UK Visa Space Standards
The adequate accommodation requirement in relation to the UK spouse (or marriage) visa is designed to ensure migrants do not come to the country and end up living in overcrowded or substandard housing conditions.
To obtain the best advice regarding whether or not your accommodation is adequate, consult an immigration lawyer in the first instance, who can advise you on whether or not your housing meets the required standard and the next best steps to take if it does not.
Overcrowding is defined in the Housing Act 1985, which specifies the numbers permitted for a given number of rooms or given floor area. Account is only taken of rooms with a floor area larger than 50 sq. ft. and excludes kitchens, bathrooms, toilets, etc.