Sands for NHL Mortars – Guide

Choosing the correct sand when making a mortar is of extreme importance. Sands should be clean and uncontaminated by clay/silt. These occur in the range from #300 and below and the most effective method to establish their presence is the wet sieve analysis. Normal dry sieve analysis does not accurately reveal the presence of clay […]

NHL Renders – Guide

NHL Renders General information Sands for renders Background preparation Two coat work Three coat work Protection Good working practices Render Diagnostics Some recommended mixes   Other General Guidelines documents: Render on cob Render on wooden lath Render on metal lath Render on blocks Rendering with a spray gun The correct specification for any render should […]

Pointing with NHL – Guide

Pointing with NHL Understanding mortars Choosing mortars Resistance to salts Protection and working practices Repointing: preparation, application, finishing Repointing dense masonry Repointing ashlar masonry NHL Mortar mixes April 2001       Re-Pointing Masonry Walls: Brick, Blocks and Natural Stone. Understanding mortars. Before deciding to re-point a basic understanding of the function of mortars is […]

NHL Render – Guide

Background Prepare background Re-point and dub out as necessary with compatible mortar. Stipple Coat Cast or sprayed on only Must be used on poor suction, dense / smooth surfaces. Leave as Cast Cure 2 – 4 days First Coat Cast, spray or lay on. Well-keyed background. Control suction. Leave Keyed Cure 4 – 7 days […]

Plaster on Blocks – Guide

External Plastering (Rendering) On Concrete Masonry Units To obtain the highest vapor permeability a block construction should be built with an NHL mortar. Sands: always use well graded coarse sand (#5 to #200) unless indicated. NHL mortar will not alter the color of the sand. See also Sands for NHL Mortar. Main recommendations: make sure that […]

Render on Cob – Guide

Cob is a very simple (and efficient) form of construction that has probably been around forever in some form or other. Structures are formed of earth (normally of a high clay content), with some straw and sufficient water to make the mixture readily workable. The exact ingredients are prone to change along with the many […]

Plastering with a Spraygun – Guide

This method is particularly suitable to ensure optimum bonding even on smooth surfaces. Spraying is recognized as the best method of application allowing sharper sands and lower water content in the mortar mix. The speed of work is considerably increased and an average of 1000 square feet per day per man is quite normal. The […]

Plastering with NHL – Guide

Using St. Astier NHL plastering mortars instead of non hydraulic putty mortars reduces the working time by about 50%.  NHL mortars offer similar vapor exchange qualities as putty mortars but are more robust, can be sprayed and  used for decorative plaster work without the addition of gypsum. Requiring less after care than putty, it can be […]