Materials

Cement Use only Cem 1 and Cem 2 grade cement to mix with your aggregate. Lower grades will not develop the necessary structural strength. A 32.5 MPa cement is adequate. The 42.5 MPa cements will dry a bit faster and allow you to do the next FinnBUILDER row a little sooner.
Aggregate A good aggregate contains a range of materials; from concrete stone to coarse material where the biggest particles are no bigger than 5 mm in size, down to a fine material where the biggest particles are no bigger than 1 mm in size. Very little water is used in the mix to enable the slip form system of moving shuttering to be effective; and to achieve high strength.
  • A 13 mm concrete stone enables the concrete to develop strength without the roughness of using larger stone
  • River sand is a good coarse material if it is not too washed. If a good river sand is not available in your area, consider using a 13 mm crusher dust with a good range of particles in it from 13 mm all the way down to 1 mm.
  • Building sand is a good fine material which will help give a smooth off-shutter finish and ensure that plastering is not necessary.
Water Use only clean drinking water. Cement will not gain the required strength if brackish water is used.
Use your own on site soil Many people who built in the country do not have a quarry close at hand. In these situations we recommend using your own on site soil, or material in your immediate vicinity.
In the Details Construction Guide, which comes with the machines, we have included a test devised by the Cement and Concrete Institute of South Africa which allows you to test soil and determine whether it is suitable for use as a building sand. In some cases you will want to add some concrete stone to the soil to give you a suitable aggregate. If you are able to use your own soil, this will substantially reduce costs even further.
Rapid hardening agents You can use a cement pre-mix such as “Drikon” which will accelerate the drying time of the cement if you need to build vertically quickly. Pre-mixes will accelerate the usual drying time by one hour.
CONCRETE MIXES
There are a variety of concrete mixes shown in the Detailed Construction Guide that comes with the machines which may be used for different applications and depending on the materials available in your immediate area.
The most common used 15 to 20 MPa mix is:

2 x Building sand (2 wheelbarrows)
1 x Cement (2 pockets of 32.5) (2 pockets of cement)
30ltr x Water (30 liters of water)


CONCRETE STRENGTHS

Recommended mixes detailed in the Construction Guide are:

Perimeter wall under 1.8m high, shed, bird or small animal enclosure 5 – 10 MPa
Perimeter wall over 1.8m high 0 – 15 MPa
Single and double storey houses (depending on the wind loading) 15 – 20 MPa
Reservoirs and large animal enclosures 20 – 25 MPa
Retaining walls 25 – 30 MPa

MATERIAL USAGE

One of the biggest attractions of using FinnBUILDER™ is that it is a lot less expensive than building with brick or blocks. See Cost Comparisons for further detail on this. You can calculate the amount of material that you need to use following this simple guide:

1. Decide whether your walls will be 220 mm thick, 150 mm thick or 110 mm thick.
2. From your plans, measure the length of you walls and the height.
Calculate the area of your walls by multiplying the length by the height. e.g. if the wall is 50 meters long and 2 meters high, the area of the wall is 100 m2. A cement pocket weights 50kgs and costs about R 70.00 each

Calculate quantities required and cost based on wall of 100m2

Tickness of wall
Aggregate needed / m2
Cement needed / m2
Total aggregate needed
Total cement needed
Cost of aggregate @ R150 / m3
Cost of cement @ R70 / pkt.
220mm
0.253m3
43kg
= 25.3m3
= 86 pkts
= R 3 795
= R 6 020
150mm
0.13m3
29kg
= 17.3m3
= 58 pkts
= R 2 595
= R 4 060
110mm
0.127m3
21kg
= 12.7m3
= 42 pkts
= R 1 905
= R 2 940

Total aggregate needed will be divided up on the ratio of the mix that you have elected to use as per the Detailed Construction Guide.

DOUBLE STOREY HOMES

Since 1946 double storey homes have been built using FinnBUILDER. Examples are shown in the Gallery.

FOUNDATIONS

The plans for your house or structure must be drawn by a qualified architect or architectural designer, who will need a Civil Engineer to specify the type and thickness of the foundations that you need to pour, given your soil conditions and the loadings that your structure will carry. Generally foundation trenches will be a minimum of 600mm deep below natural ground level (NGL), and 650mm wide for external walls and 450mm wide for internal walls.

Foundations are a critical part of any building. If you are not a civil engineer, make sure that you have dug your foundation trenches down to firm footing throughout the trenches, and then call in the Municipal Inspector and the professional engineer to inspect your foundation trenches and approve them before you throw your concrete.

Once your foundation trenches have been approved, use a foundation concrete mix of 3 wheelbarrows 19mm concrete stone, 3 wheelbarrows of river sand and 2 pockets of cement plus 80 liters of water to throw your foundations 200mm thick. Double storey foundations will vary in depth.

Retaining walls can be inexpensively built using the system. Once again the design of the wall is a technical issue which must be properly addressed by a professional engineer. Vertical steel running out of the foundations and into the wall, structural piers and adequate drainage ports are some of the design elements which needs to be considered.

SABS TESTING

SABS testing has taken place on our concrete mixes to confirm that they achieve the required strength.

NHBRC

The NHBRC is now the watchdog of the building industry and under new legislation during the last fifteen years, new building projects have to be approved and enrolled with the council before bank financing can be granted.

The NHBRC has approved our FinnBUILDER RATIONAL DESIGN and will enroll sites that will be building using the system. The requirements of the NHBRC include the appointment of a Competent Person to monitor construction with the QUALITY MANAGEMENT SYSTEM and who will be responsible for signing off that the building has been built in accordance with the RATIONAL DESIGN.

MUNICIPAL REQUIREMENTS

Once the requirements of the NHBRC have been met, Municipalities in South Africa will accept your plans. If they have further questions, you are welcome to refer them to ourselves so that we can answer any further technical questions that they may have.

The plans that you submit to the Municipality to specify that you will be building with “slip form concrete shuttering, using 15MPa no-slump concrete”.

AGREMENT CERTIFICATION

Now that we have full NHBRC Accreditation, it is no longer necessary for us to persue Agrement Certification. The system already enjoys acceptance throughout Africa and many other countries in the world. For this reason we are no longer persuing Agrement Certification.