Is an offer binding or are deviations allowed?

Yes, I will try it like that now...

I was at his supplier... that he charges higher prices for the bricks is not true, he also uses the Creaton price list. In addition, he charged us for the dovetail tiles on the garage and house, but only installed them in the house. Ventilation tiles, which allegedly are only needed with these bricks... that's not true either, you also need them with the more expensive ones from the first offer, but he simply forgot them there...

Left all the rubbish in the garage (wood, pallets, insulation), we now have to dispose of all that as well...

Overall, no service I am satisfied with and paying more than agreed.

The only response to our offer to come to an agreement was, and this is no joke: "Forget it, never ever."

We analyzed the offer again and reviewed all our correspondence; it is even more audacious than we thought.

In the last email before the start of construction, it was recorded: execute the garage without visible roof truss and the house without dovetail.

There was also an email where we told him which tiles we wanted, that these are much cheaper, and asked him to update the offer, which he did not do.

We now have dovetail on the roof even though it was not commissioned, and not only is it not listed on the invoice for the house but also for the garage.

And another email from him:

And if I charge 20,000 euros for the tiles, then I will do it that way and you can do nothing about it because they are not listed in the offer....

In writing....

That’s how you imagine cooperation.

Where can I find information in the law or elsewhere about what is permissible in an offer?

Where can I find information in the law or elsewhere about what is allowed in an offer?

In principle, everything is allowed in an offer: I offer to build you an 80 sqm bungalow for 1 million euros. If you want a mailbox attached, I will do that for an additional 50,000 euros.

You have to be careful not to confuse the terms offer, order, and billing.

Did you commission one of the offers in writing?

So I think legal advice wouldn't be wrong here, or advice regarding what he must reliably be paid and what he may have done without an order, etc., and can therefore be deducted. Not that you fall behind with the payment, but also not that you pay him too much. I would definitely contact an expert for that.

As an example, the dovetails on the garage would probably have to be deducted, as they are not listed. The other tiles, a professional really needs to handle those. Just because they are fundamentally cheaper doesn't mean he can't sell them to you at a higher price, so I would be cautious at first. It could become a problem that you don't have a new offer for that; it might help that you requested it, but otherwise he can probably set the price for the tiles himself.

File a written objection, thereby disputing the invoice.
Pay the agreed purchase price, calmly withhold a little so that he cleans up his mess and a bit more because it was not performed as contractually agreed.

No more than that, then he should explain where the additional amount comes from. Especially considering the existing emails and the original order.
He probably has a written order from you for the corresponding price.

I don’t understand how one can argue like HelpHelp. Just because of the Aktuell Bau boom, the fellow construction companies still have to follow certain rules. If he doesn’t feel like writing an offer, he should leave it and take orders where he doesn’t have to write offers.
The craftsmen shouldn’t be surprised about the increasing bureaucracy for them, because they are responsible for it themselves, as in quite a few cases problems arise in billing because it’s not clearly agreed with the customer or there is an attempt afterward to get a little more out of it. Like in this case here again.

We also had problems with an excavator contractor.
We agreed on something orally, a fixed price. Then we received a bill where it was charged by the hour. I politely asked how this could be. The answer was that it just took that long and that’s how he always charges.
I pointed out our agreement to him, but he wasn’t interested.
So we hadn’t even completed half of the work and the invoice was more than twice as high as the agreed final price.
Then I consulted a lawyer about the procedure if it came to a court case.

The court looks at the work performed and then considers similar cases to see if the prices are similar.
The work performed is calculated with the average value of the comparison cases. The amount in dispute is then formed from the calculation of the average value for the work minus the demanded final sum in the dispute.
The court then recommends a settlement where both parties bear half of the amount in dispute.

If your craftsman is sure that he is owed more money, he will take the legal route.
If he knows he wants to rip you off without any legal basis, he will refrain and be glad that you pay him the full price despite his behavior.
Because if he gets a slap in court, he has lost a lot of time, possibly gets no more money, and also has to bear the lawyer’s costs etc.

In our case, there was no court case.

I paid half of the agreed purchase price and then terminated the oral contract in writing with immediate effect.

Whenever I see the contractor somewhere now, he makes sure to gain ground because he knows exactly that he really messed up and got caught.

So stay calm and don’t pay more.

Basically, everything is allowed in an offer: I offer to build you an 80 sqm bungalow for 1 million euros. If you want a mailbox on it, I'll do that for an additional 50,000 euros.

You have to be careful not to confuse the terms offer, order, and billing.

Ok, so one more attempt to sort this out: we received 3 offers, the last one is in our opinion the one we accepted, because after the 2nd offer we requested to remove the dormers and simplify the garage. We have an email where he responds last: attached is the offer as requested adjusted without dormers and with a simple garage.... BUT there is no email from us saying: ok, accepted as is, so probably no written order exists.

And then we received a billing = invoice that contains completely different items and is higher than everything we had been offered before.

On a personal level, he is angry because we told him we are not satisfied with his work (forgot the nail sealing tape, no vapor barrier) and now he wants to rip us off...... he writes in an email: I can charge whatever I want for the bricks.

And regarding the bricks, I just spoke with a lawyer from the Homeownership Association: no, that’s not how it works. If the Ferrari is in the offer, but then there is a Fiat Punto on the roof, I don’t have to pay for a Ferrari.

I calculate exactly what I have on the roof and am even kind enough to pay for the stupid dormers even though I never ordered them.

I pay for what is on the roof and not a cent more.