Loft insulation, squished or not squished?

Section62

ohdarn said:

I'm not concerned about the joists carrying the weight as I've been up there working on them but I would be concerned about chipboard perched on top of legs, supported in less places than if they were laid on joists, when I know there's up to a six metre drop below me if something fails.
And I don't want to raise the electrics further to make them accessible.
In short, I ain't using loft legs.

If the loft legs failed then the boards would land on the joists, leaving you more or less in the same position as if the boards were laid directly onto the joists as you plan to do.  There's not really much difference.

Although you say you "weigh a considerable amount", when you were working in the loft you were acting more or less as a point load and (presumably) moving around very carefully.

The structure of lofts is typically designed to support the ceiling below, the forces from the roof structure, and to cope with a point load from someone working in the space.

The principal issue with most loft storage conversions is the cumulative load being added - you may feel you weigh a considerable amount, but you are a lightweight in comparison to the total mass of the boards and 'stuff' being installed and stored. 18mm chipboard is darn heavy, and although distributed over the area of the loft, it adds up to a lot of additional mass for the structure to deal with.

Mutton_Geoff

ohdarn said:

And either option will mean having to extend the electrics so they're not buried under the insulation.

What's wrong with cables under insulation?

ohdarn

Section62 said:

ohdarn said:

I'm not concerned about the joists carrying the weight as I've been up there working on them but I would be concerned about chipboard perched on top of legs, supported in less places than if they were laid on joists, when I know there's up to a six metre drop below me if something fails.
And I don't want to raise the electrics further to make them accessible.
In short, I ain't using loft legs.

If the loft legs failed then the boards would land on the joists, leaving you more or less in the same position as if the boards were laid directly onto the joists as you plan to do.  There's not really much difference.

Although you say you "weigh a considerable amount", when you were working in the loft you were acting more or less as a point load and (presumably) moving around very carefully.

The structure of lofts is typically designed to support the ceiling below, the forces from the roof structure, and to cope with a point load from someone working in the space.

The principal issue with most loft storage conversions is the cumulative load being added - you may feel you weigh a considerable amount, but you are a lightweight in comparison to the total mass of the boards and 'stuff' being installed and stored. 18mm chipboard is darn heavy, and although distributed over the area of the loft, it adds up to a lot of additional mass for the structure to deal with.

Loft legs is not what this thread is about, I ain't using them, I'm not bothered about people's opinions of them.
I'm not responding to anymore posts about them.

ohdarn

Mutton_Geoff said:

ohdarn said:

And either option will mean having to extend the electrics so they're not buried under the insulation.

What's wrong with cables under insulation?

I like to be able to easily access such things. I don't want to be moving storage items, boarding and insulation to be able to access them if I need to.
There's a good chance as we renovate the house, that we will need to access them and see where they run.
I'm not sure what this has to do with the insulating properties of squished or unsquished loft insulation though?

Section62

ohdarn said:

Section62 said:

ohdarn said:

I'm not concerned about the joists carrying the weight as I've been up there working on them but I would be concerned about chipboard perched on top of legs, supported in less places than if they were laid on joists, when I know there's up to a six metre drop below me if something fails.
And I don't want to raise the electrics further to make them accessible.
In short, I ain't using loft legs.

If the loft legs failed then the boards would land on the joists, leaving you more or less in the same position as if the boards were laid directly onto the joists as you plan to do.  There's not really much difference.

Although you say you "weigh a considerable amount", when you were working in the loft you were acting more or less as a point load and (presumably) moving around very carefully.

The structure of lofts is typically designed to support the ceiling below, the forces from the roof structure, and to cope with a point load from someone working in the space.

The principal issue with most loft storage conversions is the cumulative load being added - you may feel you weigh a considerable amount, but you are a lightweight in comparison to the total mass of the boards and 'stuff' being installed and stored. 18mm chipboard is darn heavy, and although distributed over the area of the loft, it adds up to a lot of additional mass for the structure to deal with.

Loft legs is not what this thread is about, I ain't using them, I'm not bothered about people's opinions of them.
I'm not responding to anymore posts about them.

In which case asking "So what would you do?" in your first post was perhaps a bit misleading, and unfair to other forum members taking the time to reply to your question.

In any event, my post was neither 'pro' nor 'anti' loft legs.  Just pointing out for the benefit of all forum users that your logic for not using them isn't based on the facts - i.e. that if you are concerned about them failing then you should be more concerned about overloading the ceiling joists and roof structure.

That's a safety issue which shouldn't be ignored.

ashe

I'd use loft legs 

casper_gutman

Unsquished insulation will be better. The air is the bit that does the insulating.

No comments on loft legs from me, except to wonder what they have to do with covering up the electrics. Wouldn't they be covered up anyway, when the boards go down?

ohdarn

casper_gutman said:

Unsquished insulation will be better. The air is the bit that does the insulating.

No comments on loft legs from me, except to wonder what they have to do with covering up the electrics. Wouldn't they be covered up anyway, when the boards go down?

Thanks, but I've found an American site now that suggests there may be not really much of a  difference after all.

There is enough cable as it is to put the electrics, particularly the junctions, above the boarding as it is.

But since we've not long moved in, we may want to add switches in certain places at a later date (some of the current locations of switches are in odd places) and so would prefer the ceiling/loft floor to remain relatively accessible.

On top of that, we've discovered the 300mm of insulation that was previously fitted has masked pest infestations and roofing leaks that have rotten some structural portions of the roof.

Gunner276

If you are planning to do electrical work involving wires in the loft, do it first.
Then board the loft using the appropriate amount of insulation and loft legs

ohdarn

Gunner276 said:

If you are planning to do electrical work involving wires in the loft, do it first.
Then board the loft using the appropriate amount of insulation and loft legs

No.