What is the best way to improve loft insulation

pinnks

I did a bit of interwebbing and agree that retail the various boards do require deep pockets! Kingspan seems to be the most expensive and to do 50 of the sq. meters at 100mm would cost, well a lot of hundreds. Indeed, other methods mentioned above may even be cheaper...

Schnee-bay has seconds of all sorts of boards, sizes and thickness for reasonable looking prices but that will require a bit more research.

ed110220

Knauf recommends 100mm of fleece insulation between the joists and then a double layer of Spaceboard to give the recommended insulation value, equivalent to 250 mm of fleece type insulation (or whatever the recommended figure is). I only used a single layer due to the cost as I couldn't justify the extra expense and figured it would be pretty easy to add more at a later date, so it didn't have to be an all in one go job like wall insulation or something like that.

I wouldn't worry about the joists cutting into the boards. It's designed to go straight on top of joists. Ours are technically noggins as they are only about a metre long spanning between steel beams, so they're not as wide as traditional joists. They're about 1.5" wide and I've not noticed any cutting in where I lifted some insulation for the plumbing.

Martyn1981

pinnks wrote: »

What slightly concerns me is the (not quite) point loads on the foam boards where they sit on the joists. Presumably, that is not an issue because if you start approaching that limit you would have so much point weight on that particular board that you risk collapsing the whole roof structure?

When we re-did our kitchen, I decided it was best to dig up the whole floor, which was a clinker type in fill, then put in 100mm of PIR, plus concrete on top.

At first was slightly nervous walking on the sheets, whilst tidying up edges etc, but then realised that they are very strong, and can support loads of weight.

Very poor maths here, which Z can check, but my builder mate weighs about 100kg, so if his boots have a surface area of around 0.03m2, then he must have been placing around 3 tonne/m2 of pressure during each step from the boot on the ground.

There was no damage to the boards.

If you placed a thin ply cover, or thick T&G chipboard, then the point loading would be tiny.

One slight concern though is that ceiling joists aren't really designed for too much weight (assuming you have 75mm to 100mm joists). So the more you make it suitable for storage, the more you'll store, and you could crack ceilings.

We (myself, dad and a carpenter friend) converted my loft, we added 7by2 floor joists. These sat next to the ceiling joists, and rested on the internal and external walls, but packed slightly, so as to make sure they were clear of the ceilings, to prevent any flexing.

Mart.

pinnks

Martyn,

Thanks. My concern about loading was more about the boards resting on relatively narrow joists. Ours are a little smaller than the ubiquitous 4 x 2s, as they of pre-formed truss variety.

I don't have/plan on massive loads up there but do like to spread stuff out to make it more ordered and to spread the loads. 25 years in the ceilings are fine...

I had thought of extending properly into the loft but have not done so for a variety of reasons. I would have done similar to you but had not thought of doing that only to raise the existing floor. Cost-wise it would be similar to laying timber on the existing structure but lad-wise it would all be into the walls. Hmm, food for thought.

On the Spaceboard front, it seems they are no longer available in the UK, other than existing stocks. Anyone know how to source them?

Martyn1981

pinnks wrote: »

Martyn,

Thanks. My concern about loading was more about the boards resting on relatively narrow joists. Ours are a little smaller than the ubiquitous 4 x 2s, as they of pre-formed truss variety.

Not my best explanation.

Flip things upside down, so the joists are now resting on the boards, and the joists represent my beefy builder's boots example, although I suspect with a topping board, your weight and the stored items, will be spread over a greater surface area of joists than one boot.

I may be wrong about this, but a cheaper option might be to fill a load of cheap bin bags (non-biodegradable) with fluffy insulation and cover the floor with them. You can then move them for storage, and the storage itself will help as an insulation since what you are really trying to do is simply trap air. Air is an excellent insulation, so long as you stop it moving around.

Are you too old to play 'forts' and cover your loft in cardboard boxes and bags of 'fluffy' insulation!

Mart.

pinnks

Hi Mart,

Explanation was fine. I think your probably right if the foam boards are that stable. Time for the thinking hat, or at least to look into the empty purse and decide which option to go for. Or maybe just play forts...

ed110220

pinnks wrote: »

Martyn,

Thanks. My concern about loading was more about the boards resting on relatively narrow joists. Ours are a little smaller than the ubiquitous 4 x 2s, as they of pre-formed truss variety.

I don't have/plan on massive loads up there but do like to spread stuff out to make it more ordered and to spread the loads. 25 years in the ceilings are fine...

I had thought of extending properly into the loft but have not done so for a variety of reasons. I would have done similar to you but had not thought of doing that only to raise the existing floor. Cost-wise it would be similar to laying timber on the existing structure but lad-wise it would all be into the walls. Hmm, food for thought.

On the Spaceboard front, it seems they are no longer available in the UK, other than existing stocks. Anyone know how to source them?

That's a pain to hear that they're discontinued as I was planning to board a bit more of the loft, but I'm sure pretty much any insulation board apart from the soft polystyrene types would be OK.

Ours rest on noggins only 1.5" wide so you don't need to worry about it cutting into them.

Ed

EricMears

ed110220 wrote: »

I'm sure pretty much any insulation board apart from the soft polystyrene types would be OK.

Even soft polystyrene would be fine if you can cover them with a sheet of thin plywood (or very thick plywood if you intend to walk around on stiletto heels in your loft )

Martyn1981

EricMears wrote: »

Even soft polystyrene would be fine if you can cover them with a sheet of thin plywood (or very thick plywood if you intend to walk around on stiletto heels in your loft )

I haven't yet gone through!

Lord Morgan: "What a man chooses to do in the privacy of his own attic is his business alone."

Alan Partridge show.

Mart.

ed110220

EricMears wrote: »

Even soft polystyrene would be fine if you can cover them with a sheet of thin plywood (or very thick plywood if you intend to walk around on stiletto heels in your loft )

Hi, I mean ordinary polystyrene may compress too much on the underside against the joists. Whatever type of insulation board you use, you need to put chipboard or some other deck on top if you don't want to fall through it!