1. Backgrounds and Plaster
Prepare Background Surfaces and Plaster Materials

2. Backgrounds and Plaster
Understand the range of Plasters and the Backgrounds they are used on. 2

3. Backgrounds and Plaster
Aims and Objectives
Aims: To match plaster to a suitable background Objectives: To recognise different plasters suitability to backgrounds 3

4. Backgrounds and Plaster
Introduction
What do you know: What backing plaster is suitable for high suction backgrounds? What backing plaster is suitable for low suction backgrounds? How do we judge the properties of a background? How many backing coat plasters can you name? How do we finish backing coats ?
Work in groups or as individuals
Set a time limit for the questions 4

5. Aerated Concrete Block (Aircrete)
Backgrounds and Plaster
Aerated Concrete Block (Aircrete)
Suitable For:
General build walls.
Likely locations
Cavity walls
Solid walls
Partitions & separating walls
Key: Good mechanical key (very good if scratched).
Suction: High to very high.
Points for Discussion:
The aim of the following slides is to get the students to grasp the relationship between key, suction and plaster. Buy discussing the properties of the background and needs of the background in relation to the properties and needs of the backing plasters a pattern should soon form, avoid showing the students British Gypsums plaster guide initially, give them the basic information needed in relation to each backing coat. Try get them to take the lead. 5

6. Common bricks / Facing Bricks
Backgrounds and Plaster
Common bricks / Facing Bricks
Suitable For:
Exterior walls & facings of buildings.
Likely locations
External walls (aesthetic reasons).
Internal walls (in older buildings).
Key: Good to medium.
Suction: High.

7. Medium Density Blocks Suitable For: General build & residential walls.
Backgrounds and Plaster
Medium Density Blocks
Suitable For:
General build & residential walls.
Majority of standard applications.
Block and beam flooring.
Likely locations
Inner leaf of cavity walls when used with secondary insulation.
Separating or partition walls.
Infill blocks in beam and block flooring systems.
External walls (rendered or clad).
Key: Good to very good.
Suction: Medium to High.

8. Cast in situ & pre-cast concrete:
Backgrounds and Plaster
Cast in situ & pre-cast concrete:
Likely locations
Commercial sector
High rise
Precast stairs and lift shafts
Soffits
Key: Typically poor, but can vary
Suction: Medium to low.

9. Plasterboard & Glasroc F Multiboard
Backgrounds and Plaster
Plasterboard & Glasroc F Multiboard
Suitable For:
Internal wall lining / Ceilings
Curved wall / Ceilings
Key: Medium to low.
Suction: Medium to low.

10. Painted & tiled surfaces
Backgrounds and Plaster
Painted & tiled surfaces
Likely locations Bathrooms, Kitchens, etc… Key: No mechanical key. No chemical key. Suction: Very limited (painted) to zero (tiles)

11. Engineering bricks: Suitable for:
Backgrounds and Plaster
Engineering bricks:
Suitable for:
Denser and stronger than ordinary facing bricks
Two classifications, Class A & B
based on minimum compressive strength and maximum water absorption:
Class B – Red in colour. Smooth in texture. Account for the majority of the market. Among the cheapest bricks in the construction industry.
Class A – Blue/grey in colour. Smooth in texture. Increasingly being used for facing due to their colour, quality and distinctive appearance.

12. Engineering bricks cont
Backgrounds and Plaster
Engineering bricks cont
Likely locations
Where strength and low levels of water absorption are paramount
Retaining walls
Ground works.
Key: Medium (if joints are raked) to poor
Suction: Low to Medium.

13. Dense Blocks Suitable for:
Backgrounds and Plaster
Dense Blocks
Suitable for:
Dense concrete blocks that can be used in virtually any part of the project in normal conditions.
Characteristics
Excellent sound insulation
High strength makes them especially applicable to partition and separating walls.
Block and beam flooring

14. Dense Blocks cont Likely locations Partition and separating walls.
Backgrounds and Plaster
Dense Blocks cont
Likely locations
Partition and separating walls.
External cavity or solid walls
Load bearing & non-load bearing walls
Foundation walls below DPC
Fire resistant walls
Key: Good to medium.
Suction: Medium to High

15. Metal lathing Introduction
Backgrounds and Plaster
Metal lathing
Introduction
Used to provide a mechanical key to a substrate.
Suitable For:
Non-consolidated backgrounds (dusty).
Variable backgrounds (on the same wall).
Smooth.
To provide intricate detailing.
Likely locations
Bridging gaps in walls
Bridging columns
To aid extreme thickness backing coats on very uneven walls.
Key: Good mechanical key. No chemical key
Suction: Zero

16. Conclusion You now should have the knowledge to complete the following
Backgrounds and Plaster
Conclusion
You now should have the knowledge to complete the following
What backing plaster is suitable for high suction backgrounds?
What backing plaster is suitable for low suction backgrounds?
How do we judge the properties of a background?
How many backing coat plasters can you name?
How do we finish backing coats?
Work in groups or as individuals
Set a time limit for the questions 16