The teams are led by Andrew Burrows, a play development worker with Cardiff council for 16 years. The flat-pack scheme has been praised by the Welsh Assembly government, which wants children to have a bigger say in designing play areas.
The first was built in March 2005 at Splott play centre. "We've put up around 20 structures so far at play and youth centres, and at parks and nurseries," said Mr Burrows, who had been using plastic pipes to create structures.
His original work was backed by a pound;5,000 innovation grant from the funding body Cymorth. But he wanted to get more local people involved and to use wooden logs.
Mr Burrows found a company in Gloucestershire, MacVenture Play, whose steel brackets made it possible to create all sorts of structures using small pieces of wood.
"They were doing basic play structures for the community in their area,"
said Mr Andrews. "We sent them ideas of what we wanted to do and asked if there was any way we could make our structures longer-lasting."
Volunteers, including staff from Halifax Bank of Scotland and Black Horse Insurance, have helped with building. One virtue is low cost: a basic pyramid is around pound;500; a rotational swing about pound;600. "You can put things up really quickly - a 'Toblerone' (prism) can go up in an hour,"
said Mr Burrows.
At St Mary the Virgin primary, in Bute Town, pupils have designed and built an elaborate system which includes tyre swings and monkey bars.
Julie Bowman, headteacher, said: "We've been working for five years to improve playground behaviour. Rather than cut out the volatile afternoon playtime, we wanted to give them some positive tools.
"Andrew and his team were overwhelmed at the enthusiasm, commitment and maturity of the children's ideas."
The Assembly government published a play policy implementation plan in February, saying that "play is the elemental learning process by which humankind has developed".
The plan compels councils to provide for play needs.
For details see: new.wales.gov.uk