Can a conservatory be erected on top of a first floor extension?

It is possible to build a conservatory on top of an extension provided: -Local Authority Planning Permission has been granted – Local Authority Building Control are content with respect to all the relevant parts of the Building Regulations. Conservatories at first-floor level are not exempt from the Building Regulations.

What needs to be done to create a basement in an existing or new house?

Basements require both Planning Permission and Building Regulations approval whether constructed as part of a new property or as a retrofit to an existing property. You will need to consult your Local Authority Planning and Building Control offices
The Basement Information Centre publishes a useful industry guide ‘Basements for dwellings’ on basement design and construction and they can be contacted at the following address:
The Basement Information Centre
Riverside House
4. Meadows Business Park
Station Approach
GU17 9AB

Timber sizes for floor joists – Where can I obtain the timber sizes for floor joists and roofing members that are no longer directly contained in the current version of Approved Document A?

This information is contained in the guidance document published by the Timber Research and Development Association (TRADA) titled: – ‘Span tables for solid timber members in floors, ceilings and roofs (excluding trussed rafter roofs) for dwellings’, obtainable from:

TRADA Technology Ltd,
Chiltern House
Stocking Lane
Hughenden Valley
High Wycombe
HP14 4ND

Or alternatively technical guidance is given in British Standard BS 8103 Part 3 2009 ‘Structural design of low-rise buildings – Code of practice for timber floors and roofs for housing’, obtainable from:

British Standards Institution
389 Chiswick High Road
W4 4AL