A mysterious street artist is transforming a drab retaining wall in Lower Hutt into a giant Lego set.

Over the past two weeks the faces of Lego characters have been appearing on concrete slabs that make up the wall on Gracefield Rd at the foot of Wainuiomata Hill.

Chatter among locals is rife over who the artist could be and what new faces might be on the wall each morning.

Wainuiomata artist Block Vandal, who spoke to Stuff on the condition of anonymity, said the project was simply about bringing joy to passers-by.

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"I've been driving past the wall for four years and I see the aesthetic of the blocks as a big Lego head.

KEVIN STENT/STUFF Street artist Block Vandal is transforming a concrete retaining wall in Lower Hutt into a massive LEGO playset.

"The idea is to make the community smile and to activate a space that feels dead."

Initially unsure of how people might react to his artwork Block Vandal gave himself just 10 minutes to paint the first slab.

"It was just in and out."

Locals now give him a toot and a wave while he sprays the slabs in broad daylight. Painting two or three blocks a week, he takes about an hour to complete each section.

He crowdsourced ideas for his block works from comments on social media.

KEVIN STENT/STUFF Block Vandal touches up one ofg his works at the foot of Wainuiomata Hill.

The wall features superheros including Wonderwoman and Spiderman, generic Lego faces and a melting man - a statement about global warming.

Block Vandal said the attention his work had received was very positive but he was embarrassed by comparisons with British street artist and activist Banksy.

"[I'm not comfortable with] it at all. I appreciate it, but he's a legend in my eyes - a big inspiration."

The paintings have become so popular the Hutt City Council has promoted the wall on social media.

KEVIN STENT/STUFF Block Vandal believes there are about 100 concrete slabs making up the wall and his ambition is to paint them all.

Council chief executive Jo Miller said the council definitely did not regard Block Vandal's art as vandalism and it was keen to work with him in the future.

Block Vandal's ambition was to fill in every slab on the wall - he believed there were about 100.

Block Vandal's work can be seen on his instagram account block_vandal_.