How much can I safely store in my loft?

[vcps2021]

Hello,

I'm not sure if anyone can help me with this...

I have moved into a 20 year old property with a decent sized loft space that's already been boarded with chipboard (and insulated) and I'm trying to find out what weight the floor can take per square metre?

The joists are 60cm apart on centre and are 4.5cm wide by 9.5 cm high.

I'm not planning to push it close to the maximum and I'll spread it out as much as possible - just wanted to get an idea of it's rating so I can feel reassured that I'm pretty far away from it.

Thanks for reading!

[wozza]

I would be interested in any answers to this as I am considering doing the opposite.

 

I have lived in my house for 20 years, I want to remove everything form the loft, remove the boards and insulate to a good depth. - My trusses are of a similar size.

 

[Ferdinand]

29 minutes ago, wozza said:

I would be interested in any answers to this as I am considering doing the opposite.

 

I have lived in my house for 20 years, I want to remove everything form the loft, remove the boards and insulate to a good depth. - My trusses are of a similar size.

 

 

What is the weight of the things you currently have stored in your loft? And the area?

 

@vcps2021 this amount should be OK ? .

[Ferdinand]

36 minutes ago, vcps2021 said:

Hello,

I'm not sure if anyone can help me with this...

I have moved into a 20 year old property with a decent sized loft space that's already been boarded with chipboard (and insulated) and I'm trying to find out what weight the floor can take per square metre?

The joists are 60cm apart on centre and are 4.5cm wide by 9.5 cm high.

I'm not planning to push it close to the maximum and I'll spread it out as much as possible - just wanted to get an idea of it's rating so I can feel reassured that I'm pretty far away from it.

Thanks for reading!

 

More seriously, trusses are designed to tight tolerances, so not too much. Your in situ beams may be labelled on the beam.

 

Also, are they supported by an intermediate wall part way along, for example?

 

But I don't see anyone taking a tonne of barbells up a loft ladder.

 

 

[vcps2021]

Hello and thanks for your answers....

 

I have 140kg of stuff spread over about 5 positions.

 

My flat is meant to be 45sqm so the loft is roughly the same, It's more long and thin with the longest dimension of the flat being 11.5 metres and varying widths.

 

The actual beams are boarded over and insulated - I recall seeing some writing on the trusses but it was more about the plot number the truss was intended for - I'll take another look to see if there are further clues.

[markc]

Hi, 140kgs is nothing.

4x2 bottom cords are quite big for trusses so you are already at an advantage.

I would have no problem with loading 45sq metres with 1000kgs distributed.

Please remember to take the weight of boarding into account even though these add stiffness and help distribute the load

Edited September 6, 2021 by markc

[markc]

If you have any photos these would help as trusses have different load bearing capabilities depending on design and especially if they sit on walls or free span

[vcps2021]

That's good to hear - would like to put more up but realistically should't be anywhere close to 1000kg!

 

I pulled up some of the insulation in an unboarded section so you can see how that looks.....

 

 

here the strip of wood towards the bottom of the image (under the white wire) corresponds with some wall

 

 

here are some of the trusses with info on them...

 

 

 

 

 

 

Thanks again for taking a look!

 

 

 

[George]

Lofts aren't supposed to be storage spaces but if you stick to 60kg / sqm, you're unlikely to have any issues. 

 

 

[Gus Potter]

Hello all.

 

Hope this helps give you some pointers for typical fink trusses, attic storage and what extra load you can put up there.

 

 

The truss manufacturers often design to BS 6399 loadings unless told otherwise. Below is a typical example of the ceiling loads for an uninhabited attic.

 

 

Roughly to convert N (Newtons) to kg you divide by 10. Thus an imposed load of 250 N/m^2 is 250/10 ~ 25kg per square metre. An imposed load can be your holiday stuff, hats and sun cream, or xmas decorations.. basically stuff that can get moved about and remember that you have to hold a heavy suitcase so there is you body weight to add.

 

Now once you add in the weight of the chipboard flooring say 12 - 15 kg /m^2 = say 100 to 150 N/m^2 you are left with only being able to put about 10 to 15 kg of stuff up in the attic all spread out. Naw! really? You may ask.. I'm 15 stones (about 100kg ~ 1000 Newtons) so why does the ceiling not collapse when I go in the loft?

 

Simplistically prefabricated trusses are designed to be as economic as possible. The truss manufacturers take advantage of the properties of timber which are different from steel. One key thing about timber is that is can carry a short term "shock load" like you at 15 stone without breaking. This is shown above as 900N ~ = 90 kg. You'll see an allowance of 75% for load sharing. This recognises that often you won't put all you weight on one bit of timber for any length of time and that there will be noggings (dwangs) and so on that shed some of the load to the adjacent timbers.

 

But when a timber is loaded over a long time it starts to creep and is less able to sustain long term stresses, it is after all mostly celulose. You can see this in say old roofs that have sagged. This will also happen to your ceiling and can manifest in cracks. Also, as the timbers sag too much they can introduce other unwanted forces into the small nail plates (called second order effects) and they will "protest".

 

Sometimes you can add a bit more load locally if you have some "load bearing" walls below, but let's be cautious for now.

 

I'm not saying you can't start using your trussed rafter roof to carry extra load. There are a few ways you can simply strengthen some of these roofs. There is a temptation to start using the space more regularly, put electrical sockets in, maybe a bit of insulation. When you come to sell the Surveyor says.. hold on where are the permissions and calcs for all this. If you are going to put a more solid floor in please bear in in mind the above and make sure you can easily strip it all back out if need be. Please do not cut any trusses as this falls under BC regs and the scope of a building warrant in Scotland.

 

One other point to bear in mind is this. While all may seem fine to begin with if you start pushing your luck and eating into the safety factors that were used in the truss design then you could get a serious failure when we get a big snow fall. It could be xmas time with a house full of kids!

 

In summary if you have any doubt get an SE in, even if it is to reassure. Then enjoy your additional space.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[vcps2021]

Hi Gus - thanks for your detailed post. Just one quick question to clarify....when you said:

 

Quote

Now once you add in the weight of the chipboard flooring say 12 - 15 kg /m^2 = say 100 to 150 N/m^2 you are left with only being able to put about 10 to 15 kg of stuff up in the attic all spread out. Naw! really? You may ask.. I'm 15 stones (about 100kg ~ 1000 Newtons) so why does the ceiling not collapse when I go in the loft?

 

Did you mean, I can have 10 to 15 kg of stuff per square metre? I'm pretty sure that's what you meant but I don't wish to be guilty of "hearing what I want to hear"!

A SE did visit the property for another purpose and happened to mention the loft was rated to 25kg/sqm in passing. From what I have read and understood since, I found that 18mm chipboard weighed 11.7 - 12.4 kg/sqm and thought having 10kg of stuff per square metre ie 400kg (well spread) would be sufficiently cautious.

From what you've said, I think we're on the same page?

 

Thanks again!

 

[Gus Potter]

4 hours ago, vcps2021 said:

Hi Gus - thanks for your detailed post. Just one quick question to clarify....when you said:

 

 

Did you mean, I can have 10 to 15 kg of stuff per square metre? I'm pretty sure that's what you meant but I don't wish to be guilty of "hearing what I want to hear"!

A SE did visit the property for another purpose and happened to mention the loft was rated to 25kg/sqm in passing. From what I have read and understood since, I found that 18mm chipboard weighed 11.7 - 12.4 kg/sqm and thought having 10kg of stuff per square metre ie 400kg (well spread) would be sufficiently cautious.

From what you've said, I think we're on the same page?

 

Thanks again!

 

Yes looks like on the same page. The 25 kg per square metre your SE mentioned is shown in the "Ceiling Tie loads screen" shot as "Imposed load (loft storage)  250 N/m^2. Off this you deduct flooring weight to arrive at the figure of ~ 10 kg per square metre.