1. Backgrounds and plaster
Prepare background surfaces and plaster materials

2. Understand the range of plasters and the backgrounds they are used on

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

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 coats can you name?
How do we finish backing coats?

5. Backgrounds and plaster
Aerated concrete block (Aircrete)
Suitable for:
General build walls
Likely locations
Cavity walls
Solid walls
Partitions and separating walls
Key: Good mechanical key (very good if scratched)
Suction: High to very high

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

7. Backgrounds and plaster
Medium density bricks
Suitable for:
General build and 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. Backgrounds and plaster
Cast in situ and pre-cast concrete
Likely locations
Commercial sector
High rise
Pre-cast stairs and lift shafts
Soffits
Key: Typically poor but can vary
Suction: Medium to low

9. Backgrounds and plaster
Plasterboard and Glasroc F MULTIBOARD
Suitable for:
Internal wall linings / ceilings
Curved wall / ceilings
Pre-cast stairs and lift shafts
Soffits
Key: Medium to low
Suction: Medium to low

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

11. Backgrounds and plaster
Engineering bricks
Suitable for:
Denser and stronger than ordinary facing bricks
Two classifications, Class A and 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. Backgrounds and plaster
Engineering bricks
Likely locations
Where strength and low levels of water absorption are paramount
Retaining walls
Groundworks
Key: Medium (if joints are raked) to poor
Suction: Low to medium

13. 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. Backgrounds and plaster
Dense blocks
Likely locations
Partition and separating walls
External cavity or solid walls
Load bearing and non-load bearing walls
Foundation walls below DPC
Fire resistant walls
Key: Good to medium
Suction: Medium to high

15. 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

16. Backgrounds and plaster
Metal lathing
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

17. Backgrounds and plaster
Composite rounds
These backgrounds containing different materials are often a source of cracking or loss of adhesion.
Concrete or timber lintels over doorways and windows can cause trouble unless treated.
A composite background can be made up of any of the bricks and blocks covered in the slides.

18. Backgrounds and plaster
Conclusion
You should now 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?

19. THANK YOU