To strengthen the attic ceilings use metal or wooden beams. Consider the load that will have to withstand the attic. At the same time think over, what staircase will connect it to the lower floor.
There are many options. If the house and attic - "summer", the staircase is quite possible to bring out into the street, making up for it in advance shed or shelter from the weather. In other cases, the ladder is usually derived in the hallway or living room. Remember, the more bias ladder, the less it is convenient, and the slope of more than 45 ° is generally considered dangerous. It makes more sense to set pace stair (with two sites between spans) - go up and down on it very comfortable, and most importantly, safely.
That there is enough light, set a special roof window. Facade window will not work, it does not allow to get the most light. Remember, skylights in the roof of the transmitted light is 40% more than vertical windows. Refer to the figures: for every 10 square meters of the attic should be not less than 1 square meter of glass, otherwise the attic to get dark, and will remind the basement.
Now about the insulation. Not worth saving - attic loses heat much faster than the lower floors, as contact with the environment more. Roof winter hardly keeps the heat in the summer as it is heated to 100 ° C. To select non-flammable insulation and vapor barrier insulation materials, such as stone wool or thick glass.
Insulation thickness is selected according to climatic conditions. To protect the insulation from roof leaks close its special moisture-proof membrane from the roof
Now proceed to the interior decoration of the attic. Use wall paneling, drywall or wall panels - all depends on your overall style. Each version of its advantages: wall paneling looks the most natural, drywall can be painted or wallpapered, and wall panels "spend the winter," even in an unheated room. The main thing is to stick to moderation and do not clutter the attic details.