Note: for this unit I have mostly used references to the excellent website www.pavingexpert.com, it is very clear, with helpful photos and lots of information. However, I have also included my notes which are basically the information from pavingexpert pared down to the absolute essentials, since that can make it easier to get a framework of what to learn. For anyone studying Level 3 I would definitely advise reading the links as well.
1. Understand the practical procedures for setting out a site to scale plans and drawings.
1.1 Describe how scale drawings are interpreted to set out the major features of a design on the ground.
- Use plans (from above), profile (from side) and cross section (shows a slice through garden).
- On large projects use automatic levels and theodolites.
- On smaller projects – string line, spirit level, tape measure and marker pegs.
- Stake out relevant points and lines throughout the garden (eg a taut string line to show intended level of a patio, a spray painted cross to show where a tree is to be planted.)
- To establish a straight line hold string taut between two pegs.
- To mark points along a line, add a peg at the centre (touching, not bending string) and then pegs midpoint between existing pegs.
- A right angle is found with 3,4,5 triangle.
- Curves are created with an arc, using string held at a central point.
1.2 Describe how to set out the required levels on site.
- Setting out levels
- Video of datum levels (it’s for building, but still appropriate for garden levelling)
1.3 Describe the sequence of works involved in the realisation of a design.
- Repair and pruning to be done
- Soil condition
- Health and safety
- The site compared to the plans
- Access and storage
- Risk assessments (carry out)
- Clearance (of any rubbish, unwanted plants)
- Contouring (including ponds)
- Services (working out location and working around them)
- Landscape features set out
- Foundations (for vertical and then horizontal landscaping)
- Finish ponds
- Construct features
- Finish contouring
- Ground preparation and soil improvement
- Turf laying
- Final checks
2. Understand the reasons for correct soil movement and storage during construction works.
2.1 Describe the correct handling, storage and reinstatement of soil during site construction; to include separation, angle of repose and maintenance of soil quality during storage.
When making major changes to a garden, especially building and contouring, it is important to remove the topsoil first so that it can be stored elsewhere to ensure it remains undamaged and doesn’t get mixed with subsoil. When all construction and levelling is finished, the topsoil can be reinstated, ready to be planted.
Topsoil is better for plants than subsoil, it contains more nutrients, has a better structure and contains helpful soil organisms, if topsoil and subsoil become mixed, then plants will not grow as well.
Construction is damaging to topsoil because heavy machinery causes compaction and damages the structure in a soil. Building also tends to result in rubble, dust and chemicals landing on soil, so removing topsoil stops these from contaminating soil and harming plants.
Angle of repose
This is the angle at which a pile of soil is stable, it is 45°, unless the soil is to be seeded with grass, in which case it is 25°.
If soil is stored for longer than 2 weeks, the centre becomes anaerobic, if the soil has been stockpiled well it will revert to aerobic when spread, but if it has not, then structure will be spoiled.
Stockpiles should not be near roots of trees, next to ditches, watercourses or future excavations.
If the storage is long term (6 months) then seed with grass or a green manure to stop weeds.
Soil should be stored dry (non plastic), because:
- It is less prone to compaction
- It retains structure
- It re-spreads easily
- It easily breaks down to a fine tilth
- It can be stored in a larger pile (3-4m high)
2.2 Describe the procedures required to reinstate the soil to the levels specified in the design.
Machinery for Reinstating Soil
- Spade and wheelbarrow for small garden.
- Digger or mini excavator for slightly larger sites.
- Backhoe digger/ JCB for large sites.
- CAD packages (computer aided design) can be used to quantify amount of soil needed to be cut from one area to build up another,
Process to Create Levels in the Garden
- Remove topsoil and store as described above
- Calculate and mark out levels
- Dig out subsoil to levels required (eg 30cm lower than the final level needed)
- Use surplus subsoil to build up higher areas
- Cover with topsoil to an even depth
2.3 Describe how biosecurity measures are used to prevent the distribution of pests and diseases through soil handling/storage and reinstatement.
Storage of soil should not be in a contaminated area (eg where there has been phytophthora) or from a contaminated area to a non contaminated one. It’s important to stop weeds growing in stored soil, since weeds can encourage both pests and diseases. Soil stored wet is also more likely to encourage fungal disease.
When buying topsoil in it must conform to British Standards and the following questions asked to determine that the soil is free of pest and disease:
- Where does the soil come from?
- Is it stored in an area protected from the elements?
- Is it free of Fallopia japonica?
- Is it manufactured or naturally occurring?
- How is it delivered?
- Has it been tested for PTE (potentially toxic elements)
- Will it be workable as soon as delivered?
3. Understand the factors which determine the type of drainage system required in various situations.
3.1 Describe the construction of an intercept or French drain to collect run-off, a pipe drain system to lower the water table and a soakaway to drain a localised wet area.
- Dig trench 25cm wide, 90cm deep.
- Trench is lined with geotextile.
- 10cm layer of pea gravel.
- Add drain – perforated pipe.
- Back fill with pea gravel.
- Soakaways allow water to be released to surroundings slowly.
- A hole is dug 130cmx130cm wide and 160cm deep.
- At least 5m away from any building.
- 1cm layer of gravel in bottom.
- Line hole with geotextile.
- Place cells (like crates) into hole.
- Wrap geotextile around cells.
- A PVC pipe is lain so that it enters the cells.
- Cover with 10cm of gravel and then topsoil.
4. Know materials and construction procedures for paths, patios and driveways for parking and light use.
For materials see previous blog, unit 1.1
For procedures see following units in this blog
4.1 Define the terms ‘flexible’, ‘rigid’ and ‘permeable’ in relation to paving.
4.2 Describe a range of appropriate surface materials for paths, patios and driveways for parking and light use. To include: concrete, gravel, bricks, block paving, natural and artificial stone and paving.
For materials see previous blog, unit 1.1
4.3 Specify appropriate foundations for (i) a concrete path, (ii) an aggregate driveway (iii) a slab or natural stone patio (iv) a permeable hard-standing area.
4.4 Outline the procedures for preparing the site and laying foundations for the situations mentioned in 4.3.
4.5 Outline the procedures for laying the surface materials mentioned in 4.2.
4.6 Specify appropriate edging materials for the situations outlined in 4.3 and describe their installation.
Constructing a concrete path (including foundations)
- Excavate to 10cm.
- Build temporary formwork.
- Lay damp proof membrane.
- Mix cement with 1 cement : 2 sand : 3 gravel.
- Level with strong rake or shovel.
- Tamp down using straight edged timber.
- Finish – done as concrete starts to harden, use steel float trowel.
- Cure by keeping moist or covering.
Gravel driveway construction (including foundations)
- Decide where driveway is to run and mark out.
- Dig to a depth of 10cm.
- Remove all weeds from the area, use weed killer if serious problem or use geo membrane.
- Install edging – timber gravel boards – stakes hammered into ground using line to keep straight, rails nailed to stakes.
- 5cm of sub base DTp1.
- 1 tonne of DTp1 granular sub-base covers approx 6-8 m² at 7.5cm compacted thickness.
- 5-4cm gravel.
Natural Stone Patio
Patio construction (including foundations)
- Dry lay patio to check how it is going look and that there are enough slabs.
- Be sure slabs are the right way up – flags taper inwards so top surface larger than lower.
- Dig out 15cm deep.
- Fall of 1:60.
- 6:1 ballast:cement cover hole to depth of 7.5cm.
- Lay mortar bed of 6:1 sand:cement.
- Set up 2 taut string lines to guide line and level, including drainage fall.
- Use rubber mallet to tamp down slab, tap all corners until at correct height.
- Use spirit level to check levels.
- Leave for 24 hours to harden.
- Mix mortar 3: sand to cement and trowel into joints.
4.7 Describe the construction of an area of permeable hard standing (to include reinforced grass and permeable paving).
Permeable Hard Standing
- Ground is dug out and edge restraints (paving on edge) are concreted in, with 10cm of concrete below.
- Permeable geotextile is used to line the pavement.
- Sub base of coarse graded aggregate to 30cm depth is poured in by digger and raked out level.
- Then compacted with vibrating plate.
- Then finer aggregate is poured in to 5cm.
- Special permeable paving blocks are then lain.
- Blocks compacted in, then jointed with grit.
Most of the above links talk about edging, but here are some extra pages:
5. Know materials and construction procedures for steps and ramps.
5.1 Specify appropriate foundations for one step and one ramp.
5.2 Specify two appropriate materials for a step and two for a ramp.
Ramp – aluminium, cedar
Steps – bricks and stone flags
5.3 Describe the construction of one type of step and one type of ramp.
Steps (built on a slope)
- Mark out site using line and pegs, check right angles.
- To work out how many steps needed measure vertical height and horizontal distance of steps (use spirit level).
- Strip away turf from marked out area.
- Roughly shape the steps with a spade.
- Footing for first riser is 12.5cm deep trench, fill with concrete, leave for 24hrs.
- Mix mortar using 4:1 sand to cement.
- Build two layers of brick in stretcher bond – check with spirit level.
- Fill behind first step with hardcore up to top step.
- Lay bed of mortar on hardcore and put on stone slabs.
- Fill in joints with mortar.
- Build next riser on lower- tread and keep on building up steps.
- Dig hole for corner posts and pour in concrete.
- Attach anchoring brackets to attach rails to (across the ramp).
- Aluminium sheets are nailed across the rails.
- Ramps should be a minimum of 90cm wide and have a fall of 1:12-1:16.
6. Know materials and construction procedures for low garden walls, retaining walls, fences and pergolas.
6.1 Specify materials suitable for the construction of the following: (i) a single-skin garden wall; (ii) a double-skinned or retaining garden wall; (iii) a low wall for a raised bed; (iv) one modular fence; (v) one non-modular fence and (vi) a pergola.
6.2 Outline procedures for erecting: (i) a retaining garden wall; (ii) a low wall for a raised bed; (iii) a fence; (iv) a pergola.
6.3 Specify foundations (where appropriate) for each of the constructions named in 6.1.
Single skin Garden Wall
Garden walls (single, double and retaining)
A single skin wall is the width of one brick width.
- Dig a trench to 25cm below ground and for 10cm either side of the brick width.
- Pour in a concrete footing, depth of 10cm.
- The wall goes 15cm deep into the ground, mark out where it will be built.
- Start with corners and ends first.
- Mortar is 6:1 sand:cement, not too sloppy.
- Jointing can be flushed, weathered, rubbed or recessed.
- Check levels while building and ensure the wall does not belly out.
- Damp proof course is 15cm above ground.
- Once the wall is the desired height, add coping.
Double skinned or Retaining Wall
A retaining garden wall is one that supports the weight of soil on one side. To build it the rules are similar to above, however the footing needs to be stronger and it’s important to include features that prevent damage from damp that can be caused buy the soil.
- The concrete footing is 15cm deep.
- An impermeable drainage board is attached to the retaining side of the wall.
- Pea gravel is against the drainage board.
- An 8cm land drain is inserted into the pea gravel.
- A permeable geotextile holds in the gravel.
- A 1.5cm copper pipe is inserted into the wall.
Low Wall for Raised Bed
Materials for a raised bed wall can be railway sleepers, steel or brick
- A concrete foundation 5-10cm deep can used for the foundations, alternatively gravel which is better for drainage.
- Lay the sleepers on top of the foundation, staggers the joints, like building a brick wall.
- Fasten each layer to the layer below with screws.
- Set up taut string line and measure where posts will go – 1.8m apart.
- Dig hole for posts 30cmx30cm and for 1.2 m high fence, 5.5cm below ground.
- Mark on post where ground level should be.
- Put 5cm concrete in ground and lower post onto it to required depth.
- Align post vertically and jam in bricks to keep steady.
- Fill in with dry mix concrete and add water.
- Panelling is then slotted into place.
- Dig holes 30x30cm depth of 50cm.
- Concrete in posts to depth of 45cm – with 5cm concrete at base.
- Let concrete set over night.
- Attach side rails with inline braces – rails nailed to posts and braces.
- Attach cross members.
- Attach traverse braces.
7. Know materials and construction procedures for a water feature.
7.1 Specify suitable materials for the construction of (i) a formal pond (ii) an informal pond.
7.2 Outline the procedures for constructing (i) a formal pond (ii) an informal pond.
8. Know materials and construction procedures for a rock garden.
8.1 Specify a range of materials suitable for the construction of a rock garden.
8.2 Specify an appropriate method for the construction of a rock garden.
- Dig out topsoil and add in a mixture of grit, sand and leaf mould
- Dig in boulders two thirds above ground, one third below
- Large boulders first
9. Understand risk assessments.
9.1 Determine the elements of risk in operations associated with this unit.
Some risks associated with building and garden restructure:
- Slips trips and falls – avoided by keeping paths clear, clearing up spillages, using signs around holes in the ground.
- Injury from hand tools and machinery – all gardeners to have proper training and fully working tools and machinery, and PPE (eg goggles and gloves).
- Damage to people and property by vehicles – use vehicles with good visibility, make sure to close off all dangerous areas to the public, vehicles only driven by fully licensed staff.
- Damage to services (water pipes, electricity and gas) leading to injury – ascertain where services are before starting.
- Long term physical injury such as bad backs, knees etc – staff to use proper lifting techniques and observe limits, to receive training as necessary.
It’s also important to plan emergency exit routes before starting and have a first aid kit on site (having a first aider is even better).