Victorian mid terrace loft and central joist support

[Builder2011]

Good evening. My loft has been packed for years with heavy boxes on miscellaneous boards across the joists. I have now got a moment to strengthen the joists and put down some proper boards. The building is about 7m from front to back and about 4.6m across and is a Victorian mid terrace building on ground and first floor.

The existing loft joists are 3.6m from front to middle resting on a 4" x4" across joist from party wall to party wall, and then 4.2m from the middle to the rear. They are 4" x 2".

The across joist from party wall to party wall is a 4" x 4". It has two 1 1/4" inch round holes cut in towards the middle for wires. Through the holes I see that the wall below (first floor middle across wall) is not a solid wall (or that part of the wall that I can see).

So if the wall below is not load bearing, how is the 4" x 4" across joist holding up all the loft joists? And can a 4" x 4" joist from Victorian construction really span 4.6m, and if so how has it held up so many heavy boxes for so many years?

The middle across wall has one door way. On the upright side of the door nearest the middle of the building the wall does seem to be solid for about 4". Could there be a support there? Are there any drawings available for this type of Victorian construction?

 

[alfiembra]

How long is a piece of string?

It's difficult from your description to really get a clear picture of how the 4x4 is supported, but thoeretically it would be difficult to prove it could span 4.6m all in one clear span by today's standards. That being said it obviously is doing the job so it would be logical to assume that there are other supporting walls at some point along the length of the 4x4 that are breaking it up into smaller spans. These could be dividing walls between rooms running perpendicular to the 4x4 and providing a support at the points where they cross.

As for drawings go to your local council building control offices and enquire if they have any original plans for your address you'll be surprised what they have in their archives.

HTH

Alan