Expanding foam and polystyrene

Discussion in 'Help with all other issues' started by Squag1, Nov 16, 2018.

  1. Squag1

    Squag1 Been there, and had one Club Sponsor

    Need to block off a hole in cavity wall where wires come through. Wall is being cavity filled- plastered externally.
    The plan is to close the edge of the hole by filling the cavity.

    Do these materials co-exist?
     
  2. andyBeaker

    andyBeaker Moderator Staff Member Moderator Club Sponsor

    It's certainly one way of doing it. How big is the hole?? Can you post a picture??

    If you use foam it won't be easy to get a good surface to decorate on.

    If it is where there was a three pin socket I would leave the back box in and fill with plaster.

    If it is a bigger hole I would patch it with a piece of brick/block then plaster.

    Easyfill plaster is brilliant if you aren't confident using plaster - it is designed to be sanded to a good finish, works a treat.
     
  3. Squag1

    Squag1 Been there, and had one Club Sponsor

    It's about 6" x 9".
    It's where the hank of wires come from the upper floor to the fuse board in the garage. So beauty isn't an issue.

    I want to leave the hole and seal the cavity as wall is being insulated - not my house - basically making a doughnut of foam around the edge of the hole.
     
  4. andyBeaker

    andyBeaker Moderator Staff Member Moderator Club Sponsor

    Hmmmm.

    Problem with expanding foam it it, er, expands and goes everywhere, possibly into the fuse box? Also might be a pain if any alterations are made to the wiring in the future? From what you have described I wouldn't use foam as it is so hard to control. Also I a must not sure how it rates in terms of flamibilty, obviously a no no if near the fuse box.

    A pretty solution might be to cut a piece of plastic pipe to length, cut a slit in it end to end then slot over the wires followed by plaster/cement round the outside.

    A less elegant but effective solution might be to simply stuff the hole with loft insulation. Then screw a bit of ply/plasterboard over the top to hold it in place if needed. Will eliminate any draught but be careful not to compromise the inside of the fuse box.
     
  5. Squag1

    Squag1 Been there, and had one Club Sponsor

    The objective is to keep foam away from wires altogether. Using fire regarding foam into the cavity only. Will cover hole with maybe plaster board.
     
  6. andyBeaker

    andyBeaker Moderator Staff Member Moderator Club Sponsor

    If you haven't used foam before go really, really sparingly.

    It really does expand you know:eeeeek:
     
    • GROAN ! GROAN ! x 1
  7. Squag1

    Squag1 Been there, and had one Club Sponsor

    All done.
    Tried to upload pic - too big(usually do a screenshot first) Did screenshot but it didn't show in files!!!
     
  8. Oldandbald

    Oldandbald Old Hand Club Sponsor

    Have a sprayer full of water to hand. When it's expanded to your requirements give it a squirt. It just stops expanding.
     
    • Informative Informative x 2
  9. Squag1

    Squag1 Been there, and had one Club Sponsor

    Screenshot_20181118-193233_Gallery.jpg
    But how can you fill the hole around wires going into the floor space without causing potentially overheating problems.
     
  10. Squag1

    Squag1 Been there, and had one Club Sponsor

    Thanks useful to know.
    It does say to spray area before using.

    I wanted it to expand as much as possible and then trim it.
     
  11. andyBeaker

    andyBeaker Moderator Staff Member Moderator Club Sponsor

    As above, cut a piece of plastic waste pipe of suitable diameter to size, then make one cut lengthwise then ease over cables so it closes around them. Leave enough room for additional cables in the fire.

    You could also use plastic trunking with a removable cover but you would probably need to buy about 100 times more than you need.
     

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