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20-22 Wenlock Road, London N1 7GU

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020 3372 4482

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Mob: Call or Text to 07557 966 459

84 Brown St, Salisbury SP1 2BA

Tel

01722 504818

Shotcrete / Gunite Swimming Pool Installation

Absolutely Stunning Pools can be built using Shotcrete - click on pic for bigger image:-

 

amazing pools can be built using shotcrete

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How do they Work?

Well it looks like this:-

 

shotcrete in progress

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Basic Principles

Shotcrete is a process where a 200mm thick pool shell is formed in the following steps:-

  1. The excavation for the pool is carried out as accurately as possible on an alignment that is exactly 200mm larger than the required internal dimensions of the swimming pool (so the excavation for a 10m x 5m x 1.5m deep pool would be 10.4m x 5.4m x 1.7m deep)

  2. The top of the pool is always placed slightly proud of the surrounding ground so that the deck paving around the pool sheds rainwater away from the pool. So a plywood shutter is fixed on the exact alignment of the outside face of the top of the pool walls

  3. High Tensile reinforcing bars are placed in a cage that has been designed by a Structural Engineer to suit the pool size and the subsoil conditions that are present at the pool site

  4. The Plumber fits the skimmers, inlets, vacuum point, main drains and the pipework and supports these items from the reinforcing cage and the shutter

  5. The Shotcrete crew then use a high pressure pump that pumps wet concrete to a nozzle that is hand-held in pool construction. At the nozzle compressed air is introduced along a tube from an air compressor and this blows the wet concrete onto the surface that the nozzle is pointed at. The nozzleman is the most important person in the process because a lot of skill is required to continuously change the nozzle settings so that high quality concrete is created. In pool construction there are several other people in the team that carry out the final shaping the concrete with trowels so that it is suitable for either the render or a render and tiled surface.

  6. The pool shell needs to be left to cure for a period before finishes are applied.

In cross-section the pool shell looks like this:-

 

typical shotcrete pool wall cross-section

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When ready-mixed concrete from a batching plant is not available or is too far away the Gunite process can also be used to produce equal or perhaps better quality concrete. The process is similar except that the wet concrete is replaced with a dry mix of sand and cement that is blown to the nozzle with compressed air where it is mixed with water at the nozzle.

The equipment required on site looks like this:-

 

 

shotcrete installation plant

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Officially these are known as the “Wet” and “Dry” processes but generally “Shotcrete” is the name applied to the wet process and Gunite the dry process.

It is interesting that in the US Bluepools makes the choice purely on the basis of price – in some areas cement is so much cheaper then ready-mixed concrete that several thousand dollars can be saved by going down the “Dry” or Gunite route.


Shotcrete in the UK

The use of Shotcrete is widespread in the UK in the tunnelling and other civil engineering applications and so there are a large number of highly experienced firms that each have 6 or more teams operating.

This means that the industry is very competitive and economic prices can be obtained for swimming pool construction in most areas of the UK.

So when Bluepools recommends a Shotcrete pool an extra Trade Contractor is required – the Shotcrete contractor.

The main risk of a shotcrete contract going wrong is when the excavation for the pool is over-dug and the Client ends up paying for the extra excavation as well as the extra Shotcrete required to fill the void.

The best way to avoid this risk is to include the excavation in the Shotcrete contractors quote – this may end being a bit more costly but the whole risk of the volume of concrete used is then left with the Shotcrete contractor.

There is a common misconception that Shotcrete pools are very costly.

This may be true under some circumstances but if a firm fixed contract price from a reputable Shotcrete contractor is on the table and is compared with a costly vinyl liner kit where the time of and cost of installation is on a cost-plus basis it will be much less risky than the vinyl liner pool wall kit.

And of course from a structural point of view there will always be some risk with a pool wall kit – but none at all if a Shotcrete pool is chosen.


You may need to install a Shotcrete pool - if your home is in a swelling clay area

If your property is in an area with swelling clay then the first choice of pool type should be Shotcrete. More information about swelling clays and their location is shown on this link:-

http://www.bgs.ac.uk/science/landUseAndDevelopment/shallow_geohazards/whatisShrinkSwell.html

Will Witt has carried out many investigation into pools that have been lifted by swelling clays.

Most of these pools were built by very reputable pool installers using normal pool installation procedures and they were all really taken aback when the problem was explained to them.

It is far preferable to install a pool using the Shotcrete Installation Process where shooting the Concrete directly onto the face of the clay sub-strata completely seals the excavation.

Water cannot penetrate down the outside of the pool and cause the clay beneath the pool to swell and lift the pool. Then in summer the clay can dry out and shrink away from the pool so that the structure is unsupported. In the course of 10 years or so this process will wreck the pool structure.



Other Pool Types can be used in Swelling Clays but costly Special Measures are Required

Fibre-glass pools and liner pools can be built in swelling clay areas but great care needs to be taken in the design as with these and every other type of pool water can percolate down into the working space around the pool that is backfilled after the pool has been installed.

The special measures required are costly because they involve the installation of cut-off walls that seal the area beneath the pool base to stop the swelling and shrinking.



Finishes to a Shotcrete Pool

Experts with a Track Record

It goes without saying that the finishes to a Shotcrete pool must be supplied by specialist manufacturers and applied by experts with a track record of successful installations that can be inspected by the Owner-Builder before placing any orders

Tiling

The tiling involves several stages and so it is a quite slow and costly process. There are suppliers that can provide all the products and specifications for your builder to follow.

The concrete shell is never really totally waterproof and so needs a "lining" that normally consists of a cement-based mortar with costly special additives that needs to be trowelled on by skilled plasterers. Alternatively a waterproof coating can be applied to the render.

The lining itself must be left to cure for a period before the tiles can be glued to it – this period can be as short as a few hours when the temperature is 20 degees C or more.

The pool floor will also need to be screeded and waterproofed.

The tiling and grouting will also take a week or so to complete and will then need to be left for period recommended by the manufacturer before the swimming pool can be filled with water.

The grout can be flexible or rigid epoxy type that lasts a lot longer.

The tiles themselves can be of any size – the bigger they are – the more expensive they are to supply and install. Many pools nowadays are finished with mosaic tiles that comes in a sheet that is glued to the render and then grouted.

Coloured Render Finish

There are also different types of render finish available for swimming pools that just rely on coloured mortar with different types of surface finish and many have various types of pebble of quartz finish.

There are specialists that provide skilled installation teams who brush on a bonding coat before applying a special render finish, then trowel up the surface ready for the final job of wet polishing/spinning the finish.

Clients can incorporate a tile band and definition line within the pool or the render can be applied throughout, up to the edge tiles.

Renders comes in a variety of colours including blue, white, yellow, black and jade green.

Renovation of old concrete swimming pools

If an old concrete pool shall is cracked and moving the best way to renovate the pool is to use Shotcrete

 

pool renovation using Shotcrete

 

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Introducing Bluepools

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Bluepools Designs:

Modern Indoor Pools

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Pools in Basements

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Renovation of Existing Pools

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And Specialises in Large

Spectacular Pools

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