Tips for working with lime during Autumn

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Working with Lime at this time of year

The summer weather has been disappointing for builders and DIYers, and autumn might be the same. However, planning and carrying out lime work in autumn is still possible. Just be well-informed, plan, and make sure you have everything ready on time. Many of our suppliers, such as Cornish Lime, Lime Green, and St. Astier, specify that their materials should not be used at 5 °C or lower. Unfortunately, these temperatures are typical during winter in the UK, making work more challenging and riskier. However, there is still time this autumn to complete some external work.
Working with lime in cold and wet conditions can be very problematic. The lower the temperature is, the slower a binder develops strength. For example, a 10-degree drop in temperature reduces the reaction rate by approximately 50%.
The significant problem with using lime in lower temperatures is frost damage. As the temperature drops, the rate at which a lime mortar develops strength decreases, and if the mortar is saturated, it will be more prone to damage and failure.
As water freezes, it expands by around 9% in volume. If a mortar is saturated or very wet, there is no space for this water to expand, and it will push itself apart if it’s not strong enough.

Here is our helpful guide for planning to use lime this Autumn.

Lime pointing in autumn and into winter.

There are two stages: the evaporation stage and the carbonation stage. You must avoid frost during the first stage, but that could take a long time in winter. The problem is that once temperatures drop to 5 degrees, they are likely to stay low, and the uncarbonated lime sits around setting very slowly until spring arrives.

1: Forecast to avoid frost damage

Regularly monitor the forecasts and plan accordingly. If possible, avoid working during periods with a high chance of frost within a 2-week period. Also, consider wind chill and speed. For instance, wind speeds of 18mph can chill a 5°C air temperature to freezing at a surface. Wind chill is often the cause of frost failures, where the air temperature is not significantly low, but the chill pushes the surface below freezing.

Oxfordshire cottage finished with Calbux Quicklime mixed with horse hair by Russet & Sage Heritage Conservation.

How long does lime pointing take to cure?

It depends on the mix; a strong hydraulic lime will set much quicker than a non-hydraulic lime putty. It will also depend on how deep the pointing goes; the deeper layers take longer to carbonate. Full carbonation takes many months.

It's quite possible to work throughout the year, provided you cover the work to keep frost at bay.

2: Use well-designed scaffolding

Carefully planned sheeted scaffolding minimises wind and rain impact on the wall or roof. Overlapping the scaffold's top layer with a sloped waterproof sheet ensures water is directed away from the wall. Lastly, plan to have the scaffold up longer than you would in warmer months, as the lime mortar will require additional time for adequate curing.

3: Use hessian sheeting

The traditional method of lime protection is to use builder's hessian. The hessian fabric is hung in front of the lime, with an air gap, to allow airflow for carbonation while protecting the surface from wind and rain. The hessian material can be sprayed with water to help cool the lime in warmer conditions. In extreme conditions such as heavy frost, it's advisable to use hessian wall covering along with a tarpaulin to protect the lime. Covering all your work with a double layer of hessian is recommended to ensure adequate protection.

Hessian - Lime Mortar Protection

If you are particularly worried, then using Hydraulic lime or additives can help with setting and hardening, and are often used in more extreme conditions.

4: Increase frost resistance
Adding pozzolans

Pozzolans are a budget-friendly way to increase the strength development rate with little impact on the breathability of a mortar. With the correct type and dose, it’s possible to achieve frost resistance after approximately a week.

Brick Dust Pozzolan

Polypropylene Fibres

Horse Hair

PRICE DROP
(price will stay low until Christmas!)

Lime Green Ultra - Insulating Render 10kg

NOW £18.67

Was £ 26.67

Ultra is the warmest lime plaster on the market

Lime Green's Ultra lime plaster base coat is a lightweight, insulating base coat that is five to ten times more thermally efficient than other lime plasters. This makes it the perfect plastering base coat for building renovations, where it adds an additional insulation layer to internal walls and protects against salt damage.

Coverage

1 litre per mm of thickness over 1m2. One bag will cover 1.5m2 at 10mm thick, 1m2 at 15mm thick, and 0.6m2 at 25mm thick.

Finishing Coats

Suitable finishing coats are Lime Green Natural Finish or Lime Green Solo.

Extra Deals

Buy 25 - 49 and get 5% off
Buy 50 - 74 and get 10% off
Buy 75 or above and get 15% off

Lime Green Ultra - Insulating Render 10kg

NEW PRODUCT ALERT!

Hempcrete Binder for Hand Casting

Tried and tested formula made in the UK with British lime for better-than-zero carbon building.

This binder contains 20% recycled content and is designed for hand-placed hempcrete or hemp render.

Used for insulating existing walls or building from new around a timber structure., mixed with hemp shiv, Hempcrete binder makes a warm, breathable and low-carbon mix that can be cast between shutters or sprayed using specialist machines.

It has been specially developed for hemp construction methods.

For Mixing, consumption rates and finishing options, please see our website.

Extra Deals