acd setting out curved space

Level 3 Diploma in Plastering

© 2014 City and Guilds of London Institute. All rights reserved. 1 of 19

Setting out to form concave and convex surfaces

PowerPoint Rupresentation

Unit 312: Applying plastering materials to detailed interiors



Assessment criteria5.1 Explain methods of setting out to form concave and convex

surfaces.

5.2 Describe the process of preparing background surfaces.

5.3 Describe methods of applying one, two and three coat plastering.

5.4 Explain methods of fixing beads and trims.

5.6 Evaluate setting, curing and hardening times for plasterwork.



Internal plasteringThis session looks at setting out and applying detailed plastering materials to solid, timber and steel backgrounds:

• Curved concave and convex walls

• Curved ceilings

• Inclined ceilings

• Forming beads

• Forming angles



Concave curved wall with a solid backgroundSetting out semi-circular curved wall• Find the radius of curved

background.• Set gig stick from centre point.• Set out and cut curved rule.• Set out timber dots to base of wall.• Transfer base dots vertically plumb.• Form top and bottom screeds

between dots.• Rule screeds using curved template

rule.• Fill in between screeds and

consolidate.



Completed curved wall



Convex and concaved partitionSteel or timber internal curved walls.

www.essentialbaby.com www.britishgypsum.co.uk



Setting out a curved wall The illustration shows how to set out a segmental curved wall at floor level. A drawn line shows the line of the wall, which is to include a segmental curve in its length.A line needs to be struck between the start of the curve and end to the rise, which determines how far the arch projects.A right angle will then be drawn from these two lines – where they meet and bisect will give you the centre point to set out your radius and form the curved outline.



Curved/barrel ceilingsA similar method is used for setting out curved ceilings.

• Setting out the springing line.

• Forming curved screeds.

• Application and finish.



Premade curved timber barrel ceilings



Inclined ceilings



Preparing solid backgroundsSolid backgrounds that have been built to high standards will probably have to be plastered using a three coat system due to the rectangular shape of masonry being used to build the complex curved surface.

Solid backgrounds can be plastered with modern or traditional plastering materials. However, the method of application will be the same.

Application method:

• Scratch, float and set.

• Benefits between using modern compared to traditional plasters.

• Evaluate curing and setting times of modern and traditional plastering materials.



Preparing timber or steel backgroundsCurved walls and ceilings erected from timber or steel can be prepared by installing plasterboard or EML/rib lath to the background.

Curved walls or ceilings with plasterboard can only be plastered with a lightweight gypsum bonding grade plaster, which adheres to low-suction backgrounds (vermiculite aggregate).

Expanded metal or rib lath can be fixed by nailing, fixed mechanically or tied to the timber or steel joists or stud bearers.

Application of scratch/prick-up coats.

Benefits, labour, costs etc.

Traditional cement-based plasters can be applied to EML and rib lath, which provide a much stronger reinforced surface and also increase fire protection.



Preparing timber lath walls and ceilingsTraditional lime and sand materials mixed with horse or goats’ hair incorporated in the mix would generally be specified for restoration plastering work.

Fibreglass strandsThis process can be time consuming due to the slow set of the plastering material.

When complying to restoration specifications, allowances should be made for increased timespans between each application, scratch coat, float and finish, as these will need to have set and dried before the next coat is applied.

Methods for mixing and application for scratch/prick-up, float and finish.



Plaster beadingAngle beads provide reinforcement and strength in areas that are prone to damage. They have replaced forming angles freehand with timber rules, which was a labour intensive process.

Traditional handheld methods are still practised when producing scratch coats or restoration work where beading is not permitted.

Beads are fixed as part of preparation work before applying the floating or finishing coat and are part of the finished edge or surface.

Beads need to be installed with accuracy and alignment and any bowing or impact damage after installation will reflect in the finished work.

Beads are fixed by bedding in plaster or direct nailing with a tolerance of 3mm in a length of 1.8m.



Angle beads • Fixing procedures

• Handling and storage

www.expamet



Stop beads and special shadow beadsFixing procedure

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Movement beadsPurpose and fixing of movement beads



Hard angles

Angle mould members

The following mould membersreplace a sharp arris:

• Bullnose• Splayed • Sunken • quirked

Bullnose Splayed

Sunken Quirked



Any questions?

acd setting out curved space

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