Building design is the process of taking a client’s requirements for a new construction or changes to an existing building and translating them into an agreed design that a contractor is then able to erect.
Building design also refers to the architectural, engineering and technical aspects of designing structures.
To design a building, architects must first understand what the client wants from the project. They then do the designs and develop blueprints using computer software such as AutoCAD, Revit, ArchiCAD etc.
In these designs they can include a determination on the best materials and methods for constructing the building. When there is need, especially in large buildings, engineers then develop structural drawings where they carry out stress calculations to determine load bearing methods for the structure.
This article shall seek to explain and simplify information as contained in Chapter 2 of “The Model Building By-laws.”
Plans and drawings
There are different types of drawings used in construction eg, architectural drawings; structural drawings; site plans; sewerage and drainage plans. A plan is required for construction of a new building; re-erection or changes in a building; and for sewerage works.
It is a pre-requisite that before any works are commenced there be a plan approved by the local authority. However, there are no approvals needed for anything done or changes effected within the boundaries prescribed on any site e.g.
Maintenance, repair or redecoration of any building, plumbing system or sewerage system
Provision of extra taps or branches in a water distribution system
Additions and adjustments of rooms within the boundaries
These plans should be done by a competent architect or engineer and must be done in terms of the bye laws. Drawing is a universal language which uses notation that can easily be interpreted by any competent person. All plans should be dated and signed by the one responsible for their preparation
These are mainly prepared by architects, engineers or other competent persons. The architectural drawing shall comprise the following
A complete set of working drawings
Plans and sections of any sewerage and drainage work to be undertaken
A statement of the proposed use of all the various parts of the proposed building eg, proposed main house on stand number 33162 Caledonia township.
Working drawings shall consist of as many plans, sections and elevations as may be necessary to fully and clearly show the position, form, dimensions and materials of every part of the building intended to be erected.
According to chapter 2 Section 14 subsection 2, for working drawings to be considered for approval by the local authority must depict the following among others
Position and dimensions of foundations (and pilings if any); all floors, walls, windows, doors, stairs, roofs and chimneys
All sanitary fittings layout
Outline of all structural members such as columns, slabs, beams, trusses, etc., details of which are usually contained in structural drawings
Intended use of every room or compartment and for public buildings and those intended for use as place of indoor assembly, the maximum number of persons allowed and details to the seating and aisles respectively
Details of intended permanent earthworks affecting the buildings intended to be erected
The levels of the floors relative to one another and in relation to existing ground surface and proposed finished ground surface
All provisions made in the design of the building for proposed future additions
Position of any permanent fire extinguishing equipment to be installed
Section 13 deals with site plans. Site plans are expected to fully and clearly show the following information
a) Dimensions and boundaries of the site
b) Particulars about the location of the site indicating name of street and stand number, widths of building lines; and widths of any roads servitude
c) Nature and position of all natural watercourses or other natural features like rocks and cliffs which may result in changes of ground level
d) Nature and position of all sewers, drains, water mains, cables and any structures supporting or connected to the building to be erected
e) Nature and position of all building lines and servitudes associated eg, sewer, water, electrical cables
f) Location upon the site of every building to be erected or altered; any existing buildings on site; positions of connections such as water and sewer connections; and proposed vehicle entrances to the site
g) Distances of the buildings on the site from one another and from site boundaries
h) Direction of the true north
Every building or portion of thereof is designed and constructed to sustain the most adverse conditions of dead loads, superimposed loads and forces — which it’s expected to be subjected to.
These loads and forces are expected to produce adverse conditions of induced stress, deflection and structural instability. Where a structure requires such stress calculations, structural drawings have to be prepared by a qualified and competent engineer.
The structural drawing, usually done after the architectural drawing should depict all structural members such as columns, slabs, beams, joists, rafters, trusses, battens, purlins, etc.
The drawings give details of all reinforcements and concrete grades for concrete works such as beams, columns and slabs. For steelworks it also provides details on the layout and materials for structural members and their supports. It also highlights details about special foundations and reinforced footings where there is need
Sewerage and drainage plans
It should contain as many plans, sections and elevations as may be necessary to clearly show full particulars of all intended and existing sewers and sanitary fittings. The drawing should contain information on:
All existing and proposed drains
Proposed arrangements for discharge of rainwater from building and its site
The size, depth and position of every private sewer
Size and position of every manhole, means of inspection, rodding way, gully trap, etc.
The gradient in figures of sewer or drain and any change in gradient of sewer or drain
Material with which all sewers, pipes and vents are constructed
Relative levels of the sewer points, pipes, fittings and connections to the ground or to a datum level
The drawing should contain standard notation such as
a) rw – rodding way
b) svp – soil vent pipe
c) wc – Water closet etc.
Submission and approval of plans
Before commencement of works, drawings should be approved by the local authority upon payment of a prescribed fee. One should ensure that the plans being submitted for approval are accurate and should not contain false information. Before approval, the local authority checks the plan’s compliance to the following:
1) Compliance with the conditions of the tittle of the premises concerned
2) Compliance to any town planning schemes e.g., water, sewer and roads
3) Compliance to public health requirements
4) Provisions of the by-laws and any other law
If plans have been rejected, the applicant is notified of any amendments or adjustments required of the plan to obtain compliance and this has to be done in a specified period which if lapses, the local authority may give notice that his plans have been rejected.
An approved architectural drawing doesn’t serve as a structural drawing. Before commencement of structural works such as steelworks, framework or reinforced concrete works, structural detail drawings must first be prepared by a qualified engineer and approved by the local authority.
When a plan has been approved, a copy is retained by the local authority while another is retained by the applicant and kept on site. Plans submitted for approval include plans for new work; and plans for alterations, additions and partial re-erections
Plan production specifications
Section 10 to 12 deals with specifications on paper material, scales and colours pertaining to plans
Material: the standard sheets upon which the plans should be prepared are A0, A1, A2, or A3. The print should be on white paper or other material approved by the local authority. For longevity, the paper can be laminated
Scales: the scale should be clearly stated on the drawing. One should select a suitable scale that makes the drawing to be drawn legibly with all details visible.
Examples of commonly used scales are 1:100; 1:200; 1:500; 1:1000; etc.
Colours on plans: the drawing should have colours that increase visibility of detail e.g., on a site plan the following standard colours can be used
Areas of proposed work – red
Work to be demolished – uncoloured and outlined with black dotted lines
New private sewers – brown
Innocent Chatikobo is an Engineer by profession with AtroServe Engineering Zimbabwe. He has extensive knowledge and experience in Structural Engineering and Construction. For your comments, views, questions and feedback he can be contacted on the following platforms/Cell: +263 777 950 224; +263 712 376 037; +263 782 502 732/Email: [email protected] /Facebook: AtroServe Engineering Zimbabwe