General Guidance HSP Masonry

This information should be read in conjunction with the specification.

General
For surface preparation, ensure all surfaces are sound, clean, dry and free from dirt, salts, grease and all other loose material and/or contamination. Wash down previously painted surfaces with a detergent solution to remove all dirt, grease or chalking paint where practicable. Also, treat any areas affected by mould, lichens, algae and moss with Valtti cleaning agent. Rinse off with clean water and allow drying time. Particular attention should be paid to any surface moisture (new surfaces in particular must be fully dry). Special precautions should be taken during surface preparation of pre-1960’s paint surfaces over wood and metal as they may contain harmful lead. All surfaces to be painted must be bonded to the substrates and any glassy or glossy concrete surfaces should be mechanically abraded. Failure to provide an adequately prepared surface may result in poor results and potential flaking or pealing if painting over weak paint layers.

Surfaces
Consideration should always be given to the condition and surface type when decorating and renovating exterior masonry substrates. Ensure all preparation is done before painting.

Renders:
Cement – If not painted before, any loose material on the substrate should be primed with stabilising solution before applying paint. Then, if exterior wall is in a good condition, apply masonry paint. Mineral based exterior paint (Beeck) is also suitable for a more durable finish. Consult a specialist if you believe an inappropriate cement render has been used on an old building.

Silicone – (Polymer coloured render)

Lime – Exterior masonry paint is not suitable.

Pebbledash/Spardash – Repair work of pebbledash or spar dash will not match up, it is also inadvisable to apply render over the top of pebbledash. To paint, ensure all repairs are fixed, such as cracks. For application of masonry paint, use a long pile roller or spray gun. On pebbledash, we recommend using Paracem masonry paint. For Edwardian Pebbledash contact skilled conservators.

Stone:
Brick, Block and Masonry
– Sound preparation will ensure longer durability when painting over brickwork. Ensure the substrate is clean, dry and surface imperfections are correctly filled. Be wary of damp masonry as this will increase chances of problems with efflorescence. If a wall has issues with mould, treat with fungicide wash or a mould resistant primer. Proceed with painting the application of masonry paint.

Note: Fletton Bricks are highly porous and will need to be properly primed to prevent future cracking and peeling of masonry paint.

Condition:
Smooth –
Uneven – Ensure all imperfections are correctly filled and the substrate is free from all loose material and surface contamination.
Unsound – alkaline, powdery or porous surfaces should be primed using
______________and allowed to fully dry. Proceed then with exterior masonry paint.
Damp – Ensure all exterior substrates are completely dry before applying paint as damp substrates will result in flaking or pealing of paint.

Panels and boards:
Ensure all surfaces are clean, dry, solid and free from efflorescence. Before application, touch up open spaces and flaws. Prime with bonding coat before applying topcoat.
Insulation –
Building boards (vermiculite) -


Fillers
Before painting, correct any minor surface defects with Prestonette exterior quick dry filler or the Prestonette waterproof masonry filler. Use a sand and cement mix for larger holes or cracks. Allow to dry. Surfaces that remain powdery, friable or chalky after thorough preparation should be sealed with a coat of Hydrosol Penetrating Masonry Primer.

Brush, Roller and Spray Application
Do not apply in extremes of temperatures (Below 5˚) or during rain, fog or relative humidity above 80%.
The spreading rate of these products will vary considerably according to the roughness and porosity of the surface.
Spray recommendations: satisfactory through most equipment

Weather Conditions
Do not apply in extremes of temperatures (Below 5˚) or during rain, fog or relative humidity above 80%.
The spreading rate of these products will vary considerably according to the roughness and porosity of the surface.
Spray recommendations: satisfactory through most equipment

Personal Protection
Treatments for the removal of surface coatings and repaired surfaces may generate hazardous dust. Work in well ventilated areas. Use suitable personal protective equipment (respiratory, eye and skin), as necessary. Manufacturer’s advice should be followed at all times.

Application
The final overall appearance of the finish is dependent on a number of factors, including colour, absorbency and texture of the substrate, as well as the shade and type of coating used. We therefore strongly recommend that a trial application is undertaken before work is carried out, to confirm its acceptability.


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