Boarding Loft - Insulation Advice & Pinning

[rossbardon]

So, there is a lot of usual info on this thread with all the helpful responses I've received. So I will post some updates and photos on my progress as this may aid somebody else in the future.

Today I cleared out all the old rubbish and the top layer of my insulation (which had been churned up due to a recent replacement of my heating system and my old out dated electrics). Here is the loft 'after' the clean up.

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• rossbardon
• 3 Mar 2012
• 1

I decided to leave the first layer of insulation down for the following reasons;

1) it is very old and very dusty (the black you see is dust not mould, its bone dry).
2) I found a label which states this insulation is 'slagbestos' mineral wall. A quick google and I have only found information to state 'slagbestos' does not contain asbestos, but it not worth the risk is it. Its old insulation 1930-1940's!
3) This old slagbestos insulation has a black paper barrier layer on the underside (in 90% of places anyway). This will suffice as my vapour barrier for the loft?

Please if anyone disagrees with any of those arguments above, then please say if you think it is worth me replacing this original layer of insulation.

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• rossbardon
• 3 Mar 2012
• 1

Tomorrow I will 'top up' this insulation to bring it flush with the joist. I am planning on using this insulation. Sound ok?

http://www.diy.com/nav/build/insula...ooselay-Loft-Insulation-11837506#BVRRWidgetID

 

[rossbardon]

Hi,

Slow progress on Sunday! We spent most of the day crawling along the loft clearing out the eaves. Once this was done we started to top up the base layer of insulation as shown in the image below.

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• rossbardon
• 5 Mar 2012
• 1

The socket wiring (you can see in the socket in the image) has been run along a joist, and covered in 25mm steel conduit. There are no shower cables in my loft.

The next job is to lay the perpendicular joists down (to raise the floor and provide more space for another 100mm insulation). I'm planning on connecting the joists to the existing joist using simple 2.5 inch angle brackets. These are not heavy duty but they should stop the joists moving / twisting.

Next question, 406mm centres or 606mm centres? I just cannot helping thinking the 406mm centres is excessive (I'll need a lot of joists). Is 406mm centre spacing not the required spacing for a living floor? Will 606mm centres using 18mm chipoard be sufficient for a loft storage area? Anyone ever taken this option or is it a no go?

 

[freddiemercurystwin]

600 will be fine for loft storage.

 

[rossbardon]

Ok, the materials have arrived. I am hoping to get through the job in one weekend. But, a last minute concern.

I've been told I should not be laying my 'raising' joists perpendicular to the existing joists. Instead I should be gluing and screwing the new joists on top of the existing joists as this will add strength were as going perpendicular with the joist will not add any strength.....

Hmm what should I do?

 

[JohnD]

your friend is probably thinking of beam depth. It is true that if you could laminate the timbers so securely, over their entire length with no notches, gaps or cutouts, they would be stronger and more rigid. However I don't know that you will be able to laminate them into a single member to this standard

The idea of cross-battening is that your weight will be spread over several of the old timbers. When they are all screwed together and the deck is firmly fixed, it will be quite a lot more rigid.

 

[rossbardon]

Yeah I see what you mean, going perpendicular will improve weight distribution but not really overall strength of each beam.

Laminate will improve each timber strength but loads will still be isolated loading.

So its 6 of one half a dozen of another?

I will stick with the perpendicular idea then. How would you recommend I pin the perpendicular joist, floating on the current joists (no need to fix to walls?) and counter bore and drill down into existing joists? Screw size?

I was going to do use simple angle bracket but maybe it would be better to fix laterally, rather then using cheap angle brackets?

 

[freddiemercurystwin]

No you're friend is wrong in this sitauation perpendicular is much better.

Fixing a batten on top of a joist does not turn it into a deeper beam depth overall in terms of its structural integrity unless they are attached in such a way as to make one homogonus element and this can only be undertaken by pursuing a meticulous procedure of milling, gluing, compressing, screwing etc etc etc.

No need for any angle brackets either frankly just screws in on the skew where ever they connect, maybe add a row or two of noggins if you're that bothered, in anycase once the chipboard is screwed down it will all keep things rigid OK. You're adding a deck for storage not making a structural floor.

 

[rossbardon]

Hi,

Sorry for the lack of updates.

So far, I have laid and fitted the perpendicular joist to the ceiling joists. Before I start to lay the boards I wanted to find a bit more out about the construction of the ceiling joists...


It appears that there are long joists running from the front of the house to the centre of the building. Like wise there are also joists running from the back of the house also to the centre of the building. There is a small overlapping section (maybe 1 foot) of these joists as the ones from from back to centre meet the ones coming from front to centre. At the centre of the building these joist are overlapping and are sitting on top of the dividing walls between the upstairs bedrooms. It just got me wondering what is restraining these joists at the centre point? Why are they not pivoting upwards as at the opposing end these joists are under the loading of the roof but in the centre there no longitudinal load? Please see the photo. This is the particular section in the centre of the building wear the joists overlap which I am keen to understand better.

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• rossbardon
• 22 Mar 2012
• 1