Screw thread not catching screwing into masonry

Discussion in 'Builders' Talk' started by Daz_col, Mar 23, 2023.

  1. Daz_col

    Daz_col New Member

    I am currently building a raised decking area. I am attempting to attach one of the outer frames/joist supports onto the brickwork of the new extension - which is proving rather difficult.

    The outer frame is a 4x2 timber (screwing through the 2 side). The extension is new and has been built with engineering bricks (therefore has a lot of holes in).

    I have been drilling through with a masonry drill bit with ease. After roughly 40mm of drilling into the brick it gives way and there is no more resistance (could only put this down to the type of brick?).

    So far I have tried:
    1. Drilling a 14mm hole for a 12mm stud screw with Kem fix put in. As there is a collapsed space inside the brick the Kem fix appears useless.

    2. Drilling a 12 mm hole for M10 130mm masonry screws (no rawl plugs).

    3. Drilling a 6.5mm hole for 80mm masonry screws (no rawl plugs). This has been the most successful. However after a few have successful grip the next one i screw in seems to displace the other screws (this also may be down to marginally warped timber, as it has a slight raise in the middle when placed against the wall)

    In summary, my questions are:
    1. What have I done wrong
    2. How do I fix it
    3. Have I messed up the brick work and will it be an issue in terms of water damege? (3 courses of brick above the damp roof layer)
    4. If answer to 3 is yes, what’s the best way to fix it.

    Thanks a lot for any help :)

    Attached Files:

    Last edited: Mar 23, 2023
  2. Ay Bee Cee

    Ay Bee Cee Active Member

    This is what you may have. Although normally the holes would be filled with mortar.

    Are you putting spacers between the brick & timber.

    I prefer to see floating with a void.

    Last edited: Mar 24, 2023
  3. Daz_col

    Daz_col New Member

    I'm not putting a spacer between the brick and the timber. Reason being 1. I’ve put clear treatment on top of the timber and 2. It’s covered by a sil/ledge. Unless I still need to put spacers behind?
  4. Ay Bee Cee

    Ay Bee Cee Active Member

    Or maybe; more likely not to be filled with mortar

  5. Abbadon2001

    Abbadon2001 Screwfix Select

  6. Cris 11

    Cris 11 Active Member

    I just used 7mm drill with brown plugs and 100mm screws 80mm is too short 50 mm is taken up by the timber so only leaves 30mm into brick.

    Its been OK for 10 years now and still going strong I give it a heavy coat of screwfix no nonsense deck oil every autumn, still looks like new.
  7. BillyT

    BillyT Member

    Plastic sleeves for installing resin anchors in hollow substrates are what you need.
    ginger tuffs likes this.
  8. Ay Bee Cee

    Ay Bee Cee Active Member

    Last edited: Mar 24, 2023
  9. Truckcab79

    Truckcab79 Screwfix Select

    BillyT has the right answer. You’re using the right product but only using half the system. Use the anchors. They’re just a perforated plastic sleeve. Resin mushrooms into the void and the fixing then cannot release. It’s designed for exactly what you have.

    Stainless steel threaded bar and spacers if you want it to last. Clear preservative is pointless for what you’re doing.

    4x2 isn’t really man enough unless the deck is tiny. You should be building in 6x2 really. Or use loads of supports
    stevie22 and Abbadon2001 like this.
  10. Abbadon2001

    Abbadon2001 Screwfix Select

    6x2 definitely the job.

    Fix with alternating fixings to spread the load across the full width and height of the ledger :

    Truckcab79 likes this.
  11. Daz_col

    Daz_col New Member

    Cheers all, advice is much appreciated. Going to get my hands on some 6x2, stainless steel spacers and anchors for the studs. Any advice on beat resin product to secure stud and anchors into wall?
  12. Daz_col

    Daz_col New Member

    Also, will I need to patch the many holes across the brick work before I do all this to prevent potential future water damage?

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