One of the purposes of walls are to retain or hold earth or water materials to prevent erosion. It should be able to resist the pressure from the materials it is holding. We see it in our gardens and in our yards, adding beauty and style. On this blog, I will talk about how to build retaining walls and how to build it with curve designs.
Retaining walls
There are two types of retaining walls, the revetment walls which holds earth materials and the dam that holds back water. Since, these walls should be made to last, there are 3 specifications that it should meet.
1. Sufficient weight to be able to counter the pressure and weight of the materials it holds.
2. Foundation should be wide enough to provide enough friction against the ground.
3. The wall should be wide enough to resist shearing force at any level.
Retaining walls can be built in two ways, either by half-brick offsets or by battered face or sloped as shown in the pictures below. The tapering design is sufficient because the material (earth or water) held back reduces pressure when it gets closer to the top.
Half-brick offset wall (Pave-Masters)
Battered face or sloped wall (Allan Block)
In order to relieve extra pressure on retaining walls that is built for purposes other than as dams, putting a large granular material and a line of porous pipes behind it and building pipes through the wall to let the water escape would help drain water away as shown in the diagram below.
from Paving Experts
Curved wall
Another way to build a wall is to add a curve. A curve wall design can be constructed using the methods below.
a) Alignment with templates and leader bricks.
Leader bricks are built to serve as a gauge for the next layers of bricks. It should be levelled and plumbed on all sides against the first course. It should also be evenly spaced out all through the full length of the wall.
by Sinead Carr
b) Alignment using plumbing points.
Plumbing points are assigned points on the first course, such as the middle of each brick. These points are followed through the full height of the wall to keep the wall perfectly curved and plumbed. The plumbing points are the only points where we should check if the layers are plumb.
by Sinead Carr
c) Alignment using a trammel.
The pole of the trammel, can be a steel rod, is secured at the striking point and it should be as high as the finished wall. It should also be plumbed and rigid. A thick rubber band is placed at the bottom of the trammel to keep it in place and levelled.
by Sinead Carr
The curved walls are built using straight bricks with wedge-shaped mortar cross joints. Radial bricks are also recommended because it allows the cross joints in between the bricks to have a parallel side rather than be wedged shaped. Moreover, the most suitable bonds for curve walls are the header bond and Flemish bond. Below is an example of a radial stretcher brick.
Curved ramps
Another design we can add to our walls are the curved ramps. Curved ramps are built as a decorative feature or to join a wall with a pillar. There are two variations of curved ramps, convex ramp which curves outwards and the concave ramp which curves inwards.
Convex ramp on a wall (Pinterest)
Concave ramp (Garden Proud)
To perfectly add these curves on a brickwork, a trammel is used when marking the bricks. Trammel is used to set out the curve accurately. It is connected via a nail which is drilled at the striking point at the centre of the circle.
How to build a convex ramp
1. Firstly, the striking point is established. The brickwork is built in a square to ensure that it is plumbed and levelled.
2. The trammel is the secured at the striking point using a nail to allow rotation.
3. A pencil is then held at the other end of the trammel bar the mark the curve is marked on the bricks by rotating the trammel.
4. Once the bricks have been marked out for cutting, they should be numbered, measured and removed from the brickwork. This is if the brickwork is not perfectly levelled, plumbed, in range and the perpends is all at the same size.
5. Next is to built back the cut bricks and then the bricks on edge are built on top of them.
6. The bricks used for capping are V-shaped to accommodate the curve.
7. Measure the top of the curve using a measuring to tape to determine how many capping blocks are needed.
For example:
Length: 1600mm
One brick + joint of 10mm: 75mm
1600 / 75 = 21.3 or 22 bricks
To get the joint measurement, divide the length by the number of bricks.
1600 / 22 = 72.7
The measurement of joints should be 7mm. It is still within the acceptable range of 6-10 mm.
8. Allow for an extra joint by randomly marking 6mm for 7 joints.
How to build a concave ramp
1. First, the ramp is built, and the trammel is fixed for cutting using bricks to hold it in place.
2. After cutting the bricks were cut, fixe the trammel back in place to use as a guide for laying the brick on edge.
3. The capping bricks are placed using the trammel as guide.
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