Harling is a rough-cast wall finish consisting of lime and aggregate, notable for its rough texture. Many castles and other buildings in Scotland and Ulster have walls finished with harling.

What is the purpose of Harling?

Harling (or roughcasting) was originally applied to rough stone walls to protect them from the Scottish weather. It consisted of lime mortar mixed with small stones or shells being hurled or cast against the wall and produced a rough textured finish. Lime wash would be applied every few years to help seal small cracks.

What is a Harling coat?

The lime coating known as harling or wet dash is the most commonly applied external finish to be found on vernacular architecture in Ireland. The harling material is a combination of AGGREGATES and LIME, mixed into a slurry consistency and applied in a fluid state.

How is Roughcast applied?

Roughcast can be machine-applied but hand-casting is as quick for an average-sized house. One method is to throw the mix ‘backhand’ from a casting (‘dashing’) float or cut-down coal shovel. The texture can be modified by wet or dry brushing as the surface firms up. Allow for weather protection.

What is the mix for wet dashing?

The standard mix for wet dash render is 2-3 parts sand, 1 part cement, and 1 part small gravel mix. These are all mixed together to make the rendering mix.

Is Harling the same as rendering?

While this render is still wet a specially shaped trowel is used to throw the pebbles onto the lime surface, which are then lightly pressed into it. Harl, being mostly lime render, cures chemically rather than simply drying. It is also less permeable to moisture and water vapour.

Can you paint over Harling?

Yes, luckily you can paint over pebbledash! Paint on pebbledash works in exactly the same way as paint on smooth surfaces, in the fact that if moisture can get behind the surface it will peel & flake.

What is lime Harling?

Lime harling is a thrown, or cast-on, finish consisting of a slaked lime and coarse aggregate mortar, and it usually has a rough-textured surface. It is the most common type of traditional surface finish found in Scotland on masonry buildings of solid wall construction.

What is lime putty made from?

It is made by slaking the lime with a slight excess of water. When matured (lime putty continues to mature for months), the result is the purest form of non-hydraulic lime, ideal for making fine plasterwork and limewash, but also widely used for pointing masonry and making render, daub and other lime-based mortars.

Is roughcast breathable?

They are often criticised for being unsightly and non-breathable, as well as for failing to take account of the individual historic fabric of buildings.

Is roughcast waterproof?

Roughcast isn’t as breathable as the coating used during a wall refurbishment. This means that roughcast can cause problems with damp over time, as it will affect moisture circulation and evaporation from inside the property. Wall refurbishment coatings are highly breathable, yet waterproof.

How do you roughcast a wall?

A standard mix for the roughcast would be 1 part cement to 2-3 part sand mixed with clean water. The stone or aggregate as it is known is then put into the mix. This is usually a 4-5 part aggregate to add to the above mix.

What sand do you use for pebble dashing?

The correct method for pebbledashing is 3.5 to 1. ( 3.5 plastering sand to 1.0 cement ) for the first coat(scratch coat)including feb/addmix and waterproofer. The waterproofer helps control suction.

What is a Tyrolean gun?

Tyrolean is a sprayed and often coloured mortar or cement mix, which is hand applied with a tool known as a tyrolean gun, or in some cases, a top fed hopper gun powered by a compressor.

What is pebbledash render?

Pebbledash is a form of render used for the external walls of a building in which the top coat is textured by pebbles and stone fragments to create a rough finish. The wall surface is plastered with render and the pebbledash material thrown and pressed in while still wet.

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