Ground floor slabs and garages

Yesterday it rained and the site was closed. Today the ground floor is being prepared. A proprietry system, consisting of precast joists and polystyrene filler blocks, spans the 5 metres between the two ground beams that mark the façade. Tomorrow afternoon the concrete will be poured to complete the floor structure for the entrance hall, the passage under the house and the garage.

The planning requirements stipulated that each new house must have a double garage. With the flood regulation a garage is the only use allowed for the ground floor. So there we have it, a ground floor almost entirely devoted to the car (and one or two bicycles).

The Client will be the proud owner of a double garage she doesn't need. She has a car, for which she has very little respect, considering it a heap of metal and a liability. As far as she is concerned the car can stay outside on the pavement. Bringing a car in out of the rain, in her eyes, is very probably seen as a sign of anal retention.
You can oblige people to build off road parking in the suburbs but can you enforce their use? The popularity of a Mayor that installed parking meters in a suburban residential street would take a serious nose dive. So what is the purpose of obliging off road parking? Maybe I'm missing something - could it be that once you have built your obligatory double garage the ratable value of your house is increased and consequently you pay more tax. As this is the national sport I wouldn't be surprised. Maybe the offroad parking means you can have more room for planting trees in the street? Does the double garage incite the purchase of yet more cars. Anyone know the answer?