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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorlsx
    • CommentTimeAug 20th 2019 edited
     
    Hi

    I'm a long time lurker, but really appreciated the advice I got on my last post, so thought I'd try my luck again.

    I'm slowly renovating a late 19th century victorian terrace in 'uddersfield. I've uncovered a situation with the joists where previous tradesmen have run riot with probably only an old lady to keep on them:(

    The joists are 7" x 3" on 400mm centres, span 4 metres in most cases but sometimes 4.4m. What I've found is that there are 32mm holes outside of the .25 - 0.4 of span zone like 300mm from the bearings in lots of places.

    While I'm renovating I actually have fairly good access to the underside of the joists, so the time to do something about it is now. I'd like to do something about it myself if poss.

    I imagine a proper fix is to sister any joists that are bad enough. Random googling though has brought up people glueing+screwing 18mm WBP ply to the sides of the joists to support the damaged area. Has anyone got an experience of doing this? Is this seen as a poor man's version of sistering or appropriate sometimes?

    Any advice appreciated.

    :thumbup:
      IMG_0031.JPG
    • CommentAuthortony
    • CommentTimeAug 20th 2019
     
    Don’t worry about it. Probably better to use them again rather than trying to repairing them and drilling other holes.
    • CommentAuthorCerisy
    • CommentTimeAug 21st 2019
     
    Agree with Tony - at those centres not much of an issue. Also - probably one of Tony's previous pieces of excellent advice - nail not screw.
    • CommentAuthorCWatters
    • CommentTimeAug 21st 2019
     
    +1 They seem to be reasonably centered vertically. Notches or holes near the top/bottom would be more serious.

    I don't think adding ply would make much difference as half the grain is in the wrong direction. I think angle iron or metal straps either side below the hole would be more effective.

    http://www.miteknz.co.nz/Products/LUMBERLOK-Timber-Connectors/Subfloor-And-Slab-Fixings/Floor-Joist-Stiffener/
    • CommentAuthorjfb
    • CommentTimeAug 21st 2019
     
    Why nail not screw if you were to do something like this? Strength?
    •  
      CommentAuthordjh
    • CommentTimeAug 21st 2019
     
    Posted By: jfbWhy nail not screw if you were to do something like this? Strength?

    Nails are rated for shear. Screws are not, with the exception of things like coach screws.
    • CommentAuthorGreenPaddy
    • CommentTimeAug 22nd 2019
     
    Not sure there's a huge problem with these as 7x3 at 400 cntrs is pretty robust. However, if you feel you'd like to do something, at low cost, and not particularly labour intensive, you could do the following, which is a method I use for site-build of smaller roof trusses, and will certainly add strength...

    - 18mm plywood, cut in 175x600mm strips
    - PU glue one to each side of each joist
    - nail them with 50x3mm galv round head nails (glue's prob going to do most of the holding anyway)
    - say 20 nails each side, approx 30mm in from the edges.

    Prob £30 for sheet of ply, £10 for nails and glue.
    • CommentAuthorMike1
    • CommentTimeAug 25th 2019 edited
     
    Provided they're close to the centreline, then I'd not worry about them either, unless the floor is flexing unduly.

    If you do decide to fit ply, then nailing is the way to go, but use 40mm sheradised square twist nails. They're designed for heavy duty applications - fixing joist hangers and the like (though normally in 30mm for metal-to-timber connections) - and are very resistant to being pulled out.
    • CommentAuthortony
    • CommentTimeAug 25th 2019
     
    I would say centres between centreline and 2/3 of the way up would be ok.

    Do nothing is still my recommendation
  1.  
    I'm blocking holes like that in our place, as I found they allow draughts and mice to move at will around the place and pop up where they are least wanted.

    The section requirements for timbers are set out to prevent them flexing too much. If you are happy with the bounciness or otherwise of the floor, then don't worry, it's doing its job. It will flex a long way before it breaks.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 27th 2019
     
    And feels more 'friendly' and relaxing - old fashioned even. I hate rock-hard solid floors esp on upper floors (but no objection to a tiled floor on timber)
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