This is where the clients start to get nervous
The process is noisy and dirty and will annoy babies and dogs and the occasional neighbour.
It is important for the builder/supervisor to be on site during excavation.
- Underground obstacles sometimes are found and decisions need to be made immediately.
- We normally allow a full day to excavate a standard swimming pool.
- Machines are usually bobcat excavators and backhoe excavators.
- A standard skid excavator requires 2.0m width for access and under 2.0m height.
- Access to the pool area determines which machine is best for the task.
- Smaller machine are available but obviously are slower to excavate a pool and will be more expensive.
- Hand dig may be required if access width is less than 1.2m between house and boundary.
- We have special small excavators for machine assisted hand digs.
- This option is an extra cost and accounts for 25% of modern homes on small blocks.
- A small machine may not reach high enough to load a tip truck.
- We still require a bobcat to place the soil into the truck so there is some double handling.
Tip fees and Cartage
- The average family pool requires around 6 truckloads of soil to remove.
- Tip fees and cartage costs are unique to each home location so this is usually priced separately.
- The cartage is a function of distance to a dump site.
- Tip fees are based on the tip site charges.
- The fairest costing method is a cost plus basis so the client is presented with the actual cartage and tip fee dockets and everything is open and honest.
- At point of sale as reasonable estimate should be possible for tip and cartage fees and a provisional sum included in the contract.
- The excavated hole will be approximately 1.0m longer and 1.0m wider than the actual finished pool dimensions.
- The depth will also be approximately 400mm deeper than the finished pool.
- The concrete shell subject to the specific engineer drawings will be 200mm thick throughout the walls and floor.
- Temporary safety fencing or barriers should be considered by the client.
Backfill after the concrete shell
- It normally takes at least one week to build a concrete pool shell.
- The shell then needs at least two weeks to cure before soil back fill.
- The earthworks can continue after the concrete shell has cured.
- Backfill soil can be placed by machine if access is available or placed by hand.
- The backfill soil is washed in and compacted all around the shell.
- Installation of pipes and underground fittings tales place at this stage and the site cleaned up.
- Engineers will advise that excavation should not be closer to an existing building or retaining wall than the depth of pool dimension.
- So if the pool is planned to be 1.8m deep we should not dig closer to the building than 1.8m.
- Many small width properties would not then be able to have a pool.
- To preserve existing structures during excavation soil stabilization may be required.
Chemical grouting before excavation
- To enable excavation up to walls and boundaries we use chemical grouting.
- Special liquid cement is pumped into the soil before excavation to make the soil hard down to about 1.5m
- This enables excavation to be closer to buildings and boundaries than the pool depth.
- This is an additional cost but will enable pools to be built to maximum size in a small area.