What is a French Drain?

Septic tanks only partially treat the sewage and the function of the French drain is to provide the final treatment before disposal of the effluent.

The insitu percolation test should be conducted on all sites which are to receive French drains.

French drains should not be constructed on sites where:
·         the percolation rate is less than 30 minutes
·         effluent may flow out of the ground due to the contours of or the strata forming such sites
·         the level of the water table is or may be such to prevent adequate percolation
·         other sites may be affected by the presence of such a drain
·         there is insufficient space to accommodate the soaking away of the effluent

French drains should be sited and constructed so as to not to cause the pollution of nay public stream, spring, well or water source that is used, or that could be used for drinking, domestic or kitchen purposes.

They should be located downhill of a water source such as a borehole or spring.  Where the location of such a water source is not possible French drains should be located at least 50m from the water source.

French drains should be preferably constructed along the contour of the soil surface

Under floor membranes

Polyolefin membranes should be placed beneath all slab-on-the-ground foundations, irrespective of site and ground conditions.

The membranes should have a thickness of not less than 0.25mm and should be placed beneath the slab and beam thickenings so that the bottom surface in entirely laid.

Where justified by appropriate geotechnical conditions, the membrane as in the case of slab-on-the-ground features, may be terminated at the face or edge of the internal beam.

Lapping of membranes at joints should not be less than 200mm.

Penetrations by pipes, plumbing fittings or punctures should be taped with a pressure sensitive adhesive tape.

In the case of floor tabs, the membranes should be turned up around the perimeter of the floor slab by at least the thickness of the slab.

Compaction

The maximum height of fill beneath floor slabs and slab-on-the ground foundations measured at the lowest point should not exceed 400mm unless certified by the engineer.

Fill should be moistened prior to compaction so that a handful squeezed in the hand is firm but does not show signs of moisture. Fill should be placed in uncompacted layers not exceeding 100mm in respect of hand compaction or 150mm in respect of mechanical compaction.

Each uncompacted layer should be well compacted before additional fill material is added.

Compaction should be such that in excess of 3 blows of a dynamic cone penetometer are required to penetrate 100mm of the fill, provided that fills do not comprise more than 10% gravel size less than 10mm and contain no isolated boulders.

Dynamic (drop weight) cone penetrometer

This is an instrument used to measure the in situ shear resistance of soil comprising a drop weight of approximately 10 kg which falls through a height of 460mm and drives a cone having a maximum diameter of 20 mm (cone angle of 60 degrees) into the material used.

Our customers influence our performance objectives

We seek to satisfy customers through developing a few typical performance objectives.

When customers value our cost-effective pricing the operation will place emphasis on its cost performance.  If a customer insists on error-free services the operation will concentrate on its quality performance.  When a customer emphasizes fast delivery we will make speed important within the operation important while an emphasis on reliability will make dependability important.  When customers expect an innovative service, the operation must provide a high degree of flexibility in order to get its innovations to its customers before its rivals.  If a wide range of services are demanded by customers, the operation will need to be flexible enough to provide the necessary variety without excessive cost.

How well we meet your requirements is determined by how well our operation excels at these performance objectives which will subsequently influence the competitive factors.

Requirements of single storey masonry construction

·         The height of the wall from the floor level to the top of the external gable does not exceed 5.0 m

·         The span of roof trusses/rafters between supporting walls do not exceed 8.0m and for a concrete roof slab the restriction is at 7.0m

·         The dead load of the roof covering in a roof other than a concrete slab does not exceed 80 kg per square metre

·         Concrete roof slabs should not be thicker than 255mm if of solid construction or the equivalent mass if of voided construction

·         The height of the foundation walls should not exceed 1.5m

·         The height of the fill beneath the slabs should not exceed 1.0m

Assessing the risk associated with areas underlain by dolomites and limestones

A Competent person with engineering expertise shall investigate any proposed townships or existing township areas which are underlain by dolomites/limestones and shall prepare a clearly motivated report in which the township stability is zoned in terms of prevailing professional practice. The detail report must detail any precautionary measures which are required to reduce the risk of sinkhole formation/ subsidence and any restrictions of land usage, layout, erf sizes, density, services etc.  The report shall be submitted to the Council for Geoscience to obtain confirmation that these investigations are consistent with sound professional practice and the investigations meet all legal requirements pertaining to such stability investigations.

The report will included the impact of the stability of borehole installations and the construction of swimming pools and briefly outline the condition and nature of existing storm water systems and wet set services.  It should also specify any requirements or precautionary measures.

In townships zoned with precautionary measures (D2 and D3) where services have already been installed, the report shall outline where such services fail to meet the minimum requirements and to observe those precautionary measures set out.

This Competent Person should also liaise with the local authority under whose jurisdiction the proposed township lies and include a statement by such authority on their services risk management systems in dolomitic/limestone areas.  These statements must be signed by the relevant chief executive office and include the authority’s policy and procedures which it has in place in respect of the installation of bulk water and sewer services, measures to prevent land invasion on areas zoned as D4, maintenance of township services and enforcement of any special provisions and/or restrictions which may be imposed on individual erven.

In sectional title developments, we would prepare and submit a services risk management plan for inclusion in the constitution of the body corporate which is to be established together with a firm undertaking that this plan be incorporated in the constitution which is put before the first body corporate meeting for adoption.

Furthermore, the use of existing investigation reports on the township in order to reduce the amount of additional investigations is required if adequate and valid.

NHBRC’s approval prior to the installation of services in areas underlain by dolomites/limestones

The Home Builder must submit to the NHBRC a completed form countersigned by the Council for Geoscience, together with the local authority’s risk management statement, duly signed by their chief executive officer, and a report outlining the investigations undertaken and the basis upon which the zone designations are arrived at and a sanitation and storm water plan.  A formal request should be made to present proposals to the Technical Advisory Group of the NHBRC.

The NHBRC will modify the Home Builder of the time and date when he may make that presentation.

The Home Builder and Competent Person is responsible for preparing the submission and the Technical Advisory Group will subject the report and the sanitation water plans to a peer review, confirm or advise of amendments to the zoning and advise the NHBRC of their risk exposure in respect of the application.

The NHBRC shall then decide whether or not to enroll sites within the township, or portion thereof, on an individual site basis or deny enrollment from the outset.

Assessing the risk associated with areas underlain by dolomites and limestones

A Competent person with engineering expertise shall investigate any proposed townships or existing township areas which are underlain by dolomites/limestones and shall prepare a clearly motivated report in which the township stability is zoned in terms of prevailing professional practice. The detail report must detail any precautionary measures which are required  to reduce the risk of sinkhole formation/ subsidence and any restrictions of land usage, layout, erf sizes, density, services etc.  The report shall be submitted to the Council for Geoscience to obtain confirmation that these investigations are consistent with sound professional practice and the investigations meet all legal requirements pertaining to such stability investigations.

The report will included the impact of the stability of borehole installations and the construction of swimming pools and briefly outline the condition and nature of existing storm water systems and wet set services.   It should also specify any requirements or precautionary measures.

In townships zoned with precautionary measures (D2 and D3) where services have already been installed, the report shall outline where such services fail to meet the minimum requirements and to observe those precautionary measures set out.

This Competent Person should also liaise with the local authority under whose jurisdiction the proposed township lies and include a statement by such authority on their services risk management systems in dolomitic/limestone areas.  These statements must be signed by the relevant chief executive office and include the authority’s policy and procedures which it has in place in respect of the installation of bulk water and sewer services, measures to prevent land invasion on areas zoned as D4, maintenance of township services and enforcement of any special provisions and/or restrictions which may be imposed on individual erven.

In sectional title developments, we would prepare and submit a services risk management plan for inclusion in the constitution of the body corporate which is to be established together with a firm undertaking that this plan be incorporated in the constitution which is put before the first body corporate meeting for adoption.

Furthermore, the use of existing investigation reports on the township in order to reduce the amount of additional investigations is required if adequate and valid.

What are the exclusions from the NHBRC warranty?

The following are excluded from the Standard Home Building Warranty:

·         Willful acts or missions of the owner or tenant

·         Fire, explosion, lightning or damage caused by a third party

·         Storm, flood, frost or earthquake or any other convulsion of nature

·         Structural alterations, repairs, modifications or alterations which affected the original structure

·         Condensation

·         Subsidence or landslip from any cause not related to a defect in the foundations

·         Changes in colour, texture, opacity or staining or aging process

·         Pressure waves caused by aircraft or other aerial devices or damaged caused by them during impact

·         Loss of/or damage to any finishes

·         Wear and tear, deterioration caused by neglect or damage caused by the failure to report defects

·         Anything that could be reasonably rectified by the consumer

·         The electrical and plumbing systems

·         Misuse or abnormal use of the private drainage systems

How to fill foundations on slope sites

The site should be cut and filled, or terraced, with engineered fill to receive a slab-on-the-ground foundation or a strip footing. The fill should continue past the edge of the foundation wall or edge beam by at least 1000 mm and have a batter of not more than one horizontal unit to one vertical unit. The fill should then be retained or battered beyond this point by a slope not steeper than two horizontal units to one vertical unit. The interior of the slab as well as the edge beam or strip footing will be set on natural soil or engineered soil.
Or a deepened edge beam or a masonry foundation wall supported on a strip footing set below the natural ground level shall be provided on the interior of the structure to retained controlled or engineered fill. Deepened edge beams and steps in the floor at any change in level of slab-on-the-ground may be accommodated.

What is the warranty cover provided by the NHBRC?

During the construction phase the Home Builder will be required to provide the purchaser with a contract stating that the Home Builder will rectify, at his own expense, all latent as well as patent defects occurring during this phase. The construction phase begins from the date that the contract is effective until the occupation date.
During the first three months following occupation the Home Builder will rectify any deficiency related to workmanship and materials.
During the first twelve months of occupation the Home Builder will commit to repairing any leaks that occur.
The warranty period extends to five years in respect of any substructure, superstructure and roof structure repairs.

How unscrupulous contractors cut corners when pricing

Typically, an unscrupulous contractor may choose to leave out necessary items in the pricing.  This may be a contravention of the Building Regulations policies and pricing for sub-standard workmanship.  A clause to the RFQ should be added stating that all work must be done in accordance with the NBR to prevent them from claiming not to be aware of the regulations.

They would also choose to quote on sub-standard products.  It is subsequently the client’s duty to specify which brands to use or the desired level of quality.  Some contractors also tend to leave entire items out of lump sum prices.  Once the client itemized the work and set up a bill of quantities, it is harder for these contractors to leave sections of the work out without them knowing about it.

Generally’ clients need to protect themselves against contractor who cut their prices, items, procedures and processes they are pricing for just to get contracts and who will eventually charge them later during the latter stages of the project.

The role of the on-site project manager

Our project managers are a vital cog in the organization machinery. The project manager will be responsible for general liason between the field and the architect and owner, preparation of monthly statements for comparison with the budget, final check on monthly subcontractor requisitions, change orders and office correspondence regarding his projects and, of course, available at all times. He may even efficiently service two contracts concurrently with an assistant depending on the size and complexity of the work involved.
The project manager will probably be located in the field office. This would allow for a more unified control of the project and permits closer cooperation between the “inside” and “outside” and when the work is of sufficient proportion the full time service of an “inside man” will be required.
The project manager will be responsible for all activities on the site, starting with demolition, site engineering etc and continuing until the building is completed. Depending on the size of the project he will be aided by an assistant superintendent, one or more field engineers, one or more accountants and a paymaster, foreman, watchmen etc
The more important functions would be to check field engineering, monitoring time schedules, supervising all trades, checking quantity and quality of production, attending meetings with the architect and owner, collaborating with architect’s field representative, establishing sequence and coordination of operations and manning the project. He will also resolve disputes, supervise job meetings, maintain daily job diaries, complete insurance reports, check and approve sub contractors requisitions, order material and equipment and check equipment rentals.
In addition, he should maintain contact with the expenses department, keep a constant check on requirements of plans and specifications, check cost records and check and approve payrolls and guarding against construction accidents.