Sample Garden Pond Design – Building a Raised Pond
A raised pond will require a retaining wall, either to conceal the preformed liner, or to hold the shape of the pond. For the purposes of this article, we will assume that we are using EPDM liner. However, the same steps can be used to build a retaining wall around a preformed pond.
Retaining walls can be built with concrete blocks, brick, or stone. Concrete blocks are more inexpensive, but they are heavy, don't offer much in terms of aesthetics, and are not very adaptable. Stone is expensive, but attractive. Brick is a happy medium between the two because it is affordable, easier to handle, and more adpatable. In order to choose the material that you require, consider the cost, style, and the labour required.
Preliminary Considerations Prior to Building a Retaining Wall
Since the retaining wall will be the part of the pond which most visitors will notice first, to follow are several considerations that need to be taken into account prior to building the retaining wall:
- Decorative vs. Functional walls – functional walls need to be sturdier and hold the weight of the water. Thick walls are more stable than thin ones. It is recommended that functional walls be at least 2 bricks thick.
- Curved wall vs. Straight wall
- How the wall construction material fits in the with existing decor – materials should be chosen which complement the house or nearby garden walls.
- The budget of the job
- Is there easy access to get the materials required (i.e. large stones) into the work area?
Building The Retaining Wall
1. Building the Retaining Wall Footing
Retaining walls require footings for stability reasons- footings provide a stable concrete surface for the construction of brick walls and fences. A footing is usually constructed from concrete that is laid directly on top of a trench full of hardpan. There are three layers that are required for a proper footing:
- LOWEST LAYER- A layer of hardpan (large rocks) to allow for water drainage.
- A layer of sand or finely-crushed rock, in order to allow for adjustments in leveling.
- HIGHEST LAYER- A layer of concrete, on which the retaining wall will be built upon.
To start building the footing, dig a trench that is an approximate depth of 1 foot that is 1 foot wide. Please note that in the Northern US and Canada, this trench may need to be up to 5 feet deep to get below the frostline (otherwise, the freezing and thawing may cause the footing to shift). Place 1/2 foot of compacted hardpan into the trench, followed by 1 inch of compacted soil. Top this off with 5 inches of well-tamped concrete. If the ground is hard and dry, the hardpan layer can be thinner, whereas if the ground is softer, or if the frost line is deep, more hardpan and a deeper layer of concrete may be required.
Concrete mix: A good ratio is 1 part of Portland cement to 2 parts of sharp sand and 3 parts of washed gravel. Once laid down the concrete should be covered to protect it from the elements while curing.
2. Preparing The Mortor
A wall can be built using brick or using stone, but mortar will be required for both applications. Unlike Portland cement, which can be purchased ready-mixed, mortar has to be mixed on-site. You can mix a small amount in a wheelbarrow, a sizeable pile on a workboard, or a larger heap in a cement mixer. A good mortar mix is 1 part Portland cement to 1 part hydrated lime and 6 parts soft sand.
3. Building The Retaining Wall
Brick Retaining Walls
If brick is to be used to build the retaining wall, then keep in mind that bricks have 6 sides: two end "header" faces, two side "stretcher" faces, a top "frog" face and a bottom face. Most walls are built with the bricks set frog-face uppermost, so that the stretcher or header faces are on view. Each row of bricks is called a course, and the pattern of bricks is termed the bond. The object of the bond is to stagger the vertical joints in order to create a strong wall.
The top of the wall should be finished by a coping (e.g. tiles), whose function it is to bring the wall to a visual conclusion and to deflect rain water away from the wall. To follow are the steps that need to be followed in order to lay out a straight brick wall:
 |
Similar instructions apply for a circular retaining wall. To build a circular brick wall, use smaller bricks. The smaller the block, the easier it is to build a circular wall. Use a trammel, which is pivoted on a nail that marks the center of the circle, to ensure that the radius is consistent. Stone Retaining Walls Stone walls are quite similar to brick retaining walls, except that the stones are bedded in mortar. The stone used is usually thin and flat. You may need to cut the stone yourself by using a stonemason's hammer with a brick chisel and/or a cold chisel. |
< Back to Pond Landscaping Guide- Table of Contents
Pond-Building AdvicePond Maintenance |
Business Advice for Landscapers |