Hessian

Hessian lime protection rolls used following the application of lime mortars, renders or washes, is important to protect the surface while the lime cures (carbonates). Wind and Sun can dry the lime too quickly. Rain will erode the surface and extend the carbonation process and frost will damage the structure of the mortar.

Builder’s hessian is the traditional method of lime protection. Hung in front of the lime, usually with an air gap, the open weave of the hessian fabric allows the necessary air flow needed for carbonation, whilst protecting the surface from wind and rain. In warmer conditions, the hessian material can be sprayed with water to aid cooling. For extreme conditions such as heavy frost, it is advisable to use the hessian wall covering in conjunction with a tarpaulin to protect the lime.

Hessians are categorised by their weight, expressed as ‘gsm’ or grammes Per Square Metre with the lower number representing a more open weave to the fabric with less material used, hence it being lighter.

Roundtower supply 3 grades of hessian:

229gsm – Summer Work: Thin material, won’t offer much protection from adverse weather but is suitable for keeping mortar damp when working in hot periods.

273gsm – All Around: Medium weight material, suitable for most applications.

366gsm – Winter Work: Thick material, offers excellent protection from frosts and adverse weather in the winter months.

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