My "opinion" does not matter.  You need a Legal option. I am not licensed to practice law. 

The buyer needs to consult with an attorney. 

I wish you all the best with this. 

1) wow, lots to cover here. Glad you have photos.

2) They bought the house with a double vanity. Now it is gone & I'm wondering why the builder didn't mention the change. Anything that gets changed you notify in writing & add it to the contract.

3) In all my experience, I have never heard of a double vanity being against code. Maybe the plumbing wasn't to code & that should have been corrected by the builder at their cost. Putting in a single makes me think that the builder took the cheapest/quickest solution.

4) So not excusing the builder of notifying the buyers, let's not forget the LA didn't do anybody any justice either. You can almost see this current problem coming down the pike.

5) I'm of the adage that the buyers can get out of the contract but do they really want to? Normally this can get worked out. You might want to just stand your ground.

Thanks for the great question!

Speak with an attorney who can review the contract. I might think they can get out of the contract if the builder can't deliver what was promised but it all depends on what the contract says. 

Interesting.

I'm not aware about such code in CA.

In your situation: one of the features of the property was not in the same condition as when the offer was submitted/accepted. I had few situation like that and had to request the hold of some funds till the situation was resolved.

!You have to consult your broker or attorney what to do so you follow requirements/regulations in your state. 

Lake Sinclair? Where is our specialist Tammy Lankford, 

and what does the contract say? How specific are the features of the home in the contract? I would think if the seller needed to modify the design to obtain C/O they needed to get the buyer's signoff first! 
I would first go to my broker, have them go to Legal and find out how to muscle the builder into compliance or return EM. 

I would seriously challenge the assertion that a double vanity is against code.

In today's market your buyer may not want to walk away, though one of ours did this last year over a construction change issue.

I would suggest that you give notice to the builder that the issue must be fixed and if not done by closing you will require that double the estimated cost will be withheld from sale proceeds and held in escrow until after the repairs are made.

Of course everything depends on your contract and you should really have your buyer talk to an attny asap.

Have the builder change the sink back to double after settlement.

A couple things...did the builder or LA show the buyer the section of the code that the double sink violated? If not, why not? Buyers can also contact the applicable entity in your area (code enforcement, building department, etc) and verify that was true and ask to be shown the specific section that applies to this. It is possible that there was another problem that triggered this so do your due diligence,

Here in Florida our State dues include access to the Legal Hotline which is staffed by attorneys who can point you in the right direction. I would first ask the LA for a copy of the code section that was cited and also check with the city/county department then call the Hotline. If you don't have access to the Hotline, time to contact an attorney.

It's on the builder, not your client and I'd hire an attorney to make sure it's so.

Sounds like a legal opinion is necessary. I do know in MA you need to meet code before you get a certificate of occupancy. They would really walk over a sink? Find a really wide sink...lol

If buyers like house, lot, and location, they should buy it, then change the vanity after they move in. Check with the building dept to see exactly how a double vanity doesn't meet code.

Follow the contract.

We are not attorneys.

Maybe the buyers need to consult an attorney.

Great answers here from Lyn Sims and Kathleen Daniels, Probate & Trust Specialist 

State what the code violation is/was. Builder and contractor should follow universal plumbing codes and city and state codes. Generally you need 21 inches clearance in the front 4 inches apart for 2 sinks and 4 from the tub. When contractor/builder found out at inspection of rough plumbing a change request should have been signed by buyers. Since I don't know what the violation is it's hard to help you- perhaps a dual sink can be added in after closing, use a prefab vanity and get the job card signed off BUT MAKE SURE THE BUYER SIGNS EVERYTHING.  It is the builder's error.  I suspect there are many other issues that buyer is unhappy about and the problem is larger than a sink.  How does the finish carpentry appear to a discerning eye? How long did the construction take vs what you agreed? What other substitutions were made?   In this market the seller should be able to sell the house for more than contracted as things have only gone up UNLESS the buyers picked weird finishes and unpopular configurations. Settle fast so they don't slap lis pendens and the huge time and cost of a lawsuit on you and move on. 

Have you or client contacted the Building Department to confirm that there is a code violation?  Or is this just the Builder and the LA saying that it didn't pass code?

Once your client takes ownership/possession, can they remodel it with a double vanity?  Or will they have to get permitted for that upgrade, and then hit the Code wall again?   

 You hate to see a sale fall through over (what seems to outside observers) to be a minor issue.   Many times in new construction, emotions run high, builders often re-neg halfway through the project, etc.  If profit margins are thin, a builder might try to shave off a few hundred dollars on something like a vanity.

  I hope you can work it out.

Follow the terms of the contract.

This is NOT a good reason or valid reason to cancel a contract legally or otherwise. Furthermore, it is not a perfect world and things happen. Rigidity punishes the practioner. If you wanted the house, here it is. If not, this is a reason to back-out. Tells me YOU really did not want the home plus is systematic of buyer's remorse symptoms too! The price of a sink, the cost to put in AFTERWARDS is so doable code or no code. Get in or get out!

I am not sure what it would take to keep the contract together but best of luck.  

double vanities not to code sounds fishy. 

The code should've been checked long before the final walk-through and certainly before advertising the double vanity as part of the package. I'm not a lawyer (you should consult one), but I think the buyer is right in that the contract was violated and consent to seek the change was not sought. 

You need a local real estate attorney to review the contract to see what options the buyer has. Depending upon the jurisdiction and the judge it could go either way. Good luck!

Everything should follow through or it is potentially a breach of the real estate purchase contract. Your client has proof of the double vanity in place and should work it out with the builder or talk to an attorney.

Things happen.
Has the buyer fallen out of love with the house? Sounds like it.
Cut'em loose. Any help will come back to bite.
However, if they really want the house and the builder won't budge, I would assure the buyer their future does include a double vanity. I think letting a possible $15,000+ deal die over a $3,000 builders vanity does not  makes good business sense.
As others have said, knowing chapter and verse of the transgressed code is essential.

That's an interesting question, especially if the vanity was in the house but not specified in the contract.

A buyer can never be forced to purchase anything.