The Scottish Government revealed the figure as it launched a consultation into an amendment order that proposes three new classes and takes most single-storey rear extensions out of the planning system.
The proposals would create a 1m "bubble" around homes in which additions such as porches, satellite dishes and dormer windows would be permitted development. The consultation estimates that the measures will cut out 4,000 applications a year "without unacceptable risks to public amenity".
Other suggested changes include allowing extensions to occupy up to half of the total site, an increase on the existing maximum of 24m2.
The government's aim is to simplify the rules, which it views as too restrictive. "Considering minor and uncontroversial types of development is not an effective or efficient way of regulating," the paper argues.
"Requiring applications where the system can add no value imposes unnecessary costs and delay to development, leads to regulations being ignored and increases costs for local authorities."
It notes that 97 per cent of the 20,000 householder applications submitted annually in Scotland are approved. Restrictions would still apply in conservation areas and when listed buildings are involved. The consultation runs to 14 January 2011.
The consultation paper is available at PlanningResource.co.uk/doc