WAJD Learning

On site trade skills · Beginner to competent DIY

Plastering: read the wall first

Suction, backgrounds and bonding, because almost every plastering failure is a background failure.

  • 2modules
  • 2.5CPD hours
  • 85guided minutes
  • Freealways

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About this course

Plastering is taught as a trowel skill and fails as a materials decision. A perfect finish on the wrong background still comes off the wall.

This course teaches how to read a background for suction, strength and stability, how to choose the right preparation and plaster for it, and how to diagnose the four common failures from what they look like.

It covers the two health risks the trade has historically shrugged at: respirable crystalline silica, and the alkaline burns that cement causes slowly and often painlessly.

What you will be able to do

  • Assess a background for suction, strength and stability
  • Choose the correct preparation and plaster for that background
  • Explain why gypsum on lime damages a solid wall
  • Diagnose blowing, crazing, joint cracking and delamination
  • Control silica dust and prevent cement burns

Modules

  1. 1 Backgrounds and suction: why the wall decides the outcome 40 min study · 3 min script · 4 question knowledge check
  2. 2 Mixing, laying on and the timing of the trowel 45 min study · 3 min script · 4 question knowledge check

Assessment and certificate

A knowledge check and a final assessment at 80 per cent, unlimited attempts.

A free digital certificate with a verification code. Knowledge only, not a trade qualification.

Questions

Can I just PVA everything before plastering?

No. On a high suction background diluted PVA helps control suction. On a smooth non porous background it leaves a film with almost no mechanical key, and the plaster will eventually blow. Smooth backgrounds need a slurry bonding primer containing aggregate.

My Victorian house has lime plaster. Can I skim over it with gypsum?

You should not. Hard gypsum over soft lime in a solid walled building traps moisture in a wall designed to breathe, and causes the same damage as hard cement pointing on soft brick. Use lime.