What if I have a truss section type roof?

The truss roof is constructed out of thinner sections of wood but the structural integrity is gained by the addition of diagonal brace timbers. Having to remove such braces would affect the structural integrity and a design must be prepared to qualify all the structural elements as there will need to be the introduction of steel beams and a steel ridge beam. The rafters will also have to be increased in size to carry the different stress loads.

Depending on the type of loft design there will more than likely be the need to introduce steel beams to carry the new floor as it is highly unlikely that the existing ceiling joists will have the size and strength to carry the floor structure.

Option 1: Lower the ceilings below
If you are in an older style property you may find that the ceilings below may be high sometimes up to 3 meters from floor to ceiling. If this is the case it is possible to remove the existing ceilings and reinstate then at a lower level providing it is still exceeding 2.4mts to comply with building regulations. This can be a messy alternative but can give you that additional height in the loft.

A tip from the trade.
If your builder suggests this ask him to build the frame and deck out the lower ceiling and seal it before he removes the ceiling above. This reduces the mess and makes it more habitable for the householders during the works. It also makes more common sense.

Option 2: Raising the Roof
This is a major job and will not suit all types of properties. It involves removing part or the whole of the roof and rebuilding it to give it the necessary height and required structure. This can be structurally feasible however the problem comes with getting the required planning approval from the local council. There are other considerations and expense such as purposely designed scaffolding with weather-proof coverings to protect the property during this major modification.