It’s been a rocky week for Block favourites Bianca and Carla, who unwittingly ran into trouble by breaking a couple of the show’s most stringent rules.

On Tuesday’s episode, the former netball stars were accused of being ignorant of the finer details of their budget, after invoices showed the duo were charged just $500 for more than $10,000 worth of lighting.

In doing so, they broke rule number five of the show, which is that no couple can accept “more than 50 per cent discount on any trades goods”.

A day later, foreman Dan stumbled upon the pair’s electrician doing a spot of painting.

The girls argued that he painted no more than 200 millimetres, while foreman Dan argued it was more like four metres.

“I know there’s probably a technicality, but just quickly using a spray can so the Carpet Court guys could put the blind up seems to me completely ridiculous. We weren’t meaning to bend the rules to try and do that,” Bianca told the producers.

For the record, rule number two in The Block rule book is that all painting must be done by contestants.

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While the show is transparent about the rules being the rules, it does raise the broader question of why the rules are the rules, when contestants are being docked thousands of dollars for actions that may not have an impact on the show’s broader outcomes.

According to the show’s executive producer Julian Cress, it was decided the contestants would do all their own painting to ensure their input on the final product was obvious.

“We try to ensure that the contestants do as much of the work on their apartments as humanly possible. Some works, like electrical, must be performed by licensed trades, but painting can be done by anyone, so we have made that mandatory for the contestants. It is one way of protecting their budget bottom line. If they were able to hire painters they would run out of budget before the halfway point,” he says.

When it comes to accepting discounts, the show decided 50 per cent seemed realistic.

“We chose 50 per cent of the advertised price because we think that is the ‘real-world’ maximum discount that anybody could get from a retailer. We need to have a maximum discount to maintain fairness in the competition, otherwise contestants could leverage their relationships and potentially get product for free.”