10 things you should know about plaster

  1. What thickness are plasters applied? Undercoat plasters are generally applied 11mm thick (for walls), or 8mm (for ceilings) and finish coat plasters at 2mm thick. Thistle Universal OneCoat plaster is applied at 13mm thickness (for walls), or 10mm (for ceilings). ThistlePro Magnetic Plaster is applied at a minimum of 3mm. 
  2. What plaster to apply to sand & cement undercoats? The best finish to apply depends on suction level of the background material. Thistle MultiFinish or ThistlePro DuraFinish would both be suitable.
  3. What plaster to use after DPC installed? Thistle DriCoat is cement based plaster for re-plastering after a damp proof course. Please refer to the plaster section of the White Book for further information if required.
  4. How to plaster an existing painted wall? If the paint is in very good condition in terms of quality, strength and adhesion etc, it may be possible to wire brush the surface using a suitable detergent and apply Thistle Bond-it prior to the application of Thistle MultiFinish. We suggest carrying out this procedure on a trial area to ascertain the suitability.
  5. Where would you use Thistle GypPrime? Thistle GypPrime is a suction control primer used to reduce suction on very dry backgrounds. It is normally diluted (up to 5 parts water to 1 part Thistle GypPrime) or undiluted if severe suction control is required. Plaster is applied after Thistle GypPrime has soaked into the background.
  6. How can plaster assist in reducing air leakage of a building? Using Thistle plasters to plug gaps and cracks is a quick and easy way of maintaining airtightness. Gyproc Soundcoat Plus is used as a parge coat when using a dot and dab method with plasterboard.
  7. Does plastering help increase thermal mass? Thistle plaster is ideal for use where thermal mass is an integral part of the design of a building. Plaster provides the desired decorative finish whilst also enabling efficient heat transfer between the air and fabric of the building.
  8. Can I plaster a damp wall? Not if the wall is subject to rising or penetrating damp. Yes, if there is just residual dampness after successful DPC treatment. The wall needs to treated to eradicate any damp issues such as a damp-proof course. Thistle DriCoat could be used following a successful DPC installation. Please refer to the plaster section of the White Book for further information if required.
  9. How should salt contamination on a background be dealt with? Any salts brought to the surface of the background during drying should be carefully removed. The background must be clean, sound and free from dust. Heavy salt contamination can cause persistent damp problems, so it is important to establish whether the salts are purely from the drying process or whether a more serious damp problem exists. See the White Book for more information.
  10. How much plaster is made in a typical week? Barrow-upon-Soar, the home of Thistle Plasters, produce around 440,000 bags of plaster a week – that’s enough to plaster 29,000 homes.


Frequently Asked Questions

What is the maximum temperature that Thistle plaster can be used at?

For gypsum based products the maximum temperature in normal use is 49oC.

What is the minimum temperature that Thistle plaster can be used at?

We recommend 2°C (5°C for ThistlePro DuraFinish and Thistle DriCoat) as the minimum working temperature in which plaster should be applied. It is important that the temperature does not drop below 0°C during application or in the setting and drying phase.

What is the coverage of a bag of plaster

The coverage varies for different types of plaster. Bag coverage in m2 for individual products can be found in our Plaster selector guide produced in a handy reference chart format. Please refer to White Book Chapter 07 Section 02 Page 03 and Page 04 for further details.

How much water is required per bag of plaster?

The amount of water required differs depending on the type of plaster and ranges between 17.5 litres per 25kg bag to 11.5 litres. See the Plaster selector guide for more details.

Can I plaster an Artex ceiling?

You could consider the use of Artex Easifix Smooth-It or overboard with suitably installed Gyproc plasterboard ceiling system (such as counter battening with timber or by using GypLyner UNIVERSAL). 

Where would you use ThistleBond-it?

ThistleBond-it is usually used in plastering applications where a background requires an improved key.

What is the coverage of ThistleBond-It

The 10 litre tub will cover approximately 45m2 if used undiluted (equates to 4.5m2 per litre). 22 litres would be required to cover 100m2 if used undiluted. Please refer to White Book Chapter 10 Section 06 Page 07 for more details.

What is the coverage of Thistle GypPrime?

The 11 litre tub will cover approx. 100m2 if used undiluted (equates to 9m2 per litre). Please refer to White Book chapter 10 Section 06 Page 07 for more details.

Can you skim an MR grade board?

Yes, however the board usually needs to be primed with Thistle Bond-it. Read the full answer

Do you recommend plastering over sanded lime backgrounds?

No, we would recommend instead drylining using GypLyner UNIVERSAL. Please refer to White Book Chapter 07 Section 04 Page 02 for more details.

Can I paint wet plaster?

Yes as long as the paint is permeable. There should be good ventilation to provide good drying conditions.

Which Robust Detail can I use for plaster?

E-WM-1, E-WM-2, E-WM-18 & E-WM - 21 all deal with dense and lightweight aggregate blockwork with a 2 coat plastered lining.


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