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  • #47241
    Ben Gorman
    Participant

    Here is Question 9, along with my thoughts about how to answer it. I don’t know whether or not I have the correct answer. I would be really interested in your comments.

    Be aware that the online quiz tends to change the order of the answer options.

    **** QUIZ QUESTION ****

    Ground Floor
    Quiz question 9
    Suspended timber ground floors are often problematic, potentially failing due the proximity of their component timber elements to sources of ground moisture. In this example the space below the joists is very shallow and floor joists are decaying at critical load bearing points; where the joist ends bear in the external wall (k) and where they bear over the sleeper walls (j). What are the factors contributing to this situation?
    1. position of damp proof course
    2. Blocked vent (z)
    3. A high water table and a bare earth subfloor
    4. External paving (o) laid at a gradient toward the house
    5. no DPC in the sleeper wall
    6. a good quality but untreated timber was used for the joists
    7. a broken shoe on the downpipe nearby
    8. the plastic sheeting and carpet over the ground floor to cut out draughts

    **** MY THOUGHTS ****

    These all sound plausible. I was not so convinced about 8 but in one of the retrofit examples given in the course the retrofitter was surprised that plastic sheeting had been used and gave the impression this would not be a good idea. I think carpet over the floor would not be a problem though. It’s just the plastic sheeting that would not allow the floor to “breathe”.

    #47397
    Tim Gilbert
    Participant

    Hi Ben,

    Agreed, all of them.

    Tim

    #47406
    Ben Gorman
    Participant

    Thanks Tim.

    I’ve had a further thought. If there were no problems with rot/damp/water ingress, would it be possible to use untreated timber for the joists and not experience any issues?

    Maybe 6 isn’t strictly a contributing factor because if it was the case that all the other issues were resolved then the failings would not occur.

    Is it the case that using treated timber is a secondary preventative measure which “kicks in” only when there is unplanned damp/water ingress in order to preserve the life of the timber until the water ingress/damp issues can be resolved?

    #47408
    Tim Gilbert
    Participant

    Hi Ben,

    That depends on how you define “contributing factor”. As far as I am concerned if all the other factors were the same and the joist were treated, or made of some inert material, then the situation wouldn’t arise, therefore it is a contributing factor.

    Actually treated timber doesn’t have an indefinite life if conditions are aggressive enough.

    Tim

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