Roof Timber Mould

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How to treat roof timber mould


Generally, water leaks and poor ventilation, leading to Condensation, are the main roof defects which give rise to a variety of fungi, moulds and insect attacks. Re-roofing with lining (lining papers, 'sarking', roofing felt) can cause severe mold growth and rot due to reduced ventilation.

Excessive ceiling insulation, pushed down into the roof edges, can also cause Condensation and Mold Growth, because it frequently blocks off the eaves or soffit ventilation.

Heavy Insulation on the ceiling also reduces the amount of warmth reaching the roof space, so that the point at which Condensation forms is reached earlier in cold weather, particularly at night.

Most buildings were designed for minimal or no ceiling Insulation, so do not have sufficient ventilation to cope with additional Insulation, as recommended by Government experts. Additional vents can be fitted, but care is needed to find a working balance, or the Mould may become worse.

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Mould - white, blue or black spots on timber, lining felt, masonry: indicates condensation - increase ventilation, (add soffit or ridge vents), apply Mould Cleaner, treat with Boracol 10RH.

Mould growth on a roof timberExtensive mould growing on roof timbers

Typical Roof Mould - damp cold timber, Condensation = Mold Growth

Mould growing on a rafterMould growing on a plywood roof lining panel

Note the roofing felt - many old roofs are upgraded by installing roof lining felt - this

causes a huge reduction in ventilation - Condensation - then mold growth.

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Monitoring Roof Conditions

    1. First kill the Mould, otherwise you will not be able to tell if your improvements are working - apply Mould Cleaner and when dry treat with Boracol 10RH.
    2. Place a Home Humidity Meter in the roof space and use the Memory and Reset features to record morning and bedtime maximum Humidity and minimum Temperature readings.
    3. Add a little more ventilation - ridge vents, soffit vents or tile/slate vents - and then Monitor the readings again for at least two weeks.
    4. Use our Condensation Test Strips, fixed to a few vulnerable timbers, to check for Condensation
    5. Give our Team a call on 01626 331351 to discuss your results and decide if any further action is necessary.

      Condensation Test Strips - turn blue when Condensation occursHome Humidity Meter for monitoring Relative Humidity and Temperature in the roof.

    Humidity Test Strips - show Condensation in Blue - Meter shows temperature and humidity.

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Use wood preservatives and biocides safely. Always read the label and product information Data Sheet before use.

Wear the correct safety equipment and keep unprotected people and animals out of the treated area for the statutory period given on the label.

All products have some hazards and the COSHH Regulations (Control of Substances Hazardous to Health) apply to ALL building repair and construction products that we sell, even Cement.

If in doubt consult us for free technical help. Take care not to contaminate soil, waterways or the environment with the product or the waste and packaging.

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Newton Abbot, Devon, TQ12 2SN

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