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KEY BENEFITS

  • High strength formulation for durable and reliable surface repair.
  • Very low tension, reducing the risk of shrinkage or stress on substrates.
  • Ideal for thin applications, enabling precise patching and fine surface corrections.
  • Effective on multiple substrates.

CHARACTERISTICS

  • Colour: White
  • Composition: Gypsum‑based powder with special additives
  • Coverage: ~1.1 kg/mm/m²
  • Mixing ratio: 8 L water / 20 kg bag
  • Application thickness: 1–10 mm in one layer
  • Application temperature: +15 °C to +25 °C
  • Working time: Approx. 20 minutes
  • Walk‑on time: After 2–3 hours

Screed smoothing compound for surface preparation

As a reliable screed smoothing compound, RENO G905 ALPHA ST is used for repairing, patching and smoothing surface imperfections. It is particularly suited to calcium sulphate screeds, as well as cementitious substrates and existing surfaces requiring preparation before further finishing.

Typical substrates include:

  • Cementitious screeds
  • Calcium sulphate screeds
  • Wooden boards
  • Plasterboards and gypsum fibre boards
  • Existing tiles and painted surfaces

Thin layer repair mortar for precision applications

This thin layer repair mortar is suitable for applications from 1 mm up to 10 mm in a single layer, enabling precise surface correction without excessive build-up.

It is particularly effective for:

  • Smoothing minor surface imperfections
  • Preparing subfloors prior to floor coverings
  • Creating a consistent, level surface

Low slump repair mortar for controlled application

RENO G905 ALPHA ST functions as a low slump repair mortar, allowing controlled application without excessive flow. This supports accurate placement and finishing, particularly on vertical surfaces and detailed areas.

Its formulation also provides:

  • High strength performance
  • Very low tension characteristics
  • Smooth finishing capability

Application process: RENO G905 ALPHA ST

Quick Application Steps (On-Site Guide)

  • Prepare: Ensure substrate is firm, dry, clean and appropriately primed
  • Mix: Add 8 L water to 20 kg bag and mix to a smooth, workable paste
  • Apply: Trowel on between 1–10 mm thickness
  • Wait: Allow light traffic after approximately 2–3 hours
  • Cover: Install finishes after 24–48 hours depending on thickness

1. Subfloor preparation

Proper surface preparation is essential for a consistent finish:

  • Substrates must be dry, stable and free from dust, grease and contaminants
  • Remove weak layers, laitance, coatings and adhesive residues mechanically
  • Thoroughly vacuum all loose debris prior to application
  • Ensure tiles are securely bonded; repair or remove if necessary
  • Smooth or dense substrates should be abraded and cleaned
  • Treat cracks and joints using compatible repair systems before smoothing
  • Apply a suitable primer according to substrate type

All substrates should meet relevant site standards before work begins.

2. Mixing

  • Pour 8 litres of clean, cold water into a mixing container
  • Gradually introduce the powder while mixing with a drill and paddle
  • Mix for approximately 2 minutes until a uniform, lump-free consistency is achieved
  • No resting period is required before use
  • Working time: approximately 20 minutes

Important: Excess water will reduce strength and affect performance.

3. Application

  • Apply in a single layer from 1 mm up to 10 mm thickness
  • Place the material onto the prepared surface and spread evenly with a trowel
  • Press firmly into repairs and imperfections to ensure full contact
  • Level and refine the surface within approximately 20 minutes before stiffening
  • For additional layers, allow sufficient curing before reapplication
  • Suitable for patching, smoothing and preparing surfaces prior to levelling or floor finishes

The low-slump formulation allows controlled application on both floors and vertical surfaces.

4. Drying & curing

  • Working time: ~20 minutes
  • Walk-on time: ~2–3 hours

Protect from rapid drying caused by draughts or direct sunlight.

Typical covering times:

  • Up to 3 mm: ~24 hours
  • 3–5 mm: ~48 hours
  • Additional thickness: allow ~24 hours per mm

5. Underfloor heating

  • Switch off heating systems 48 hours before, during, and for at least 48 hours after application
  • Gradually bring heating back to operating temperature once cured

Common mistakes to avoid

  • Overwatering the mix, reducing strength and finish quality
  • Mixing too much material given the short working time (~20 minutes)
  • Applying onto poorly prepared or contaminated substrates
  • Failing to use the correct primer for the substrate
  • Exceeding maximum thickness in a single application
  • Applying outside recommended temperature range (+15°C to +25°C)
  • Allowing rapid drying due to airflow or direct sunlight

A complete solution for surface smoothing

Combining the performance of a thin layer repair mortar, low slump repair mortar, and skim repair mortar, RENO G905 ALPHA ST provides an effective solution for smoothing, patching and preparing interior wall and floor surfaces prior to final finishes.

Frequently Asked Questions

Minor surface imperfections can be smoothed using patching compounds such as RENO C715 EASY FLASH or RENO G905 ALPHA ST. These are suitable for thin applications, typically from feather edge up to 10 mm, depending on the substrate. Priming may be required depending on substrate type.

Surface imperfections such as minor damage, uneven areas or shallow defects can be repaired before flooring installation using RENO C715 EASY FLASH for patching and smoothing minor surface imperfections, or RENO G905 ALPHA ST for repair, patching and smoothing surface imperfections prior to levelling compounds or floor coverings.

RENO C715 EASY FLASH is a rapid drying patching and smoothing compound for internal repairs on walls and floors, recommended for patching and smoothing minor surface imperfections prior to floor coverings. RENO G905 ALPHA ST is a gypsum based smoothing compound for interior use on walls and floors, recommended for repair, patching and smoothing surface imperfections, with an application thickness of 1 to 10 mm. RENO C715 EASY FLASH is positioned for rapid patching and feather edge work, while RENO G905 ALPHA ST is positioned for smoothing and patching surface imperfections.

Damaged mortar, holes and surface imperfections can be repaired with different products depending on the repair depth and finish required. RENO C715 EASY FLASH is described as a rapid drying patching and smoothing compound for internal repairs on walls and floors. RENO G905 ALPHA ST is recommended for repair, patching and smoothing surface imperfections. RENO C950 QUICK and RENO C920 ST are recommended for deep or large repairs in a single layer.

Application thickness varies by product. RENO C715 EASY FLASH is suitable from feather edge up to 15 mm. RENO G905 ALPHA ST is 1 to 10 mm. RENO C950 QUICK is 1 to 50 mm in one layer. RENO C920 ST is 1 to 50 mm unextended and 50 to 100 mm extended. RENO C970 PLUS is 1 to 100 mm.

Repair mortars are used to restore damaged concrete or masonry surfaces. They provide strength, durability and a smooth finish, and allow professionals to fill cracks, level surfaces and reinforce structures.

Repair mortars can be used for stair repair, shaping slopes, chase filling, crack bridging and concrete repair. They can also be used for filling holes, reprofiling stairs, reshaping slopes and surface levelling, depending on product.

Repair mortars provide strength, durability and a smooth finish. In renovation, they are positioned to restore damaged surfaces and support long-lasting performance.

Repair mortars must be mixed with clean water using the ratios specified per product. RENO C950 QUICK uses 5 to 6 litres of water per 25 kg bag, RENO C920 ST uses 5.5 to 7 litres per 25 kg bag, and RENO G905 ALPHA ST uses 8 litres per 20 kg bag. Mix using an electric drill and paddle until a smooth, lump-free consistency is achieved.

Drying time depends on the product and thickness. RENO C950 QUICK is walkable after 45 minutes, with floor coverings from 1 to 24 hours depending on type. RENO C920 ST is walkable after 30 minutes, with coverings from 1 to 24 hours. RENO G905 ALPHA ST is walkable after 2 to 3 hours, with full curing from 24 hours depending on thickness.

Floor levelling can be achieved after repairing cracks and imperfections. RENO C970 PLUS can be used to level and build up surfaces up to 100 mm, making it suitable for shaping slopes and correcting uneven substrates. For smaller levelling applications, RENO G905 ALPHA ST can be used before applying a levelling compound.

Rough or uneven floor surfaces can be smoothed using patching and smoothing compounds. RENO G905 ALPHA ST is suitable for smoothing surface imperfections with an application thickness of 1 to 10 mm. For minor repairs and smoothing before floor coverings, RENO C715 EASY FLASH can be used from feather edge.

Before installing floor coverings, damaged or uneven substrates can be repaired and smoothed with products selected to suit the defect. RENO G905 ALPHA ST is recommended for repair, patching and smoothing surface imperfections. RENO C715 EASY FLASH is recommended for patching and smoothing minor surface imperfections prior to installation of most floor coverings. RENO C950 QUICK and RENO C970 PLUS are recommended for deeper repairs, levelling, profiling or reshaping where higher build is needed.

Consumption depends on the product and thickness. RENO G905 ALPHA ST uses approximately 1.1 kg per mm per square metre. RENO C950 QUICK and RENO C920 ST use approximately 1.6 kg per mm per square metre. RENO C970 PLUS uses approximately 1.5 kg per mm per square metre.

A damaged subfloor can be repaired using repair mortars and reinforcement systems. RENO G905 ALPHA ST is suitable for patching and levelling imperfections. RENO C950 QUICK or RENO C920 ST can be used to fill holes, reshape surfaces and restore the subfloor. For weak subfloors, RENO U550 REINFORCE helps stabilise and distribute loads.

Walk-on time depends on the product. RENO P520 EASY is walkable after about 30 minutes. RENO C920 ST is walkable after about 30 minutes. RENO C950 QUICK is walkable after about 45 minutes. RENO G905 ALPHA ST is walkable after about 2 to 3 hours.

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