Backgrounds and Plaster Prepare Background Surfaces and Plaster Materials

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

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

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

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

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.

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.

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.

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.

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)

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.

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.

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

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

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

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