Unsealing a school playground: soil as sponge, soil as cooling system

Why unseal a school playground? To our mind the answer holds in a handful of moves: strip out the asphalt where it serves no purpose, plant shade trees, let the water sink in; the ground turns back into the sponge and the cooling system of the place. As we said when we wrote about soil first, a square metre of living ground works for free where a square metre of asphalt only stores heat and sends rain off toward drains that are already struggling, in a downpour just as much as in a heatwave.

There is a feeling of summer before there is any argument about regulations. A playground shaded by mature trees, ground that holds its coolness instead of handing it back like an oven, means hours of playtime given back to children on the hottest days, when bare asphalt turns hostile and the shadow of a covered walkway is no longer enough. An awning, a shadow sail, a classroom air conditioner: all of that gets installed, serviced, replaced. A tree planted in the right spot does the work alone, season after season. It grows up alongside them.

That is the wager we made in Chambéry, in the French Alps, together with POESAGES: 320 m² of school playground unsealed and replanted, completed in 2024. Under the asphalt, a soil had been waiting decades to breathe again. We stripped out the bitumen wherever it did nothing but store heat, planted large-canopy shade trees, and let rainwater reach the ground directly instead of running off toward a drain. The project brief puts it plainly: “Turning an asphalted school playground into an urban forest means giving children shelter from heatwaves and giving the earth back its breath.” Neither a gadget nor a symbol: 320 m² handed back to living things, quietly infiltrating, cooling and shading without anyone having to think about it.

We are not alone on this path. Since Paris adopted its resilience strategy in September 2017, the city has been methodically transforming its school playgrounds: by its own count, 203 oasis playgrounds and 5 oasis crèches were in place by mid-2026, working toward a target of 360 by 2030 under its Climate Plan. The method echoes ours almost point for point: natural materials, a preference for open ground, trees, green roofs and walls, teaching gardens, even fountains that give water a pedagogical role rather than a purely drainage one. The benefit spills beyond the playground itself: these courtyards open to the neighbourhood on Saturdays, cool islands offered first to vulnerable residents during heatwaves. An unsealed school playground stops being just a piece of school equipment; it becomes a service rendered to an entire neighbourhood, a few hours a week.

On the ground, the method holds in a few moves, though it takes discipline to apply them. We do not unseal the whole playground: hard surfacing stays wherever the use demands it, a sports court, accessible routes for people with reduced mobility, and the rest, usually most of the surface, goes back to soil. We choose large-canopy species able to cast wide shade without multiplying watering points. We let rain sink in where it falls instead of piping it toward a network that struggles at the first summer storm. Planning law is increasingly pulling the same way: more and more local plans now write in a minimum share of permeable ground, and stormwater zoning pushes, too, toward infiltrating on site rather than sending water further off. Thresholds vary from one town to the next and have to be read document by document, never taken on faith from a brochure, even ours.

A school playground has line markings, deflated balls, a bell that rings on the hour. Nothing of a manifesto. Perhaps that is exactly why the gesture carries so far: stripping out a few dozen square metres of asphalt, planting a tree that will shade children we do not yet know, letting rain find its way back under our feet. Modestly, without revolutionising anything, we give the place back its own capacity to breathe. How many playgrounds, in your towns, are only waiting for that one gesture?