weberpral D

Preparation

Scaffolding must be independently tied to allow for an uninterrupted application. Any faults in the structure, particularly those which may lead to moisture penetration must be rectified.

To avoid dampness and discolouration rendering should be avoided below DPC and within 150mm of ground level. All surfaces must be sound, clean, suitably dry and free of any material which may impair adhesion. The substrate should be suitable for rendering with a designation III mix (1:1:6).

Arrises and feature stops may be formed using clean straight timber battens. Alternatively, suitable beads may be used but, with a scraped finish, these will be evident and must be accepted as a feature.

Please note that scraped renders may, during the scraping process, tend to spall away from the nose of some angle beads. Refer to Weber’s Technical Department for advice on suitable profiles.

Mask as required. Edging tape must be removed before the material has dried.

Expansion joints should be included as required by the substrate and carried through all applied materials.

Do not apply to gypsum plaster or previously painted surfaces.

Mixing

weberpral D should be mixed with 5 - 5½ litres of clean water using either a suitable render spray machine, drill and whisk or tumble mixer. 

To ensure colour consistency, the materials required for complete and adjoining panels should be of the same batch number or be thoroughly mixed together before use.

For best results, use as little water as possible and mix to give a workable consistency.

Note: weberpral D may stiffen on standing. Re-mix product to regain a workable consistency but do not add any more water.

Application

To maintain colour consistency, panels should be completed in sequence around the building.

We recommend that beads are fixed using our dedicated adhesive - weberend bead adhesive.  This sets up to 4 times faster compared to standard mortar options - setting sufficiently within 2 hours (at 20°C) to allow rendering to progress. 

Spray roughcast
Depending on the required finished thickness, a first pass is spray applied to a minimum thickness of 10mm and ruled level. A second texture pass is applied between 1 and 2 hours after the first to form a single monolithic coat with a minimum thickness of 15mm. Total finished thickness should be between 15 and 25mm.

Scraped finish
weberpral D should be applied to the suitable substrate in a one or two-pass operation to a minimum thickness of 18mm, or to a maximum thickness of 28mm. (2 - 3mm will be removed by the scraping process to give a finished thickness of minimum 15mm, maximum 25mm.) It should then be ruled level and allowed to harden for between 5 and 16 hours. Sometimes a longer period may be necessary depending on weather and background conditions.

When weberpral D is green (set but not fully hardened) it should be scraped with a circular action using a scraping tool. It is essential that this is done carefully and evenly, ensuring all laitance is removed and that no part is missed. Thoroughly brush down the surface of the scraped finish using a soft bristle brush.

Dry dash finish

Apply weberpral D by render pump or traditional methods in the usual manner. For 15mm render thickness apply an initial pass to a nominal 10mm, rule level. When sufficiently hard but still green (typically between 1 & 16 hours later depending upon climatic conditions and suction provided by the substrate) apply a secondary butter/dash receiver coat 5 mm in thickness. Please note for a 20mm finished thickness apply a 15mm initial pass, followed by 5mm under the same guidance.

Attempting to dash into a full thickness of render, not applied in layers may lead to slumping and loss of the aggregate into the render.

A flowing edge must be maintained to the render which must not be allowed to skin over before the stone is applied.

On completion aggregate should be lightly tamped into the render with a wood or plastic float to ensure that a good bond is obtained.  All aggregate should be washed and reasonably dry.  The optimum size of aggregate is between 4-8mm.

Ashlar features
Apply weberpral D in two passes to an initial thickness of between 20mm and 28mm to allow for an Ashlar recess from 2mm deep up to a maximum of 10mm. Ensure a minimum of 15mm thickness is maintained at the base of the recess for sheltered to moderate exposure.

Rule level and spatula flat. When the material is still green, scrape the surface as detailed in the guidance notes for scraped finish.

Immediately after scraping, mark out and cut the Ashlar effect using Ashlar tools to produce the desired profile. Thoroughly brush down the surface of the render using a soft bristle brush. weberpral D will set and gain hardness in a similar manner to conventional renders.

Protection from unfavourable weather conditions should always be provided during application and early age curing.

Good Practice

Do not apply:

• If frost is forecast within 24 hours of use
• In damp/wet conditions
• In temperatures below 5°C or above 30°C
• On elevations in direct sunlight or where the substrate is hot

Curing

Curing with a fine spray of clean water may be necessary during rapid drying conditions. 

In hot climates, curing as above is essential for 3-5 days after application.