Drill Porcelain Patio

[Davey]

We’ve recently had a porcelain patio laid and a new brick retaining wall as shown below. For safety reasons I need to fix a number of bolt down posts along the edge of the patio to support a balustrade.

The porcelain slabs are 20mm thick and I know I need to drill through these and fix into the brick / concrete below.

The post bases are 100mm diameter x 8mm high and each one has 3 x 10mm fixing slots. I’ve got some M6 x 80mm stainless steel coach screws and Fischer 8 x 40mm plugs. Will these be suitable?

Any recommendations for dry drilling holes in the porcelain? The Rubi Drygress seems to have the best reviews but I’d welcome any other suggestions? These are available to fit an angle grinder or normal drill - is there any preference or doesn’t it matter?

To allow for clearance, I was going to drill a 10mm diameter hole through the porcelain and then 8mm diameter into the brick/concrete below. Does this sound ok? When I’m through the porcelain, I assume I can switch to a normal masonry drill bit on hammer mode?

Is it worth putting a rubber gasket between the post bases and the porcelain. If so, would 2mm thick rubber be suitable?

Apologies for such a long post! I’ve got 45 of these holes to drill and I’m paranoid about cracking the porcelain slabs! Any other advice or tips welcome.

Thank you.

 

[blup]

Bosch multi construction bits are excellent hard wearing tungsten tipped bits. Worth trying first . Build up the hole size.

 

[freddiemercurystwin]

Always a danger of cracking the slabs in that situation, ideally the post bases would have been bolted directly to the concrete through holes in the slabs, the bases will be sure to flex a little when the posts are lent on, I'd have gone with bigger fixings than that. Or the posts would have been side fixed into the wall but the wall is unsuitable for that. Lack of forethought there unfortunately.

 

[jj4091]

Always a danger of cracking the slabs in that situation, ideally the post bases would have been bolted directly to the concrete through holes in the slabs, the bases will be sure to flex a little when the posts are lent on, I'd have gone with bigger fixings than that. Or the posts would have been side fixed into the wall but the wall is unsuitable for that. Lack of forethought there unfortunately.

Sorry but I have to disagree those bases are designed so that any flexing is taken up betwen the base and the post. Never had a problem with ours, fixed as described, in a similar situation in 20 years. Although the tiles are not porcelain they are only about 8mm thick with no signs at all of cracking.

 

[stevie888]

I tend to agree with FMT but iff your slabs are really well bedded then you'll probably be ok. I would look very closely as I drilled the holes to see if there are any visible voids.

 

[opps]

Bosch multi construction bits are excellent hard wearing tungsten tipped bits. Worth trying first . Build up the hole size.

I do like those drill bits but I can't see them working with porcelain.

The hardest thing I have drilled with those was a concrete fence post. 5.5mm bit, 4000rpm and hammer action. It drilled the hole but the bit started glowing red before long.

 

[opps]

You might be better off with something like the Marcrist CD850 (or similar). It (in theory) is self centering. It works dry and is happy to be used in a cordless drill. They only go up to 8mm, but I don't see that as a problem so long as you push the plugs 20mm+ down. You will a few though.

I would recommend that you contact tech support at Marcrist for advice.

As an aside, should you be using coach screws or screws? Often the posts have covers which slide down over the base. Those types normally require countersunk screws.

Not sure if the rubber will be necessary, but it won't hurt.

 

[blup]

I do like those drill bits but I can't see them working with porcelain.

The hardest thing I have drilled with those was a concrete fence post. 5.5mm bit, 4000rpm and hammer action. It drilled the hole but the bit started glowing red before long.

I suspect 4000 rpm is well above the limit Bosch speecify

 

[opps]

I suspect 4000 rpm is well above the limit Bosch speecify

Good point. Bosch recommend no more than 500rpm when drilling in to ceramic. Strangely, they seem to suggest that cordless drills can only reach 1000rpm.

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