Billy Fleming and Zach Stephenson are sitting on a set of metal stairs outside Wollongong's Rad Bar. Zach has just noticed Billy has folded the toes of his socks back inside his shoes, so the logo - of Californian punk band Suicidal Tendencies - is visible under the hem of his skinny jeans.

"They're just folded back. These socks are huge," Billy says, shaking his shoulder-length sun-bleached hair out of his eyes.

"Put your socks on properly. You've just got to have the Suicidal Tendencies showing, don't you?" Zach ribs.

It's a snapshot of the duo's chat with the Mercury, but a microcosm of the relationship they have as rising surf-pop band Hockey Dad: they're mates first, bandmates second. Billy, 19, and Zach, 20, are sitting outside Rad about an hour before they will play the second of three sold-out shows in Wollongong.

It's 2pm and, after the afternoon's all-ages show, they have a late-night gig to prepare for. This time of day, Zach and Billy would usually be in the surf or skating. They're happy friends, and fans have taken the time out on a Saturday afternoon to be on time for the show.

"Seeing people rock up now, at two in the arvo, it's cool. We've been seeing a lot of cool little things like that recently, we're starting to see the progression," Billy says of the band's evolution from backyard noisemakers to tour headliners.

"The tour has been crazy," Zach says.

"Even the shows we thought weren't going to be good, turned out to be the best. On the Gold Coast, I didn't think anyone would even turn up but that was the best show yet."

On the back of new single Can't Have Them, the band announced a modest run of dates down the East Coast. The shows kept selling out. Tickets for Wollongong and Sydney gigs disappeared almost instantly, with second shows added. A third was added for Wollongong, then one Melbourne show became two, and tickets for their second Sydney show also ran out.

"That reaction makes us feel more confident, but there's also more pressure too. We actually have to play good now, we can't just go out and get drunk every night," Zach says, laughing.

It's not a bad start for two guys from Windang, a suburb best known for the bridge leading to the next suburb and a low-budget computer store television commercial featuring the immortal line "WINDANG ROAD-A-WINDANG".

Their current success can be traced back 15 years, to a football game in a Windang front yard before they started primary school.

"We lived two houses down from each other," Zach says.

"We were friends from a game of footy out the front," Billy adds. "Me and dad were playing, Zach strolled past and started playing. That was it."

A childhood spent playing sport and surfing morphed into a musical endeavour when Zach started playing guitar, and Billy was shanghaied into bashing on Zach's dad's old drumkit.

"We were just little groms, playing heaps of sport, but then we started surfing heaps and everything else went out the window. From then, it was just surfing and music," Billy says.

Hockey Dad emerged from an earlier band, Abstract Classic, that "fizzled out". Zach had been writing songs on his own, including Seaweed, a staple of Hockey Dad's live sets.

"Billy helped me record some songs, and he said he'd play drums. That was all it was," Zach says of the band's humble origins in 2013.

They took their name from a blink-and-you'll-miss-it sight gag from a classic episode of The Simpsons. From there, local support slots rolled into local headlining gigs, which turned into touring slots with leading Australian bands, and now their own headlining tour.

Along the way they recorded with hotshot producer Tom Iansek (of Big Scary and #1 Dads), made the finals of Triple J Unearthed High, scored radio play across the country, played at Falls Festival in Byron Bay, and made friends in all the right places nationwide.

A week earlier, Hockey Dad are on stage at Rad, the first home-town show they've played in ages and a welcome return after a long slog on the road.

Clad in a vintage Rusty surf shirt at least four sizes too big, sleeves down past his elbows and the back billowing like a cape, Billy slides in behind his drumset while Zach plugs in his guitar. The show is sold-out, but perhaps a few fans forgot they had tickets, as the wooden floor of Rad is less crammed than its usual sardine-like atmosphere; but, when the simple guitar chords and rolling drums kick in, the crowd shift into high-gear from the first.

Zach's warm, jangly, guitar tones wash over the sound, his high wailing vocals telling tales largely lingering on beaches and babes. He wanders the stage, bouncing off the crowd and offering up his microphone for fans to sing, or slur, back at him.

But it is Billy who is the real source of the band's energy, both live and on record. Head down and eyes closed with a grin creasing his face, he plays with joy and effortlessness. Hair swinging, his drumwork is cymbal-heavy and splashy, bouncing and rolling. It's not hard to tell he's happiest on a stage, sticks in his hand.

The gig stretches on and things get rowdier. An older gentleman called Martin, a Rad regular in shorts and thongs, is hoisted onto shoulders and carried around like a king. Drinks are sculled. A kid climbs a staircase and plunges several metres onto the heads of the unwary, before crowdsurfing from the front of the venue to the back. This is summer music, full of jubilation and joy despite the lyrics' teenage angst over girls and boredom.

It's unpretentious and honest, like its creators.

"They're just honest, relatable guys. There's no ego, they just enjoy playing music," Ben Tillman says of the band.

He would know. One of the creators of the Yours & Owls brand, which started life as a cafe and has since become almost a shorthand for live music in the Illawarra, with festivals and a booking agency under its belt, Tillman has watched the Wollongong music scene shift and change, grow and shrink and grow again. He saw Hockey Dad's potential early, and signed them as the first band on his Farmer & The Owl label, a collaboration with record store Music Farmers.

"The guys are like everyone's little brothers. They were new, they were exciting, and they were really good. It made sense to start the label with them," Tillman says.

The duo recently wrapped up recording their debut album, due for release later this year on the Farmer & The Owl label.

Yours & Owls and Farmer & The Owl have been driving forces behind the "Leisure Coast" movement, a loose collective of musicians, artists and creatives cultivating a thriving alternative culture. From bands to painters, blogs to cafes and stores, the Leisure Coast is about being proud of the Illawarra and all it has to offer - not embarrassed and trying to hide that heritage. Hockey Dad, big advocates of their Windang town, slot nicely into that ideology.

"We want to push this area and be proud of it, and Hockey Dad are stoked to do that too. It's a lot of their appeal, being young surfer dudes who are happy to be from Wollongong," Tillman says.

The band agree.

"Even now, we don't say we're from Sydney, we tell people we're from Wollongong, and people are surprised that anyone would even start a band here," Zach says. "What's happening here is still almost under the radar. It's cool to see how much independent underground is happening."

Billy says it's even more basic than that - they just love coming home to play in front of their friends.

"It's always nice coming back to a good reaction. You want people in your home town to like you. Lots of bands make it elsewhere and then they don't come home. We didn't want that," he says.

"There's some great stuff coming through Wollongong. There's something good going on here now."

The boys have another big tour coming up, a 14-date cross-country trek as opening act for two Brisbane bands, indie-pop outfit The Jungle Giants and rockers Art of Sleeping. Starting in Fremantle on September 4, the tour snakes around the bottom edge of the country through Victoria, takes in Sydney, Canberra and Brisbane, then back down to Tasmania. Beyond that, the boys say their musical future isn't nailed down yet.

"The tour will be big, and then hopefully we can go overseas. There's a lot of stuff floating around," Billy says. "I still don't take this seriously. It's actually weird that people turn up to the shows.

"I still turn up to every show thinking nobody will be there."