Sink cut-out

[eyecatcher]

Double sink and drainer.

cut out in the top surface is normally 1cm all round less than the overall size of the sink.

question is, do I need to cut out the concrete substrate to the same or maybe just the area of the bowls.?

I am pondering on this because, there seems to be no need to cut out the connie under the drainer; BUT....as with most sinks the lip has a clip position for fixing/pulling the sink down againsts the worktop as they can sometimes lift if they are slightly twisted; and it completes the seal around the edge.

what would you do- recommended cut out in both concrete and granite?

[seajae]

ours are the same(actually the concrete hole is slightly bigger), the builder actually allowed for the sink when setting it up so only the granite had to be cut, he pre measured the sink and formed the concrete to allow for the twin tubs, the draining section has concrete under it.

[eyecatcher]

ours are the same(actually the concrete hole is slightly bigger), the builder actually allowed for the sink when setting it up so only the granite had to be cut, he pre measured the sink and formed the concrete to allow for the twin tubs, the draining section has concrete under it.

ok, so in your case the cut out was really only for the sink bowls, albeit a tad bigger to allow for some manoeuvr; manuev.adjustment.

thats what I want to do as a cut out 1200 long with only 50mm back and front is pretty fragile. if you have ever fit a sink in a typical chipboard worktop, that is scary cutting, and you cant reinforce chipboard..

as i mentioned in the op, concreting under this area makes "pulling" the sink from underneath impossible. maybe I am worrying too much.

[bankruatsteve]

Why you would have concrete anywhere near the cutout for a sink is silly. It's not needed for support and just gets in the way otherwise. ???

[eyecatcher]

Of course its needed for support. There is no strength in granite especially the narrow 50mm strips at the front and back edge.

My question is about whether to run the connie under the drainer area or not.

I decided to leave the hole around the bowls only.

[bankruatsteve]

There should be support for the granite on the front and back strips but there is no need to support a sink other than from the (supported) counter-top. One of our workers tried to do that for a double bowl sink we have by putting concrete and rebar in the area between the two sinks. I had to tear everything out so I could install the faucet and the overflow drains.

[blackcab]

If you want to leave the concrete under the draining board you could always add some 1 inch holes in the concrete using pvc pipe placed around the edge of the draining board.

This way you would have access to get the retaining clips on the edge of the draining board from underneath.

A bit fiddly though.

[eyecatcher]

In the end I decided to take the concrete under the drainer if theres a problem thereafter it can be solved as always.

[bankruatsteve]

From the photo, in my opinion you would want to take out the entire section of concrete in the cut-out for the sink. Hopefully no rebar as that will make things difficult. You said that you will be having a granite counter-top? In that case, you have gone way overboard for support needed. Cheers!

[eyecatcher]

Overboard indeed. I wasnt really happy concreting it in the first place.

Anyway the whole job took less than two days.

I have another 40/50mm to play with on the height so the drainer will be no where near the connie...i hope.

Enough rebar in that concrete to sit an elephant on it.