Quick Fire Guide to installing a raised pond using a fibre glass or preformed pool

RAISED POOLS OR WATER GARDENS: what's so special about raised pools?

In the process of building a raised pool you are creating an instant focal point in an otherwise dull flat, usually formal area. Not only that it also has potential for a seating area or incorporated into raised beds.A dull site.
Children and wheel chairs are less inclined to wander into it and the infirm and disabled have a better view of the contents. Built to the correct height and if it is accessible from all sides, the wheelchair user has no problems maintaining it for themselves throughout the year.
For many Koi carp enthusiasts, the added expense of building up and out of the ground is more than compensated by the ease of maintenance particularly when it comes to maintaining the obligatory filter system

SIMPLE RAISED POOL USING A PREFORMED SHAPE: The Method

Essential tools: Spade, shovel, level, trowel, pegs, lump hammer.
Materials: Sand, cement, 15-20mm chippings (to dust), stone or brick. For capping the edge you might want to use special capping stones, engineering brick, slabs, crazy paving - good for awkward shapes giving a rustic look - or even wood to soften otherwise hard stony formal landscaping.

Site cleared, pool tried in position.1.For a preformed fibreglass or plastic pool - choose your pool shape. A formal shape looks best close to the house, either angular to fit in with the patio shape or round for a wishingFootings in place for the blockwork and, in this case, a small patio. well effect. If it is only partially raised with part set into a bank then any simple shape will do.

2.Place the pool 'in situ'. Level the site beneath where the pool is placed and have it sitting roughly at the level you would wish it to be.

FOOTINGS OR FOUNDATIONS FOR PREFORMED POOLS

3. For the preformed pool option - using a plumb line or a vertical spirit level, mark out the edge of the pool on the ground. Use this as a guide to dig a trench 10cmm/4ins deep for footings all the way round the pool. Take the trench under the pool the same width as the pool rim. It should be as wide as the top of the pool is designed to be. If the top of the pool is going to double as a bench for seating then it needs to be 300mm/1ft wide minimum. There is a good argument for excavating the total area underneath the pool and laying a concrete pad to support the whole pool area. If the material of the pool liner is particularly flimsy or the ground is loose soil or ‘made up’ ground, a concrete pad will make the feature a self contained structure whilst serving as a footing for any concrete blocks laid under the marginal shelves. Always remember that water is heavy stuff weighing in at ten pound a gallon, this means that a little 200 gallon pond weighs the best part of a ton when it’s full of water (so roof gardens beware).

If you are incorporating a raised bed, bog garden or filter system then a second separate trench that takes in all these must run round the planned designed area for the feature. This must be wide enough to take the concrete block skeleton and the width of any facing stone. Therefore 300mm/1ft minimum.
4. In the trench, hammer in the pegs level with the foundation for the patio or 30 to 50mm below the lowest point of the surrounding land around the projected pool. The pegs will all be level with each other and serve as a guide to levelling out the concrete for the footings.
5.Mix concrete in a ratio 6 shovels of chippings to dust to 1 cement, or 4 of 15-20mm chippings, 2 sharp sand and 1 cement. Lay it in the trench level with the tops of the pegs. Tamp down with a sturdy length of wood to consolidate it and remove any air pockets.

BLOCKWORK FOR RAISED PREFORMED PONDS

Beginning to lay the blockwork framework.6.Once the concrete has ‘gone off’, lay ‘4inch’ concrete blocks around the shape of the pool coming up under the rim of the pool. These should end up just supporting it when in place sitting on a 15mm-30mm layer of sand.
7.The support can be made more effective by excavating the soil inside the block work construction as far as is necessary, or building up on the top of the block work with bricks or just a fillet of cement.
If you are using a rigid pool liner, which would not be strong enough to support itself when full of water because of its flimsy nature then a concrete block support must be laid underneath the marginal shelf areas. (You are beginning to wish you opted for the ‘hole in the ground’ option, are you not?)
The blocks around the base should be laid with gaps or pipes or drainage holes with in the upright joints every metre to allow for drainage especially where the blocks are defining a raised planted area.
The blocks around underneath the rim of the pool need to be laid with 50mm/2inch gaps between them. You will use these gaps to feed in the backfill of sand as the stone cladding isBlock work for the stream goes into place built up.
8. You can pour in the majority of this backfill as the blocks go up.
9. If you are considering having a fountain in the pond or a waterfall into it then you will need to install the electrical supply through the wall of the poolside before it is too late. Place a length of 20mm tubing or electricity conduit pipe next to the block work near to where electricity supply arrives at the poolside. The cable will run through the conduit up behind the facing of the block work to a junction box set within the facing that links up to connections for the pumps and any transformers for lighting etc.

Proceed to the next phase – FACING THE BLOCKWORK FOR THE RAISED POND

Pool is tried out in position within the block work. Once all the concrete blocks are in place it is time to face all the visible ones with a material that is more in keeping with what you had planned. This can be brick, stone or wood again. The concrete blocks can even be rendered and painted.
Big square timbers (previous to EU rulings – railway sleepers were ideal) laid horizontally were the quickest option for a formal shape. Pinned together well with reed bars (concrete reinforcement bar) running down through them, you could dispense with the block work skeleton apart from underneath the marginal shelves.
Upright timbers would need to be set in a trench of their own in front of the block work. This would need to be tanalised timber set in at least 6in of concrete.

Alternatively, I have seen timbers fixed against blocks with holes drilled as for screws and then held in place with 'hammer fixings'- which are screws hammered into place already in their own ‘rawlplug’.
If the wall around the pool needs to be as narrow as possible then crazy paving laid on a render of a strong mix 3 sand: 1 cement and a good dollop of SBR bonding is effective.
For a brick facing, I would recommend a hard engineering brick that gives a smoothness that is not abrasive to clothing. Specialist brick companies can find just the brick that is suitable and very often in a variety of shapes for the capping.

Stone facing can be laid randomly or coursed like brickwork. The stone can be ‘dressed’, that is cut to more or less formal shapes on at least one face or you can have free stone. The latter is much cheaper but there is more waste depending on what type of stone it is.

RANDOM STONEWALLING TECHNIQUES

The technique of random stonework is to work in your 'minds eye' in courses, working gradually up all along a particular stretch. On a straight flat wall, perhaps for the face of a formal pool, you start with theBeginning to face the block work corners where the best and squarest stones go. These are the quoins.
Next you go onto the base stones. There needs to be a pattern of large stones around the base. (Remember the gaps or pipes for drainage). These provide a link into which all the other stones knit. It is rather like a jigsaw puzzle with no picture. With a little practice you develop an eye for the right stone for the right place.

One old stonemason's rule is that once you have picked up a stone you must never put it down until you've found a place for it. This is easier than looking for a stone for a particular place. If you lose your eye for it, give up and have a cup of tea or better still a draught of cider. Things will go a lot more swimmingly when you come back to it.
A stone should just look as though it fits. If it wants to tip back or it rocks then it can be held in place with a small wedge at the back. Minor adjustments can be made to stones that do not quite fit with a lump hammer, or ideally a stone hammer with a scudgeon bit at one end.
10. The stone should be laid on a bed of mortar approximately 10 to 15mm thick and gently tapped into place until the mortar starts to bulge out. Ensure there is a good solid backing of mortar behind the stone. Large gaps can be filled with loose stone put into the mortar. This helps give it more strength and saves on mortar.
Mortar. The mortar mix is 3:1, Sand: Cement. This is more durable and elastic if 1 shovel full of builder's lime is added to every 6 of sand.
11. When the mortar has been allowed to ‘go off’ for several hours it can be raked out with a blunt trowel and the stone brushed clean with a stiff brush. Or if you were particularly ambitious, you ‘cut away’ with a trowel around the stone to give a raised pointing.
The most suitable technique will probably be one that is in the vernacular for your area. For instance, a particularly rural effect can be achieved if a little extra care is taken with the stones fitting together and making sure that the cement does not show from the front. With a good solid backfill of mortar then a rustic ‘drystone’ effect can be achieved with the strength of a wall laid with mortar.

RECONSTITUTED STONE FACING.

Facing the blockwork and lining the stream with a pvc liner.Using pre-cast or stone effect concrete facings require a certain amount of experience to maintain the clean lines and sharp neat appearance that the products give when well laid.Rockery started and paving for the patio started Using cement colouring of the right hue in the pointing allows for a little bit novice experimenting.
12. If you want a junction box for the electrics, dont forget it to build it in, and dont forget to build in a tube to carry the pump cable. Leave a strong chord or thin wire lying in the tube to help you pull through the pump cable when you install it.
13. As you work towards the top, fill in the remainder of the backfill of sand behind the blocks supporting the preformed pool liner.

Paving laid and the stream started. Coping stones in place.

Rockery started and coping in place.

Rockery, stream, paving and capping complete

EDGING RAISED POOLS

For raised pools, it is generally wise to have some contrasting material as a coping even if it just the colour, unless the contents of the pool provide enough of a focal point to lead the eye in. In this case it's the same.

CONSTRUCTION

Materials – Capping or coping stones, sand, cement, waterproofing powder or liquid, silglaze. If a good firm bonding is essential then use SBR Bonding solution. This will allow you to dispense with the waterproofer, but is quite expensive.
Tools. Shovel, round ended trowel, level, lump hammer and stiff brush.
Lay out all the stones in place before you cement them down. Yes even for crazy paving, especially for crazy paving.
For formal edging. If you plan to edge the pool with very expensive formal paving, it would be best to construct the size of the pool to fit in with the paving. This would minimise stone cutting, which if the stones are precast, always looks slightly untidy. However this may not have been an option and you may have to make the best with the size of pool that you have got. So…
Start laying the slabs from the corners and work to the middle, in this way when you get to the middle and they don’t quite fit, you will only need to cut the middle one (or two). In this way the formal balance is maintained. Cut the slabs with a disc cutter fitted with a stone cutting disc. These can be dangerous, dirty machines and a little daunting for the newcomer who might find it better to mark out the slabs that need cutting and take them down to a local friendly stone merchant. If slab has a chamfered natural edge and there is one slab to cut on each side of the pool, it is best to cut both edges of the slabs to maintain consistency. If two slabs each side need cutting, just cut the inside edge and butt them up together.

For laying informal and formal edging, mix a strong sand/cement mix of 3:1 with the correct amount of waterproofing additive.
Lay the stones in sections at a time. Lay small units on a ‘ribbled’ bed of mortar, whereas larger sections of paving can be laid on spots of 3 or 5 and tamped down to the required level with the handle of the lump hammer. Remember the fall of the stone should be slightly away from the pool.

Be careful not to put too much mortar on the inside edge and try not to tamp the stone down too hard as this will force out the moisture from the mortar and dribble down the inside of the pool.

Do not forget to insert any tubing or conduit to carry power cables.

Pond verging on completion. Plants in place.You may need an overflow at the most practical point away from view below the level of the conduit tubing if you dont want the electricity conduit to act as an overflow or siphon.
Stonework is usually pointed once the slabs are set in place. The best way is to 'hatch' or chop in with the edge of a trowel from the edge of a board a fairly crumbly mix into the gap between slabs. It is like the mix of butter and flower for pastry before you add the water. It sits crumbly in the bucket but will just about smooth out if you trail a trowel through it.
When you have filled a gap with the pointing mix, run the trowel along it to smooth it flush with the paving and to make sure it has properly filled the channel. Scrape the loose excess into the next nearest gap and continue.
Come back a little bit later as the mix is going off to brush or scrape away any further excess. This tends to dry more quickly than the main strip of pointing and just rubs away leaving a neat line of mortar filling the gap.
Treat exposed cement next to the pool with silglaze to neutralize the lime.