Resilient Flooring to Anhydrite Screeds Incorporating Underfloor Heating Using Norcros Pro Gyp Base
Sometimes referred to as a calcium sulphate, gypsum-based o r flow screed, anhydrite screeds are a mix of fine and coarse aggregates, with a calcium sulphate (gypsum) or calcium sulphate dehydrate binder which are design ed to provide a level surface ready to receive a tiled finish. They have a fluid consistency and can easily be pumped on to sites, meaning that large areas can be laid in a short time and the encapsulation of underfloor heating pipes is improved. Anhydrite screeds experience minimal shrinkage, with a low risk of cracking or curling and can generally be laid thinner than a conventional cement-based screed. They are not suitable for external or wet areas unless a tanking membrane is applied.
N.B. The maximum operating water temperature of anhydrite screeds is 45oC.
1. Allow the screed to dry to a maximum 95%RH, this is usually achieved after 7 days.
2. Lightly sand the surface to remove any laitance or surface contamination.
Mixing stage 1 – Mix parts 1A and 1B of the clear primer together Ensuring that a smooth lump free consistency is achieved.
Application stage 1 – Apply to the screed using the roller provided ensuring that 100% coverage is achieved. Allow to dry(approximately 2hrs) wash roller out after use in clean water and dry.
Mixing stage 2 – Mix parts 2A and 2B of the black primer tog ether Ensuring that a smooth lump free consistency is achieved.
Application stage 2 – Apply to the top of the clear primer using the roller provided ensuring that 100% coverage is achieved. Allow to dry for 24 hrs. Wash roller out after use in clean water and dry. The Primer will dry Grey.
Application stage 3 – Apply 2 coats of the pink moisture suppressant (3) on to the black primer using the roller. Allow to dry between coats
(approximately 1 hour). Apply the second coat at a 90 degree angle to the first c oat to ensure 100% coverage is achieved. Allow to dry
(approximately 1 hour). Wash the roller in clean water after each application.
Application stage 4 – Apply one coat of the yellow gritted primer (4) onto the dry moisture suppressant using the roller and allow to dry.
Application stage 5 – Apply a layer of Norcros 2-Part Levelling Compound and Pro Gyp Base Enhancer.
Pour the contents of the 5 litre container into a mixing bucket and gradually add all the powder whilst stirring with a power whisk fitted in an electric drill un til a smooth creamy lump free consistency is achieved.
The material should be mixed for a minimum of 3 minutes.
Pour the mixed material onto the prepared subfloor and allow to flow to give a smooth finish. Minimal work with a sm oothing trowel is required. The use of a spiked roller will help eliminate trapped air and smooth out trowel/ flo w lines to give a more uniform surface appearance. The mixed material should be applied at a thickness between 2mm to 10mm, but may be taken down to a feathered edge where required. For best results, an overall thickness of at least 2mm should be maintained.
Norcros 2 Part Levelling Compound is self-smoothing, but should any imperfections remain they can be removed by rubbing with a carborundum stone when dry. The underlayment will accept light foot traffic typically 4 hours after application. A 25Kg un it will cover approximately 5 meters square at 3mm of thickness.
Flooring can then be installed as manufacturer’s recommendations.
The underfloor heating may be switched on 14 days after completion, raising the temperature gradually at a rate of 5oC per day.