How do you secure a topmount sink to a 20mm stone benchtop?

Trying to securing a sink to a 20mm benchtop and of course the clips don't reach.

Was thinking of gluing 18mm mdf to the underside of the benchtop then screwing the clips in... thoughts or ideas?

 

Worked it out.
Get 16mm mdf and put long pieces under the stone where the sink will clip in.

Also, buy the clips from bunnings. The clips supplied with the sinks are usually crap (well in my case it was - bought a Clark double sink for $260 @ Bunnings).

 

you will definitely need support rails along the top of the Carcasss. Your 20mm benchtop is not strong enough to hold the weight of a sink full of water. Also as you've found out that it helps secure the sink to the benchtop.

 

@Shady when you say the stone isn't strong enough to hold a sink full of water, are you saying the stone will crack?

The mdf I put in isn't that thick in width. The back of the sink has a 42mm x 1800mm x 16mm thick

The front of the sink is only 14mm x 1800mm x 16mm.

The sides which are bracing the front and back piece are 150mm x 510mm x 16mm.

Is what I have sufficient?

 

Did you out a beed if silicone?

 

No I just used the foam.
Was getting mixed reviews with silicon vs foam.
Most opinions were leaning towards foam

 

When they build the carcass for a stone bench top they should (or they used to) put extra support rails along the top. The standard 33mm thick laminate benchtop is much stronger and more flexible than 20mm or 40mm granite or manufactured stone. The 40mm stuff is 20mm anyway, they just double up the edge part so it looks like 40mm and 30mm granite is 30mm thick all the way through, similar to the HMR laminate.
I cant follow what you've done but you'll soon find out if it's strong enough and yes, it will crack the stone

 

@Shady

So this is how the kitchen looked BEFORE Stone install


The 40mm part of the stone simply rested on the cabinets. There was NO rail support, nor was there any MDF.

Here is am image of the stone where the kitchen sink is


Because of this, I couldn't clip the sink in

So i inserted pieces of MDF as per the image below


The MDF rested on the cabinets too, so there was a small gap between the MDF and the stone, so inserted small pieces (darker orange) 3mm MDF where the sink clips were so that I could tighten the sink clips.

I did cut the MDF so that when i installed the 4 pieces, they were nice and tight. Where it wasn't tight, I used a L shape bracket to secure them.

On a side note, can you over tighten the clips?

I'm now worried i completely messed this up. Good news is that I can take the sink out and get it reinstalled... but by who?