Exclusive: Block winners Alisa and Lysandra reveal the secret to a winning bathroom as they continue their Design Duo Series

The Block's 2013 winners Alisa and Lysandra are "thrilled" to be back for a new season of their online series The Design Duo, with the opportunity to finally build their own family homes.

Kicking off Season 3, the twins first deliver their master bedrooms and bathrooms. Quite fitting, as this week on The Block, the five teams will be delivering their master ensuites.

Stream the latest episodes of The Block for free on 9Now.

Speaking exclusively to 9Entertainment, the two-time Block contestants shared their non-negotiables when it comes to delivering a bathroom space.

"First and foremost, bathrooms have to be functional," explained one-half of the design duo Alisa. "It's making sure your layout is right."

You can catch a sneak peek of their new series in the video above.

"I think a definite no would be choosing more than two tiles within your bathroom," Lysandra added.

"We really love using the same floor and wall tiles and sometimes we'll throw in a feature tile. We see people using three different types of tile and we just think that doesn't work," she revealed.

Alisa pointed out that we've come a long way when it comes to bathroom spaces.

"With your tile selection, to different finishes to your tape ware down to your glass selection..." she said.

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"But the biggest mistake a lot of people make is they look at one room isolated. They don't look at all the other rooms they want to design over time, so you'll find the spaces become disjointed.

READ MORE: Looking back at Alisa and Lysandra's top 5 winning spaces after making a surprise return to The Block in 2022

"That's when you start to think, 'Oh my God, I'm getting confused with my styles... this feels jumbled now,' because you haven't taken the time to look at the home holistically," shared Alisa.

In Season 3 of their Design Duo Series – which you can watch on their website – the twins will unveil two new builds that will take place in the seaside suburb of Somerton Park, South Australia.

But this year, there's a twist.

Instead of working together, the 'Twin-Off' season will see the sisters build their family homes side by side, with identical rooms being revealed each week.

"On The Block, the judges get to decide the scores. But this series, the viewers get to decide which sister's design stands out," revealed Lysandra.

We love a bit of sibling rivalry!

With renovations in full swing, the twins shared their number one piece of advice for beginner designers and it involves a very handy hack.

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"Start compiling mood boards," said Lysandra.

"We create one for every project we work on and it's almost fool-proof," she said.

Fans of the current Block series will know House 1's Steph is a huge fan of the mood board / tray, too.

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"Get samples from suppliers and put it all together on a table. It's crazy, you'll know straight away whether it works or it doesn't work," said Lysandra.

"It gives you the ability to play around, and it can be as easy as getting a Word document on your computer, snipping items that you like and putting it on a page," she explained.

Identical twins Alisa and Lysandra won The Block: Sky High in 2013 and went straight back the next year for The Block: Fans vs Favourites in 2014.

Between residential and commercial projects, brand collaborations, and their own brand Al.ive body, the sisters are back on site for Season 3 The Design Duo, out now.

This week, The Block airs at the special time of Monday to Thursday at 7.30pm on Nine and 9Now. Catch up on all the 9Now.