Is my loft strong enough?

[Andrew Reid]

Hi All,

I'm in the process of laying some boarding in my loft, primarily for storage purposes of small light boxes, however I am thinking long term and ideally would like to use this a bit more for setting up a model railway. I'm looking for some general advice on if the loft flooring would be able to bare weight on it for a couple of hours every few days to that regard. Currently, I have removed a layer of insulation in order to avoid crushing this down so that the 1st layer is inline with the height of the joists and I have placed chipboard panels (https://www.diy.com/departments/chi...k-of-3-l-1220mm-w-325mm-t-18mm/1673191_BQ.prd) across the joists ensuring, that these finish in the middle of a joist and the ends do not 'float' without any support. For the insulation I have removed, I am going to replace this in the roof above with some foam insulation panels.

In terms of the joists, the spacing between these is 56.5cm. Each joist is 3.4cm in width and 7cm in height. I've attached a picture of work to date. Is the current method sufficent for my future requirements or would further re-enforcement be needed later down the line? If there is a calcuation of how much weight there can be per meter square that would be useful as well. I'm not the lightest of people and very much aware that any weight needs to be distributed as equally as possible across the existing joists.

Kind Regards,
Andrew

 

[johnny2007]

What's the max span of joists?

 

[Andrew Reid]

What's the max span of joists?

When you say max span, do you mean from one end of the joist to the other (i'm not well acquainted with terminology for loft matters). If thats the case, I don't have an exact measurement, but its approx 544cm

 

[johnny2007]

That's a lot.
There must be another support somewhere in the middle.
Any supporting wall or beam?

 

[Andrew Reid]

From what I can see so far up there, no other supporting beams. The only thing I can see (and in the last photo posted above) is the beams of wood which are running parrallel outside of the boards I have placed. They are ontop of the joists though and not underneath them. If its any help, the distance between those is approx 180cm. The bathroom is directly underneath that space so perhaps the walls of the bathroom play a part in the support here? The V beams look like they MAY run parallell with the bathroom walls but its tricky to judge.

 

[johnny2007]

Yes, there must be something else holding those joists.

 

[Andrew Reid]

OK thanks, i'll see if I can dig around a bit more tomorrow to find them. Speaking purely in hypotheticals, if it turns out there is a support every 180cm for the joists, how would that sway your thoughts?

 

[johnny2007]

To be honest even at 180cm span I would want something bigger than a 3inch joist.
I go by experience, here there are engineers who will give you better details about what's required.

 

[Andrew Reid]

Thanks, appreciate the input

 

[Leofric]

They are gang nailed prefabricated fink trusses and the ceiling ties basically hang from the gang nail plates joining the timbers together when you turn them into floor joists by boarding out . You have reduced the insulation thickness by putting chipboard on top of the existing joists/ceiling ties so that isn't good . This sort of thing might be ok for a small area for maintenance around the cold water tank in the loft but I would be looking for a better solution for your hobby. The boards you mention are longitudinal bracing but 70 x 34mm joists are too small as floor joists for a span of about 1.8m. How much loading can gang nail plates take ,maybe others can answer that