Lime Skimming Inside: How to Prepare and Finish Internal Walls
Liverpool School of PlasteringLiverpool School of Plastering · Lime guide 3 of 4
An internal lime skim is a fine finishing layer over a suitable backing. It can refresh the appearance of a wall, but it cannot securely bridge loose plaster or replace missing base coats. Start by deciding whether you need a cosmetic finish or a repair.
Choose the finish before preparing the wall
“Lime skim” covers different materials. Mike Wye describes Heritage Lime Plaster as an internal finishing product and gives a 3mm application in two 1.5mm passes. Cornish Lime’s CLM66 is also an internal finish, with a maximum 3mm application. These are named product examples, not a universal thickness or instruction to mix systems. Read the current data for the product you will actually use. [1] [2]
1. Resolve repairs before skimming
Inspect the existing finish and backing. Remove failed material carefully and repair deeper defects with compatible backing material. Prepare a reasonably even surface before bringing out the fine plaster. A hollow, moving or badly deteriorated area needs assessment and repair; applying a fresh skin is not the repair itself. [1]
2. Agree the bond and suction control
Dust, paint and mixed backgrounds make adhesion less predictable. Do not reach automatically for PVA or a standard grit primer: Cornish Lime warns that PVA is generally unsuitable and that film-forming primers can compromise moisture movement on traditional solid walls. A specified mineral primer or lime bonding coat may be appropriate, but the supplier must match it to the surface and intended finish. [3]
Where your system calls for damping, use clean water and work towards even suction. Do not assume a dry patch, painted patch and repaired patch will behave identically. A small trial gives you a chance to judge the preparation before tackling the complete wall.
3. Apply thin, controlled passes
Mix or rework the product exactly as directed. Use a hawk and clean finishing trowel to spread a controlled layer onto the prepared backing. Follow the specified number of passes and total thickness. With Heritage Lime Plaster, the two passes together make the stated 3mm finish; they are not two separate 3mm coats. [1]
4. Finish to suit the material
Bring the surface to the texture required while it remains workable, following the product’s finishing guidance. CLM66 can produce different finishes depending on technique, including floated or smoother surfaces. Let a sample panel establish the result you want. Do not keep adding material to correct deep hollows once you are at the finishing stage. [2]
5. Allow for curing and decoration
Air-lime finishing plaster hardens through carbonation; room conditions affect that process. CLM66’s guidance specifically cautions against use in unheated buildings during colder months. “Indoors” does not automatically mean the conditions are suitable. Plan the work around the product’s temperature and protection requirements. [2]
Choose a compatible, vapour-permeable decoration system and obtain the required waiting period from both plaster and paint suppliers. Looking pale or feeling dry is not, by itself, confirmation that the plaster is ready for every coating. [4]
Before starting your first wall
- Write down the exact product and background.
- Confirm repairs and preparation are complete.
- Have clean tools, measured water and the instructions beside you.
- Wear suitable gloves, eye protection and protective clothing.
- Choose a manageable area and agree the finish on a trial panel.
Can I lime skim plasterboard?
Some named systems allow it with specific preparation. That does not make every lime finish suitable, or turn a boarded wall into a traditional lime wall. Ask for the written board specification before buying materials. [1]
Continue learning
- Lime Rendering Outside: A Beginner’s Guide to Preparation, Coats and Curing
- Lime Plastering Inside: Base Coats for Brick and Stone Walls
- Lime Skimming Outside: Choosing an Exterior Lime Render Finish
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Technical references
Checked 23 September 2026. This introductory guide is not a specification for an individual building. Use the current product instructions and an appropriate project specification.