Strengthening floor for bath & HW cylinder

Discussion in 'Engineers' Talk' started by dt99jay, Nov 10, 2022.

  1. dt99jay

    dt99jay Member

    Hi – grateful for any help with this. I'm thinking of turning a first floor bedroom in a 1910 house into a bathroom. The room is rectangular, with load bearing walls on three sides and 2x9" joists running lengthwise at 10-12" centres. Local BC told me I might have to strengthen the floor for the bath (250kg-ish?) but haven't yet specified how (or alternatively said I could get an SE to certify it'll be ok). Since the BC visit I've decided I'll also need to situate an unvented cylinder (300kg) in this room, not sure where but it could be aligned over the same joists as the bath, so I'm kind of resigned to strengthening the floor. Think these are my main questions, would love to hear any thoughts in response:
    1. What are the options for strengthening the floor e.g. additional 5m joists, sister timbers to the existing ones, or might adding noggins be sufficient?
    2. If new joists, should these be pocketed into the load bearing walls or in hangers?
    3. If sistering, can this be done just under the bath and cylinder?
    4. Might I get away without floor strengthening (or with sistering instead of additional joists) floor if bath and cylinder are resting on parallel rather than the same joists?
    5. The ceiling below the room is in fairly good condition but is the original lath and plaster, is there a way to strengthen the floor that avoids damaging the ceiling too much?
  2. Greentram

    Greentram Member

    What's the span of these joists? Generally all floor joists are the same size (or the floors and ceilings wouldn't line up) so need to be sized by the longest span, usually over/under the lounge and main bedroom. If (say) your bathroom joists are spanning 2.4-2.7m over a kitchen, they'll have a massive reserve of strength. Local engineer should be able to check it out for you for a modest charge, especially if you've got a few loose boards so he/she can instantly see everything.
    dt99jay likes this.
  3. dt99jay

    dt99jay Member

    Thanks! Forgot to say, it’s a 5m span.

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