per hour for artisans in other trades.
In 2019, the minimum hourly rates for Area A increased up to R21.20 per hour for labourers, R22.92 for general workers, R25.22 for class 4 builder’s worker and learner, R33.56 for class 1 builder’s worker and learner. Artisans (painters, carpet floor layers, water-proofers and crane operators) are now earning R36.92 per hour, and a minimum of R40.61 per hour for artisans in other trades.
Construction Index in South Africa 2008 to 2019
The construction input cost index in South Africa is a weighted composite value of material, labour, plant and fuel price indices. It measures changes in the price of materials, labour, plant and fuel over a given period. This building cost index is measured on a monthly, quarterly and annual basis. Changes in productive costs (labour, fuel, equipment, raw materials sourcing etc.) will affect the price of certain materials, which in turn will affect the cost of building. The construction material price index alone for building works was 96.7 and 104.1 in January 2017 and 2018 respectively. The figures for May 2018 and May 2019 were 104.3 and 109.8 respectively.
Effect of Terrain on Building Cost
Terrain is the gradient of land, the fluctuations and evenness with respect to the sea level. South Africa has a wide variety of geographical landscapes, from savannahs which are usually large expanses of flat grasslands, to semi-desert bushes, coastal lands and mountainous, hilly areas with valleys and steep slopes. Building on steep slopes will be much more costly than building on flat ground. In hilly areas with uneven land, the Foundations Bill of Quantities will be extra-ordinarily large, cut-and-fill bulk excavation will be required to get to reduced levels and fill up valleys with excavated material to create level formations. Foundation trenches and walls will be much deeper than on level ground.
Effect of Sub-soil Profile on Building Cost
The type of soil below the ground and the depth at which firm ground is found will determine the type of foundations you have to build. The most desirable soil type for a stable foundation is loam and rock. Loam is a mixture of various soils which don’t have the properties of loam alone. With stable and firm soils such as loam and soft rock, your foundations don’t have to go deeper than weak compressible soils such as sand, clay, peat, silt, gravel and soft chalk. These type of soils require deep foundations, for example when you are building close to the river bank, sea shore or valleys, you may need pile foundations or any kind of deep foundation that can reach the firm level. The deeper your foundations, the higher the cost.
Effect of Location on Building Cost
Your location will determine the construction costs in a way you didn’t imagine. That’s why the building cost per square metre in South Africa is not the same. It varies by province, city and location. How much you are expected to pay will vary depending on whether you live in a low income, middle income, upper middle income or high class area. If you outside the city outskirts, the cost of transporting building materials will be much higher depending on the distance. Demand is high and low in certain areas, if specific materials are unavailable in your region and they have to be sourced from a faraway place, this will increase the material price. What is the state of labour supply in your area? Are there shortages of skilled and unskilled labour? These are things that you have to consider. The minimum wage may not be enough to attract the much-needed labourers and tradesmen. How easy is it to access the site and are there adjacent buildings that may be affected by your project? Easy site access is good for delivery and coordination of teams and activities. Adjacent buildings, structures and services may need protection, some trees may need to be preserved. Safe passage ways for pedestrians may need to be erected. These costs have to be factored in your Bill for Preliminaries.
Preliminary Site Investigations
These include some of the aspects that were mentioned previously. Before you begin building on the site, you have to carry out a site investigation to determine the location of underground services such as water and electricity supply, including drainage systems. This prevents you from building on top of these systems or obstructing them. You cannot remove, tamper with or divert these services without authorization of the local municipality or building authorities. Doing so will attract a penalty and your application for building approval may be rejected. The assistance of the city council engineers/inspectors will be required in locating these services.
Cost of Building a Detached Garage made of Bricks in South Africa
Scope of Project: A detached double garage, size 24×24 feet (7.315×7.315m wide), gross floor area 53.51m2 (576 square foot), superstructure made of 230mm one-brickwall, rough tan facebricks, 2800mm high from plinth level (floor level), with 230x475mm high reinforced concrete beam (30MPa/19mm) over front entrance. The walls are unplastered both sides except for plinth, gables and RC beam over garage entrance. The plinth and gables shall be plastered with a Pebble Dash plaster finish, and painted with Firebrick colour finish. The RC beam shall be plastered both sides with a Pebble Dash plaster finish and painted with Burlywood colour finish. The floor consists of a 100mm thick reinforced concrete bed (25MPa/19mm), laid over DPM and hardcore filling, with a 35mm thick granolithic screed black top finish (grey colour). The substructure is made up of 300x700mm wide concrete footings (20MPa/19mm), foundation walls 700mm high made up of 230mm tumbled common bricks. Sloped concrete ramps will be required on the front entrance where the garage rollup door is positioned.
The roof structure is built from 10 timber trusses span 7315mm (24ft), riser 914mm high (3ft), top and bottom chords 51x102mm pine sections, inner members 51x70mm pine sections, all connected by 6mm thick steel gusset plates on both sides of the truss. Trusses to be held in place and stabilized against lateral wind forces by longitudinal bracing 100x30mm timber sections, and diagonal bracing 100x30mm timber sections. Purlins 75x50mm fixed longitudinally across trusses. Plasterboard ceiling fixed on 38x50mm sawn softwood brandering at 400mm centre to centre spacing. The roof covering selected for this garage shall be 0.7mm thick IBR box profile/ribbed Colorbond® steel sheets (Sky blue colour) 32mm deep and 1000mm wide units. The roof drainage system includes 90x90mm square galvanized steel gutters and 75x75mm square galvanized steel downpipes, painted with dark slate gray colour coating. Fascia boards and eaves soffit boards shall be installed to the side elevations. Barge boards and verge soffit boards will be fixed on gable ends. All painted with sky blue colour coating.
One pedestrian door 813x2032mm high will be placed on the right elevation. The vehicle entrance shall be fitted with a custom Wispeco garage door for opening 3025x2100mm high. Last but not least, the garage shall have a single medium-size casement window 763x783mm high with a side-hung half-width outside opening panel and fixed panel on the other side.
SUB-TOTAL: – R161,587.90
ADD: CONTINGENCIES – R3,200.00
TOTAL CONSTRUCTION COST: – R164,787.90
How To Build a 24×24 feet Detached Brickwall Garage
There are two options for building a garage. You can either go the DIY route if you already have building experience, skills and expertise. Will you have the time to build the garage by yourself and do you have the skills to set up all elements of the building such as the roof, ceilings, foundations, floor, walls, painting, rendering, electrical installation and automatic rollup doors? If you are skilled in one trade, it doesn’t mean you can do all trades, so you may still be required to hire and get the help of other tradesmen.
The best and most common option is to hire an experienced building contractor in your area. Not only will you have your garage built on time, but you will save yourself from making mistakes that may be costly in the long run. It’s a very risky business being a jack of all trades. Look for the right experts to do the work.
With that said, the first expert that you have to consult when planning to build a house or any accommodation is the Architect or Structural Engineer. They can design your building to comply with local building codes and they can easily get a building plan approval for you from the local municipality or building department.
Once your building plan gets approved, and city council inspectors have approved your site, you can start building. To make this post short, not longer than necessary, we shall only discuss the building method for the Substructure [Excavations, Foundations and Floor Structure].
If you want to see all the elements/parts of this garage structure, visit this link – Elements.
Clear the site on which you will be building. This is your residential plot or erven. Remove all grass, shrubs, bushes and all rubbish including grubbing up roots. Cut down unwanted trees and preserve the ones you want to remain. You cannot cut down trees outside your yard or plot, only those within the boundaries of your yard. Still, even if the tree is in your yard, you cannot cut down a tree if it is going to affect adjacent buildings, underground and overhead services. Get the approval of the local authorities.
Once you have cleared the site, strip the topsoil on the building area using a machine. The building area is the gross floor area occupied by the garage. The strip area shall include ramps and steps, therefore the total area that will be stripped is:
Floor – 7315 x 7315mm
Ramp – 7315 x 1000mm
Steps – 873 x 600mm
Scarify the ground or excavate to a suitable depth [220mm], the reduced level that will form the subgrade level. Cart away excavated material to a suitable spot on the site. Compact the ground to at least 95% Mod AASHTO density, breaking down oversized material and filling up holes with excavated material. Apply soil insecticide and weed killer on compacted surfaces.
Excavate Foundation Trenches:
From the strip level, you can start digging foundation trenches 700mm wide x 1000mm deep. Find out which is cheaper, excavation by hand using labourers or using wheel trenchers and other related machines. Cart away excavated material to a suitable spot on the site for storage. You are going to need this material for back-filling, so don’t move it to a dump site.
Compact the bottoms of trenches with a vibratory roller to the required 95% Mod AASHTO density, breaking down oversized material and filling up holes with excavated material.
On the bottoms, spread a layer of 50mm sand blinding or weak concrete [10 or 15MPa/19mm] if needed.
Apply soil insecticide to bottoms and sides of trenches.
Foundation Concrete Footings:
Excavations are complete, the next step is building concrete footings. Prepare unreinforced concrete 25MPa/19mm and pour the concrete inside the excavated trenches, forming a strip footing 700mm wide x 300mm thick. Tamp and vibrate the concrete to eliminate air bubbles. Allow the concrete to set and cure for at least 21 days.
When the concrete footings are dry and set, you can bring in bricklayers to start building the foundation walls. The foundation walls for this garage shall be 230mm thick one-brickwalls. Brick reinforcement will be laid every course. The plinth shall be plastered and painted. The walls shall be 800mm high up to the plinth level and 700mm high up to the natural ground level, so the plinth is 100mm high.
Back-Filling to Trenches:
Using material from excavations stored on the site, back fill the open spaces on the sides of foundation brickwalls. The external side shall be back-filled up to the natural ground level and the internal side shall be back-filled up to the strip level.
Earth filling under steps and ramps will be required. The contractor will take excavated material stored on site to create formations under steps and ramps. The filling is compacted to 95% Mod AASHTO density.
Imported Hardcore Filling:
After back-filling the trenches, the next step is filling the floor reduced level with imported filling. Start by filling the stripped levels with suitable hardcore material which usually comprises of gravel, crushed bricks, stones and other types of materials. This sub-base course (G5) imported material is spread on compacted sub-grade, levelled, stabilised to attain UCS>1.0MPa after 7 days and compacted in a single layer about 150mm thick to 100% Mod AASHTO density at OMC.
Imported Sand Filling:
A sand bed 50 to 75mm thick is spread and levelled over the hardcore filling. The purpose of the sand layer is to provide an even surface on which to lay DPM (Damp proof membrane) and wet concrete. It also prevents the hardcore material from puncturing the DPM.
Damp Proof Membrane:
Lay the DPM over the sand bed and allow for up-turned edges on vertical brick surfaces. One layer of 250 micron green polyethylene waterproof sheeting is usually installed.
Reinforced Concrete Slab:
Surface beds comprising of 30MPa/19mm concrete are poured on polyethylene waterproofing. The ground floor slab for this garage shall be 100mm thick. Pour in bottom concrete cover about 45mm thick, then lay some fabric steel reinforcement Type 345. Pour in the top concrete cover to conceal the mesh wire, then leave the wet concrete to set and cure for at least 21 days.
Building Material Suppliers in South Africa
Major building material suppliers in South Africa include Builders Warehouse, CashBuild, Built-It and BUCO. There are also warehouses which specialize in one or two types of materials, like Pryde Hardware which makes timber trusses and all types of structural timber for roof and floor construction, including roof coverings such as cement tiles,Nutec roof slates, IBR and corrugated sheets of various materials such as zincalume, colorbond metal, galvanized steel, chromadek metal, polycarbonate and fibreglass.
Cost of Common/Standard Bricks and Blocks in South Africa
Builders Warehouse Bricks
Builders Warehouse [Builders.co.za] is probably the biggest building hardware store in South Africa in terms of variety of materials. Here you will find bricks of all types and size from clay to cement bricks, cape brick to Roma brick. Their store makes it easy to filter out bricks by their various characteristics and specifications such as compressive strength, mortar class, colour, length, product use, brand, type, brick class and structure type. This is a very useful feature which allows the customer to pick exactly what they are looking for.
A random survey of brick prices at the store is shown below:
- Plaster Brick – Stock Clay Brick (220 x100 x 70mm) – R1.80
- Face Brick – Brick Dapple Travertine (219 x 99 x 70mm) – R2.90
- Face Brick – Roma Bricks Cameo Rosso Dark Face Brick – R2.99
- Face Brick – Mutch Verona Yard Brick (220 x 110 x 70mm) – R2.75
- Face Brick – Roma Cameo Rosso Bricks (222 x 106 x 73mm) – R3.49
- 7Mpa Cement Stock Brick – R1.49
- 7Mpa Maxi Cement Brick (290 x 140 x 90mm) – R3.30
- Magnum M140 Concrete Block (140 x 190 x 390mm) – R7.85
- Load of Stock 12000 Clay Bricks (220 x 110 x 70mm) – R18,090 per load
- Load of Stock 7Mpa 14000 Cement Bricks – R18,110 per load
- Load of Stock 7Mpa 6000 Cement Bricks (220 x 110 x 70mm) – R7,760 per load
- Load of Stock 6000 Clay Bricks (220 x 110 x 70mm) – R9,250 per load
Bricks are not one of the best sellers at CashBuild stores due to the fact that they are not available or not supplied at all.
The store supplies hollow core concrete blocks but you have to request a quote.
There are several other places where you can get bricks and blocks, look for brick manufacturers in your area.
Cost of Cement in South Africa
Cement is sold in 50kg bags. The most common brands of cement in South Africa are Champion, SureCem, BotCem, Builders Warehouse, Build-It, SureBuild and OPC. The cement concrete strength specifications include class 42.5N and 32.5N. The price of cement depends on its brand, specifications and whether it’s manufactured locally or imported.
Builders Warehouse Cement
The store supplies large quantities of various types of cement brands including its own brand. A random survey of cement prices inside the store looks like this:
- AfriSam All Purpose 42.5N Cement (50kg) for concrete, mortar and plaster – R92.80
- Builders Warehouse General Purpose 32.5N Cement (50kg) – R69.00
- BOTCEM 32.5N Cement (50kg) for concrete, mortar and plaster – R N/A
Various brands of cement like Champion and SureCem are available from time to time. Cement is one of the most sought after items at CashBuild so don’t be surprised when it runs out of supply when you are looking for it. The store runs discount promotions on a regular basis, be sure to be one of the recipients.
- Champion 42.5N Cement (50kg) for building and civil engineering – R89.40
- SureCem General Purpose 32.5R Cement (50kg) – R81.10
The store has in stock its own brand of PPC 32.5N cement. You have to request a quotation.
Cost of Sand and Gravel in South Africa
Builders Warehouse Sand/Stone Aggregates
Among all the major building multi-material suppliers in SA, Builders Warehouse is the only store supplying sand , stone aggregates and dry concrete pre-mixes in large quantities. A random survey of prices at the store looks like this:
- Building Sand (Yard Sales) – R300 per cubic metre
- Plaster Sand (Yard Sales) – R430 per cubic metre
- 19mm Concrete Stone – White (1000kg) for foundations, surface beds and driveways – R285
- 13mm Stones (1000kg) – R560
- General Purpose Aggregates Stone (40kg) – R38
- Granite Stone (19mm) – R405 per cubic metre
- Granite Stone (13mm) – R425 per cubic metre
- Load of 6M3 Stone (19mm) – R2,800 per load
- Load of 6M3 Stone (13mm) – R2,800 per load
- Load of 10M3 Stone (19mm) – R4,550 per load
- Load of 10M3 Stone (13mm) – R4,550 per load
- Load of 4M3 Stone (19mm) – R2,200 per load
- Load of 4M3 Stone (13mm) – R2,100 per load
Please note that there are specialist suppliers whose sole trade is sand, aggregates and bricks where you can also get these items. Look for suppliers in your area.