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Discuss Fitting toilet to concrete subfloor in the Bathrooms, Showers and Wetrooms area at

  1. trf0412

    trf0412 Member

    I need to drill 2 holes to fix a toilet to a concrete subfloor, which has porcelain tiles laid on top. As it's only 2 holes, can I get away with using a Makita combi drill and taking it slow? Or do I really need to think about getting hold of / renting an SDS drill?

    NB. I have a carbide-tipped 10mm tile drill bit to get through the tile, and a Bosch 10mm Multipurpose drill bit (will this be ok going through concrete?)
  2. gmartine

    gmartine GSR

    DO NOT USE SDS....your combi (with hammer off) should be fine with a tile drill or diamond hole saw which are just a few pounds from fleabay.
    • Like Like x 1
    Last edited: Feb 28, 2018
  3. trf0412

    trf0412 Member

    As far as I know, I've only ever drilled into brick/blockwork, so have no idea how difficult it is to get through solid concrete... hence the question. Thanks!
  4. gmartine

    gmartine GSR all means use hammer (percussion) action once through the tile and into the concrete floor. If you use hammer or SDS on floor tile there's a good chance it'll crack.
  5. trf0412

    trf0412 Member

    Yep, that's what I was thinking. Don't think I'd get very far without hammer action. My drill has 2 speed settings... with concrete, is it better to use the faster setting or slow-and-steady on the slower one? (For brickwork, I find I really need the faster setting).
  6. gmartine

    gmartine GSR

    The tile is actually a harder material than the concrete, that's what I'd be worried about if I had no experience (See youtube). Drilling through concrete can be like drilling through hard brick which you do have some experience of, hammer action doesn't really work efficiently at slow speeds.
    • Like Like x 1
    Last edited: Feb 28, 2018
  7. SimonG

    SimonG Trusted Plumber Top Contributor!!

    The concrete is not your problem. It's getting through the porcelain.
    • Like Like x 1
  8. Best

    Best Trusted Plumber Top Contributor!!

    A good combi drill might be fine for drilling the concrete with decent masonry bit, particularly if you take your time. Depends on quality of the concrete (it gets harder with age).
    I like to drill the tiles with a slightly wider final bit, so to keep from damaging the tile when drilling below it, plus it allows the screw some room to angle
    • Like Like x 1
  9. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Definitely buy the appropriate tile bit to drill the porcelain, if you have not ever drilled a porcelain tile , you will never believe how hard they are , we are nt joking .
    Please use the instructions that will come with the bit .
  10. king of pipes

    king of pipes Trusted Plumber GSR Top Contributor!!

    Just fitted a quadrant shower cubical to porcelain tiles you will need a specialist drill bit to drill them and a water spray to keep it cool while you do the drilling on the high speed good luck . kop
    • Like Like x 1
  11. trf0412

    trf0412 Member

    Hmm... think I might do a practice run (or two) on an off-cut of the same tile! Thanks for the tips.
    • Like Like x 1
  12. Allgoode

    Allgoode GSR

    If you are drilling through porcelain then as above using specific drill bit, albeit slightly wider than hole you will be drilling into concrete.

    You may find it awkward to start the hole drilling but i usually start the bit at a slight angle until it's possible to slowly rotate to the vertical position.

    Also as you will be drilling through a floor tile a good thing to do is to construct a small dam around desired hole area and fill with water.

    Effectively you then have a coolant reservoir to keep your drill bit cool.

    Also if you have a small plastic tub, partially fill with water & dip/spin drill bit in it to clean residue off during the drilling process.

    Keep reservoir topped up with fresh water as dust generated during drilling will form a paste.

    I usually take it nice & slow personally to get good clean hole & prolong drill bit life.

    Hope this helps,

    • Agree Agree x 1
  13. oz-plumber

    oz-plumber Plumber

    Bosch make drill bits for porcelain tiles.
    No need for water or cooling the bit.
    They don't last long, but they're quick, and if you only need to do 2 holes, I would go out and buy one.

    I have worked out a way to get through porcelain tiles quite quickly.

    I do about 4 holes to the average persons one.
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