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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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    • CommentAuthorTriassic
    • CommentTimeMay 30th 2015 edited
     
    I'm about to start first fix plumbing and having drilled holes through a number of joists, I find the pipe is a snug fit through each hole.

    Should the pipe be a snug fit, or should I drill the holes a little bigger so the pipe is a slack fit?
  1.  
    I've drilled all my service holes a few mm larger than they need to be to allow for movement/expansion. They don't need to be tight to support the weight
    • CommentAuthorCWatters
    • CommentTimeMay 30th 2015
     
    Guide on where you can drill here..
    http://www.stevenage.gov.uk/content/15953/24595/24598/22-GN-Technical-Notching-of-Joists-May2011.pdf

    Should be some clearance around the pipe. If it's tight you can get noises as the pipes warm up.
    • CommentAuthortony
    • CommentTimeMay 30th 2015
     
    if plastic pipe snug is OK if copper NOT OK.
  2.  
    id drill bigger holes
    • CommentAuthorcjard
    • CommentTimeMay 31st 2015
     
    Given that you'll have to thread most of every pipe run through every joist to minimise jointing, it's a lot of potential resistance you could be adding to your pulling effort.. Like the others say, go a bit bigger

    For other services you may end up running through joists, consider whether the service will vibrate, or contract/expand. Vibrating services (air ducts for MVHR for example) should have a gasket of something like foam to help reduce vibration noises transmitted to joist. Services that contract/expand should be able to move freely in the relevant direction (parallel to the pipe direction) but bear in mind that you can also get a banging noise for water systems when the tap is shut off suddenly if the water intertia in the pipe can make the pipe jump and hit something. If your joists will have insulation between, consider your wiring routing and where you drill your holes. Burying a wire in insulation affects it's current carrying capacity. If in doubt consult an electrician
    • CommentAuthorowlman
    • CommentTimeMay 31st 2015
     
    In addition to what others have correctly said, practically speaking, you are going to "have" to drill them bigger if you're most likely doing on site drilling. Lining them up isn't too big a problem but getting the hole true and perpendicular to the joist is difficult when drilling with a hand held drill and even a few millimetres out of true with a snug 15 or 22mm drill will result in you over forcing the pipes through. Drill bigger and foam around afterwards.
    • CommentAuthortony
    • CommentTimeMay 31st 2015
     
    We drilled all joists while in a stack, humps up, and all the holes perfectly lined up, some didnt get used but we obeyed the rules,


    qed


    I hate letting plumbers or electricians drill holes, heathens...
    • CommentAuthorcjard
    • CommentTimeMay 31st 2015
     
    And then there were metal web wonders..
    • CommentAuthortony
    • CommentTimeMay 31st 2015
     
    If you are rich, yes
    • CommentAuthorcjard
    • CommentTimeJun 5th 2015
     
    Are they that much more Han timber I joists when all things such as taking days to whack them full of holes is factored in?

    I've got I joists in my place, 245 deep and a range of thicknesses A to D. Far as I could make out A was four quid a metre, and you add a quid every letter.. An a is 45mm wide and a D is 90 I hink
  3.  
    I would definitely go for metal web if I had my time again. I've done some work on a project with them and they still need care as the edges are sharp and will damage cables or pipes pulled against them.

    However, if you're fitting MVHR then there is a lot of work to get the pipes through and extra expense as you almost certainly need to pay for reinforcing plates as well - 75mm flexi duct is over the allowable hole size.
    •  
      CommentAuthordjh
    • CommentTimeJun 6th 2015
     
    Posted By: Simon StillHowever, if you're fitting MVHR then there is a lot of work to get the pipes through and extra expense as you almost certainly need to pay for reinforcing plates as well - 75mm flexi duct is over the allowable hole size.

    You mean extra expense with the metal web joists or with I-joists?

    I used the flattened semi-rigid ducting and that pulled through metal web joists without too much problem. There was room for two ducts above each other (or crossing) where required.
    • CommentAuthorYanntoe
    • CommentTimeJun 7th 2015
     
    If you fit copper pipe tightly, you will be driven mad by the clicking noise produced by expansion contraction.
    It's really worth spending time making the holes sufficiently big to allow for some movement.
    Usually happens in the bedroom so that you are woken each morning by the clicking pipework just before the radiators get hot!
  4.  
    Extra expense with timber I joists.
  5.  
    I lived in a house where the noise of the copper pipes expanding and contracting when the heating came on was very annoying. In addition to making the holes a bit bigger, there might be a way that the pipes can move over the surrounding material more smoothly so that there is little or no noise.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 8th 2015
     
    Isn't it best to have one of those crinkly bits of pipe every so often. They allow for expansion and contraction.
    I had a house with creaky pipes, it is annoying. Now I just have creaky flooring, which is even worse.
    • CommentAuthorDarylP
    • CommentTimeJun 9th 2015
     
    COP, there is...
    little swatches of dense 'wrap-around pipe lagging laid in the notches/holes, to allow the pipes to expand/contract smoothly without picking up on the timbers.

    Cheers:smile:
    •  
      CommentAuthordjh
    • CommentTimeJun 9th 2015
     
    Posted By: SteamyTeaIsn't it best to have one of those crinkly bits of pipe every so often. They allow for expansion and contraction.

    That's why there are apparently unnecessary doglegs in long pipe runs, to allow the expansion to be taken up by minor bending. Basically anywhere there's an angle it allows for expansion.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 9th 2015
     
    Copper has an expansion rate of 16.6 x 10-6 m/m.K
    how much does a pipe need to move to make a noise?
    •  
      CommentAuthordjh
    • CommentTimeJun 9th 2015
     
    Posted By: SteamyTeahow much does a pipe need to move to make a noise?

    What's the wavelength of sound at say 1 kHz?
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 9th 2015 edited
     
    0.344 m

    So that would have to be divided by the temperature difference before movement takes place, and does not take into account any stiction.
  6.  
    Noise from copper pipes will come from thermal expansion and also shunting as water and air in the pipes is forced through the system by the pump. If the pipes are not secured they will vibrate and move.
    • CommentAuthorrhamdu
    • CommentTimeJun 9th 2015
     
    <blockquote><cite>Posted By: djh</cite><blockquote><cite>Posted By: SteamyTea</cite>how much does a pipe need to move to make a noise?</blockquote>
    What's the wavelength of sound at say 1 kHz?</blockquote>
    Things don't have to move by a whole wavelength before they make a noise.
    • CommentAuthorDarylP
    • CommentTimeJun 9th 2015
     
    It is the pipes expanding length-ways that makes the noise, as they pick up on the wooden members, then 'jump'.
    Hence the 'funny dog-legs sometimes found.

    Cheers:smile:
    •  
      CommentAuthordjh
    • CommentTimeJun 10th 2015
     
    Posted By: rhamdu
    Posted By: djh
    Posted By: SteamyTeahow much does a pipe need to move to make a noise?

    What's the wavelength of sound at say 1 kHz?

    Things don't have to move by a whole wavelength before they make a noise.

    Yes, I realized I'd asked a stupid question once ST gave the answer :shamed:
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