If you have no space around your home then an extension into the attic or a loft conversion is an alternative to consider.
There used to be a law around the minimum ceiling height, whilst this is no longer a part of building regulations it is sensible to consider a minimum height for practical purposes.
A ceiling height of 1.8m for a shorter person may well work but at some point the house is likely to be sold and anyone taller would be put off! The normal floor to ceiling height ranges from 2.1m to 2.4m. In an attic where there may be sloping ceilings you would want 50% of the floor space to have a ceiling height of 2.1m to 2.4m.
We have developed many attic extensions and loft conversions, if you are looking to extend upwards do give us a call.