How much weight can it take

[GuavaHalf]

A freind lovesing a fairly modern house (no more than 20 years old). In his upstairs study he already has three full bookcases. He wants to add a forth on the same bit of floor. How much weight can this sort of floor stand? Is he in danger of bringing the house down?

[zmudge]

It is not possible to provide you with any meaningful answer through AnswerBank. I would have to know the size of the floor joists, their bearing into the wall, what they are sitting on, centres of joists, flooring, position of lintols, etc etc etc. There is a real danger of partial or total collapse because of overloading, and paper is a very heavy material. As a temporary  precacaution your friend should sit all bookcases on a thick (1") ply sheet larger than the plan area of the bookcase so as to spread the weight over as many joists as possible. The permanent solution is that a Chartered Building Surveyor (not a builder) should be employed to examine the property and make recommendations.

With compliments zmudge/