Advice for insulating and boarding old bungalow loft (2x4 joists)

elsmandino

Hi there.

I am thinking of properly doing my loft up (at last) but would be really grateful for some initial advice.

It is a 1930s bungalow with 2x4 joists.

There are patchy bits of fibreglass in areas and other parts filled with vermiculite - there are various bits of boards in parts and areas which are just bare.

I am thinking of just putting down fresh fibreglass everywhere and then putting some interlocking chipboard loftboards over the top.

The current regulations seem to suggest that 270mm is the norm, which is not really going to be an option for me.

Further, you apparently need a 50mm airgap between the top of the insulation and the top of the loft board.

Any advice on what to do would be much appreciated.

My initial thought is to run some (2x2, or even 2x2) timbers perpendicular to the current joists and just put some 100mm insulation down - seems the best I can do, but allows the airgap as well. Can then fix the loftboard to the new timber on top.

kipsterno1

Have you considered using something like this? 

https://www.diy.com/departments/diall-loft-storage-stilt-pack-of-12/3663602538240_BQ.prd

I used them when I boarded part of my loft space. Found them simple to install.

elsmandino

I did actually consider those but my research suggested that you have to be a bit careful using them (especially if you have small joist, like I have).  Seemed to be an issue with concentrating the load on a smaller area (which could lead to sagging).

FreeBear

elsmandino said:

I did actually consider those but my research suggested that you have to be a bit careful using them (especially if you have small joist, like I have).  Seemed to be an issue with concentrating the load on a smaller area (which could lead to sagging).

Have 3x2 (75mm x 50mm) joists spanning 4m in my loft. No problems with using loft legs or sagging timbers. Spread the load, don't store vast weight up there, and you'll be fine.

MisterNick

I'm in the process of insulating my loft at the moment. I am removing all the old insulation and hoovering all the muck out. 
I have used these 
https://www.celticsustainables.co.uk/loft-legs-for-raised-loft-floor-175mm-box-of-12/
with these screws 
https://www.celticsustainables.co.uk/multi-purpose-screws-ideal-for-loft-legs-200-box/
to elevate the boards. reasonably easy to fit, but I did put the screws in place in the bases.

I used these to cover the lights in the bathroom, not sure if I had to, but used them anyway
https://www.lbsbmonline.co.uk/loft-lid-downlight-cover

I used this insulation between the joists 
https://www.diy.com/departments/knauf-eko-roll-loft-insulation-roll-l-7-28m-w-1-14m-t-100mm/182146_BQ.prd

and this over the top
https://www.diy.com/departments/knauf-eko-roll-loft-insulation-roll-l-5-68m-w-1-14m-t-170mm/663953_BQ.prd

These rolls come in 1.2m bales but seem to have incisions at 400mm and 600mm which make it really easy to cut to size for between the joists. In your case you would get three lengths out of the width.

I already have 2.4m x 600mm chipboard which I am reusing.

In no way could I be considered an advanced DIYer, but I am finding it relatively easy, but a real faff because of the dust and workspace.I've got one section done and expect to speed up for the next sections.

elsmandino

Thanks ever so much for this.

It did just occur to me that, if I put some perpendicular joist across, this would be no difference to loft legs as the point of contact would just be the same.

I think I am going to do exactly what MisterNick is doing.

One quick thing, with regard to the actual boards themselves - 

Are the interlocking boards the best way to go?

Chipboard Loft panel (L)1.22m (W)0.33m (T)18mm , Pack of 3 4900g | DIY at B&Q

The obvious advantage of these is that, as they are interlocking, they will strengthen each other.

However, aren't these a bit problematic if you need to lift up a loft panel for maintenance purposes (i.e. you need to pull them all up, to one side, to get to it)?

FreeBear

elsmandino said: However, aren't these [T&G boards] a bit problematic if you need to lift up a loft panel for maintenance purposes (i.e. you need to pull them all up, to one side, to get to it)?

You either plan the layout so that you only need to lift a minimum of boards, or cut the boards at strategic points. Aside for lighting cables, there is very little in a typical loft that would need maintenance.

Bendy_House

Perp joists is fine, but surely both heavier and more costly than legs?

Yes, T&G panels are stronger at the edges, which is very useful where they don't happen to align with the joists below - which they likely won't without wasteful cutting. But, yes, to subsequently lift a panel will require the tongue to be cut through. Annoying, but not the end of the world. To refit will likely need a batten or similar to be fitted along the hole's perimeter, on its underside, to provide a narrow frame for the removed panel to then just pop back down, easy to lift in future.

elsmandino

Perfect - thanks very much.  Going to crack on with this, before the winter starts.

One further thing, out of interest really - 

I note that I could get away with 100mm of insulation, only - i.e. after that, the saving to thickness ratio starts to decline quite rapidly.

Purely from a selling perspective, would 100mm be off-putting for perspective buyers or do they all want 270mm now?

FreeBear

elsmandino said: I note that I could get away with 100mm of insulation, only - i.e. after that, the saving to thickness ratio starts to decline quite rapidly.

Purely from a selling perspective, would 100mm be off-putting for perspective buyers or do they all want 270mm now?

100mm is the bare minimum. You will lose a point or two on your EPC, and it could put some buyers off. A few rolls of insulation is not that expensive, and the more energy you can save, the better your bank balance.