Local Authorities do not have to give grants to
extend a house unless it is to provide bathroom or toilet
facilities if this cannot be provided within the current framework
of the building. If an extension to your home does not attract
mandatory grant - for example where this is for a ground-floor
bedroom - councils can decide to give a "discretionary grant". Your
council can choose how it calculates any discretionary grant it
offers so it may very well only cover a small percentage of the
total cost of the works.
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