PHASE 6 REVISION ANSWERS
1. Sulphate attack in mortar occurs when the soluble sulfate salts within some clay
bricks react with a constituent (tricalcium aluminate) of the portland cement within
2. (a)60 degree method
(b) site formula method (half the span x half the span + rise ÷ rise
(c) geometric setting out
3. (a) A smaller site area is required
(b) Symmetrical section has a similar resistance to bending in both directions
(c) The cavity is wide enough to accommodate services
(d) Less vertical plumbing lines are required so the labour cost of the wall tends to
4. To reduce the power voltage from 230 to 110 V
5. The reason Rat Trap bond is used is it allows a brick wall to be reinforced internally
while the facade of the wall remains untouched
6. The purpose of having a Camber in a Camber arch is to counteract the visual effect of the
arch sagging. It is calculated by using a rise of 1mm for every 100mm of Span.
7. Building the Invert of a Bulls-Eye
A 100 x 75mm timber strut is fixed temporarily on the brickwork either side of the arch
spanning the opening.
The striking point or centre of the bulls eye is then marked on the strut.
It is essential the strut is well stabilised over the opening
This ensures it is not going to move during the construction of the invert arch.
The trammel is usually cut from 44mm x 18mm timber.
The distance between the striking point and the tip or point of the trammel is the outer
radius of the bulls eye plus a 10mm mortar joint
The trammel is then nailed to the striking point marked on the timber strut and should
It is essential to keep the surrounding brickwork accurately ranged and plumb on the
This assists with ensuring the entire circumference of the bulls eye will align with the
The invert is carefully cut to the required semi circular shape.
Each brick is temporarily placed in position using wood spacers or a box rule to
represent bed and cross joints.
The curve is marked with a pencil held at the point of the trammel.
The bricks (creepers) must then be perfectly cut to the required shape.
When the creepers have been cut precisely to the mark they are then set into the wall
It is essential to once again check for accuracy with the trammel.
This process is repeated for each creeper until the invert has been completed.
8. 3.14 x (910 + 215 + 215) 1340 = 4208 ÷ 70 = 60 Voussoirs
9. To calculate this sum do the following........
One tile = .150 x .150 = .0225
Wall = 5.3 x 2.4 = 12.72
Divide 12.72 by .0225 = 566 Tiles excluding waste
566 x 110% = 623 Tiles including waste
10. Setting out tiles
When tiling a wall a level base must be established.
If the tiling begins at some point over floor level - a level base for the tiles to sit onto can
be easily created using a timber gauge batten that is fixed to the wall and correctly
If the tiles begin at floor level its quite likely the floor is not perfectly level
So in this case establish the lowest point of the floor
Measure and mark the wall, one full tile height plus two grout joint widths up from this
Marking one full tile height plus two grout joint from the floor
Using a spirit level to make sure it's perfectly level – nail the temporary gauge batten to
the wall with the top edge corresponding to the mark.
This is the setting out or starting line.
If it is required to finish at an exact height on the wall, in order to accommodate a border
or shower height for example - work down the wall in multiples of the tile size plus joints.
This gives the required level of the starting batten.
Mark the centre of the wall on the batten and centering the first tile, set out a line of tiles
to establish how they fit.
Mark the final position (gauge) of each tile on the batten
Using a plumb line or level create a vertical line on the wall – this should be created at
the last full tile before the corner of the wall to be tiled
11. Unglazed Tiles must have 2-3 coats of protective oil (linceed or manufacturers
recommendations) applied when completely dry. They should then be coated with 2 2-3
layers of lacquer or glazing coat befor grouting takes place.
12. Pocket Reinforcement
This reinforcement is contained in the rear of the wall.
Pockets are left at the back of the brickwork to allow vertical sections of concrete to be
poured around steel.
This type of reinforcing is normally used in retaining walls
13. Backdrop manholes (sometimes called cascade manholes) are used where one drain or
sewer is to connect with another drain or sewer that is at a considerably lower level.
The external backdrop is preferred as the internal causes obstruction when accessing the
manhole – many local authorities will forbid internal backdrops for this reason
14. The workings of a septic tank can be seen in the following sketch
15. Pre stressed Concrete lintels advantages over cast in situ include.
Arrive to site ready made
They are generally slimline
Usually easy to position by 1 or 2 people
No delay in the work process
Cheap and cost effective
Guarenteed strength quality
Can often accomodate greater loads
16. Cavity Wall Lintel for blockwork & Timber Frame construction
17. Common Site Drawings include............
Block plans 1:1250 or 1:2500
Site plans 1:500
General location drawings 1:50 or 1:100
Component drawings 1:100 / 1:50 / 1:20
Detail drawings 1:10 / 1:5 / 1:1
Assembly drawings 1:20 / 1:10 / 1:5 or sometimes enlarged using scales such as 5:1 or
18. Reconstituted stone (also known as engineered stone) is a mixture of concrete and ground
up natural stone that is combined with highly specialised polyester resin
It is then cast into different shapes.
Locations can include, Coin Stones. Window Cills, Lintels, Cappings, Mullion Posts, Paving etc.
19. Three ramps are......
They are used to reduce or increase the height of a wall or simply as a decorative feature.
20. Drawing symbols for materials can be seen below.....