The winner is the couple that makes the most profit when their homes go to auction during the season finale.
Both Cat and Jeremy say their first week on the show was intense - especially after being thrown into their first challenge just 20 minutes after arriving on set.
"We weren't expecting it - we thought we would have a bit more time to sit down and think about what we would have to do. Everything being so 'go now' - that was really hard," Cat said.
Jeremy: "We were demolishing straight away, stripping out the walls. But we were also trying to figure out what we wanted to do with the first room - what to remove or what to keep. Finding a builder was a big task, and there was just a lot of uncertainty."
Both admitted they were running on adrenaline, sleeping on site for anywhere up to five hours a night.
"Going to bed really late and still having the energy to get up the next morning, or not getting any sleep at all and having to work through the following day has been tough," said Jeremy.
Cat: "I'm finding the lack of sleep really hard - you run out of energy so quickly, but you have no time to take a break, you just have to keep going."
* The Block's fourth season begins on TV3 from 7.30pm.
- nzherald.co.nz