I am fairly new to H&S (Nebosh Cert) and am currently working for a company who have a new construction project coming up, which is the internal fit out of a steel framed warehouse unit (2 mezannines, offices, wahrooms, meeting rooms, plant rooms & M&E). The warehouse is 3000sq mtr plus a new additional extension to the side.  The project is being completed by sub contractors who are experts in their fields. Can you tell me what the legal requirement is for fire alarms and extinuishers during the construction phase of the project? I forsee all hot works being covered by permit system and contractors will bring their own extinuishers for hot works. I understand that the answer will depend on the fire risk assessment, which will be completed by a 3rd party company, however I'd like to understand what the minimum requirements as an indication. 

Of course, I would not even think of atempting to do this myself, I am simply trying to find out the requirements so i can improve my understanding. I am booking myself onto the nebosh fire certificate so I can fill some gaps! 

The appropriate guidance for this is HSG168 which is what I would expect the fire risk assessor to be considering when carrying out their assessment. Obviously, I'm not suggesting you carry out the assessments yourself, but from a learning / curiosity perspective you should find it useful. 

Also worth noting that for a general approach to fire safety you should use the Government assessment guides, not BS9999.