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Self service exercises in rot repair and treatment

Exercise 1 - Rafters

  • You are standing inside a roof with the following tools: a torch, a tape measure, a 'damp' testing meter, a screwdriver, plus a pad and pencil.

    (Use the attached form to make notes as you go and then compare them with the suggested answers). Click here for a copy of the Form.

    What you can see

    Sloping timbers (common rafters) coming down from the top (ridge) to sit at the bottom on the wall. Are they sitting directly on the wall itself, or on another piece of wood (wall plate)? Which is most typical in your part of the country? Click here to see an example.

    Checking for defects

    You notice that two of the rafters have dark patches in various places and are almost black at the bottom, where they sit on the wall. What other symptoms of decay or attack might you notice? Would these differ at all if the roof was made of a softwood (Pine) or a hardwood (say, Oak)?

    Look for the cause

    What is causing the dark patches?

    How are you going to confirm that the cause is still present?

    Suggest the 'moisture meter' readings on which you might advise a Client as follows: a)no action required, b)at risk, needs treatment

    Give as many examples as possible of where could the cause be coming from?

    How could these causes be eliminated?

    Assess the damage

    How would you decide to what depth the timber is damaged?

    Approximately what proportion of the timber can be damaged and surface repaired, without needing to cut out the section?

    Is damage more important in one part of a rafter than another, from a structural point of view?


    Offer a repair

    In one area there is slight surface damage: when dug out the missing wood measures 2 inches (50mm) x 2 inches (50mm) x 6 inches (150mm). What volume in cc's or litres of repair product will you need and what type of product could you use? Click here to see the product being mixed.

    The bottom 3 foot 3 inches (1 metre) of the 8 inch (200mm) x 2 inch (50mm) rafter is beyond repair. Which timber repair technique could you use to replace it? Click here to see an example.

    Which types of resin products are you likely to use?

    What techniques could be used to cut slots or holes into the remaining timber, for connection to a new piece? Click here to see an example of slots. Click here to see an example of hole drilling.

    How much do you think the repair materials would cost? How long do you think it would take one man to cut out and replace one rafter foot? Click here to see an Estimate and here for a Design.

    What types of treatment could you offer, to minimise the risk of future rot?

    What other measures might you take, depending on the type of roof coverings, to reduce the risk of mould growth and insect attack?

    Some answers

    Click here to see the completed form. Suggest your own improvements to the answers.

    Click here to see examples of this type of repair.

    Click here to see methods of Boron based treatments suitable for this situation.

    Next Exercise - click here


    Course help - David Moore - 01626 872886 -

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