Q4. Describe the groundwork procedures prior to the installation of a permeable car parking surface under the following headings:
i) ground preparation; 3 marks
ii) appropriate foundations; 3 marks
iii) installation of ONE NAMED edging material. 4 marks
NOT TO INCLUDE SETTING OUT OR INSTALLATION OF THE SURFACE MATERIAL
This question relates to the following parts of the syllabus:
Outcome 3. Understand the reasons for correct groundwork procedures.
3.3 Describe the foundations for hard landscaping
State the purposes of foundations.
Preparing the site prior to the installation of foundations to include where, appropriate:
- subgrade; - formation level; - membranes; - consolidation; - dimensions.
Describe appropriate foundations for:
- an in-situ concrete path; - an aggregate/gravel driveway; - a concrete slab patio; - a permeable car parking area; - a low, brick freestanding garden wall; - a concrete block retaining garden wall; - a panel fence; - a pergola.
Outcome 4. Know materials and construction procedures for garden surfaces.
4.1 Describe a range of appropriate materials for garden surfaces.
To include: paths, seating areas, driveways (for parking and light use), steps and ramps.
To include: concrete (in-situ, units), gravels (chippings/shingle, self-binding), clay pavers/bricks, natural stone, timber decking.
Edging as appropriate to include: wood, brick, precast concrete, natural stone.
Specifications to include as appropriate: colour, dimensions, surface finish, durability, maintenance requirements.
Sustainability issues (e.g. reuse, recycling, reclamation, carbon footprint).
Define the terms ‘flexible’ (e.g. block paving, gravels), ‘rigid’ (e.g. in-situ concrete).
Define the term ‘permeable’ in relation to hard surfaces (e.g. specialised blocks, grasscrete and gravels). Significance of planning law relating to Sustainable Urban Drainage Systems (SUDS).
4.2 Describe the procedures for laying the surface materials mentioned in 4.1.
Describe the construction of:
- an in-situ concrete path; - a block paved driveway; - an aggregate/gravel driveway; - a concrete slab patio; - a permeable car parking area; - a short flight of steps; - a ramp.
To include edging for the above as appropriate.
There are several things you need to be clear about for this type of question. It can be a good idea to underline the feature you need to describe in the main part of the question – i.e. a permeable car parking surface. Then you need to be clear about the stages that are required. Take note of the part in bold at the end about what is not required in the answer. The examiners’ comments state that many candidates wasted time including information about the choice of surface material, setting out and installation of the surface material.
For part i) ground preparation, the examiners’ comments suggest the following:
· removal of debris and existing vegetation with a suitable method and equipment (e.g. mini digger, use of herbicides etc.)
· removal of topsoil and excavation to an appropriate formation layer
· consolidation of the sub grade/subsoil and the required equipment (e.g. plate compactor)
Always take a logical approach to answers working through the different stages in the correct order.
For part ii) foundations, the following is suggested:
· inclusion of a geotextile membrane – permeable to allow passage of water but avoidance of migration of the sub-grade into the foundations.
· Installation of a suitable permeable base material – e.g. DoT (MOT) type 3, no fines ‘’hardcore’’.
· To an appropriate thickness suitable for light vehicular traffic – e.g. 150mm minimum.
· Consolidation/equipment (e.g. plate compactor).
The examiners’ comments mention that the position and purpose of the membrane weren’t always understood. This part all needs to take notice of the permeable nature of the car parking area. The base material selected is important for this permeability.
The last part is the installation of the edging material, so it is important not to confuse this with putting down the surface material.
The examiners’ comments suggest the following:
· Material – e.g. precast concrete kerbs (described with appropriate dimensions, e.g. bull nosed or round top 50mm x 150mm)
· Laid in stiff concrete with correct mix (1:5)
· Dimensions given and haunched/shouldering to rear (better answers had a diagram)
· Laying technique to a set out line
· Joints dealt with appropriately e.g. butted
It can be seen that accurate detail will gain higher marks for these questions, but a logical description of appropriate methods is also very important.