Undermount sink fitted without supports

[YorkieSelfBuild]

Hi, I bought a DIY Kitchens kitchen and got an undermounted sink elsewhere. 

 

The kitchen's been fitted, with a MDF worktop while I wait for the granite worktop to be installed. But the sink has no supports underneath it, it's resting just on the sink unit which has a crack now.

 

The builder is saying DIY Kitchens should have supplied the supports but surely it depends on the sink I chose? And it's the fitter's job to know undermount sinks need extra support.

 

The question is does the sink unit need replacing (from builder's pocket) or would a length of wood underneath it reinforce it enough?

[Nickfromwales]

Granite installers should notch cut the underside of the worktop and install stainless dog ears set into resin, plus bond the sink also. 
 

Between those two measures, the sink should be plenty well fixed. 
 

Builder should 100% have supported this as a temporary install. A carpenter would very likely have offered this up as a solution.

 

TBH, you can just fit a piece of iron on edging afterwards, once that cracked timber has been bonded and clamped to the granite. 

[YorkieSelfBuild]

That's great, thank you. I don't want more delays to finish the kitchen, granite installers are due this Friday. I'll email them about the crack and if they can still install.

 

Do I still need the steel support bars like this one?