Floored: Southsiders like Ivor Itchdaddy (above) might not believe it, but the trendy buyers are now going northside in search of homes

Q Two northsiders are travelling in a car. The music is turned off and the windows are up. Who's driving?

A: The Garda.

Q: How does a southsider call in a sickie?

A: Daddy, I don't feel well.

Q: What's the first question at a northsider pub quiz?

A: What are you looking at?

Q: What's a creche?

A: When two cars collide in Blackrock.

The schoolyard jokes are never ending and most are more ribald. All are based on the assumption that Dublin's southside is full of over wealthy, spoiled and privileged toffs while north of the river is the realm of the tracksuit wearing welfare chav.

The friendly (mostly) rivalry between Dublin's two halves has been with us for generations and soaked into popular literature, from Roddy Doyle's northsider Commitments ("the blacks of Dublin") to Paul Howard's southsider schmooze Ross O'Carroll Kelly with his South Dublin Guide Book - How to Get By on Ten Grand a Day. It's been on TV with Damo and Ivor and in advertising with the long running Bulmers "north cider/ south cider" campaign.

Jokes aside, each will claim that their side has a distinctly different character to it. Northside villages might be tattier, and the streets narrower, but claim to be far livelier places with less pretention and more craic. Southsiders will cite the elegance of their street architecture, the leafier lanes, wider spaces and politer attitudes. But 250 years ago it was the other way around - the northside with Luke Gardiner's elegant Georgian terraces and squares was far swishier. Then the country's most envied aristo, James FitzGerald, the Earl of Kildare, turned it all on its head by commencing the city's most inspiring private residence. But Leinster House was commenced on the then grubby southside of the city.

So influential was Kildare that his move slowly cranked the fulcrum of city society south. The upmarket squares of Merrion and FitzWilliam followed and filled with O'Carroll Kellys-to-be. And as the northside's best homes were abandoned, they became the slums. Later the wealthy Anglo Irish moved south en masse - for big houses built on private estate lands in the Pembroke and Rathmines councils districts of Rathmines, Rathgar, Ranelagh and Donnybrook. Finally, when the first Catholic middle classes emerged in the mid to late 19th century, they made their homes around the bishop's palace, northside. Lines of class, religion and wealth stereotypes were reinforced.

But two and a half centuries later, might we be set for another unexpected volte face?

A few months ago, Time Out declared Stoneybatter in Dublin 7 to be Ireland's coolest suburb and 42nd of the 50 Coolest Neighbourhoods in the World. The previous year neighbouring Phibsborough was voted the world's 27th coolest enclave. Southside staples like Blackrock, Portobello, Ranelagh and Rathmines were not at the races.

But you don't have to ask Time Out. Dublin's estate agents will tell you (if only off the record) that Dublin's northside now holds the hot spots that enthrall the younger go-ahead professionals with money to spend. They want a house in Stoneybatter, Philbsborough, Drumcondra and Cabra. Twenty years ago they'd have been slugging it out southside, in bidding battles over Ranelagh and Portobello.

Their older equivalents meantime are gravitating up the ladder to Sutton and Malahide and most especially, Clontarf.

South of the river the crash wiped out alot of the 'new money' in D4, leaving its hallowed boulevards to a posh but much older populace. To a lesser extent it's also true of D6.

And these days the Killiney and Dalkey "rock broker belt" of 1990's lore is more like the 'put on your safety' belt. All the trendy stuff, as Time Out discovered, has been happening north of the river. So it makes sense that young home buyers are following. Even Dublin's hipster HQ hopped the river divide last year when the GB Shaw Bar abandoned Portobello and re-emerged northside in Glasnevin, albeit amid a controversial northsider/southsider social media notification campaign. Suffocated by outmoded rack renting retail leases, the southside is drop kicking business across the river.

What's more, with the environment now ranking high among younger wealthier buyers, traditionally outsized southside abodes that are simply too big to be retrofitted, are just not on the menu. Go down a rung and Dublin house prices are such that middle-class young professionals from both sides of the river are faced with the choice of acquiring a three or four-bed semi in the commuter belt, outside the city altogether; or else heading straight for edgier north central with its cool bars, cafes and eateries. Here two-up two-downs can still be got for under €380k and family homes of character for €450k. For self-employed self-starters who work off laptop and phone, it's been no contest for some years now.

It started with Stoneybatter in the 1990s amidst a city centre revitalising with Section 23 apartments. Previously those who graduated from city central flatlands bought first homes in the suburbs. But those who started out in the new apartments really enjoyed the growing and lively city centre social scene and didn't care much for a twice daily submersion in ever-thickening suburban traffic.

Stoneybatter's terraces ticked the boxes. Young lawyers, creatives and those working in the arts in particular bought them, ditched the car and started their families there. And when it came to trading up, they looked to their doorsteps. The ban on bedsits and the wipe-out of pre '63 landlords brought lots of affordable and manageable mid-sized period houses to market in D7 and D9 ready for refurb.

But it was the arrival of northside Luas that blew it into orbit. And the new DIT Grangegorman campus, the success of the IFSC and proximity to the social media hub. Overseas professionals voted with their feet to live in D1's IFSC. So now Phibsborough is the new Portobello, Stoneybatter the new Rathmines and Clontarf is the new Ballsbridge.

Q: What is a southsider doing in a house in Dublin 7?

A: Calling a mortgage broker. Fast.