strengthening joists for a loft conversion

[fatty]

Please help if you can:

If I wish to board out my loft for use as storage do I need to strengthen the joists (currently 10 cm deep - 4x2)?

If I wish to convert my loft into a habitable area how do I go about strengthening the joists? Is laying some extra 3x2 perpendicular to the existing joists adequate? What would you do at the ends of these added timbers?

How come the floor is deemed not strong enough to support habitable requirements, yet handles the header tanks without a problem?

Thanks all.

 

[Static]

Loft will be adequate for normal storage

No, you will need new joists (ie 8x2 or 10x2's) these can be laid parallel to existing ceiling joists.

The water tank will have additional members to support it

If you dont strengthen and you and 4 mates go up into the loft space, with a TV and a sofa, and a fish tank then have a dancing competion, there is a VERY good chance cracks in the plaster will appear along the line of the joists. Ceiling joists are purely designed for storage, ceiling, lighting etc normal day to day habitable useage loads are 3x that.

 

[fatty]

Thanks for that. In my loft, in addition to the joists there are two beams (on top of the joists) running perpendicularly. What are they for?

Thanks.

 

[Static]

Probably its a ceiling binder (provides lateral support to the ceiling joists)

 

[fatty]

So will the loft floor gain strength (or become weaker due to the increased weight) if I run timbers (e.g. 3x2) at 90 degrees to the joists and about 2 feet apart before boarding?