I am auditing the loft in my detached 1950s house. I have a list of jobs to do, and some questions have arisen that I would like to resolve before continuing.

Context: when we moved in September '13, in the main part of the loft, there was no loft insulation but the loft was boarded. It appears that at one time the loft was used to live in; the roof itself is boarded and has insulation above the board (I would assume between the rafters). So to an extent the main part of the loft over the centre of the house could be considered "warm".

However there is open access to substantial extensions (I'd guess they double the floor area) that are cold roof. Therefore I surmised it would be best to lay mineral wool insulation on the floor of the loft.

We were in a rush with this project for numerous reasons. I made the decision to get a local guy to lay it on the boards. I regret this now; although he did a good job there is just too many compromises here and there.

So this leads me to a "loft audit" of a number of items, with a number of jobs to do.

The photo attached to this post shows some context. You can see the boarding on the roof, and the boarding on the joists on which the loft roll was sitting (now removed).

I shall add separate posts for each question so the photos can be grouped with the question easily.

Ok, first question and currently the biggest hold up.

Should I remove the boarding on the roof?

The main reason to do this as I see it is to allow more space at the eaves to fit insulation. See attached picture. I can't properly get behind that joist to fit insulation. Thermal imaging showed this as a weak spot.

I don't actually understand how the loft is ventilated. There're no ventilation holes in the soffits. But there's a right gale blowing through the boards, so is it ventilated there somehow?

I think I need to remove this boarding but I want to check before I do anything dumb.

I would, any insulation above them cant be doing much good if there are draughts getting into the loft!

It is illegal to live in a loft and where I am there are big fines available for insulating the roof and putting in a floor in a loft.

they look like quite big ceiling joists

My favourite one this next one!

I performed a thermal imaging survey in January and this popped right up - an open cavity. The one in the image is where an old gable has been extended onto, lengthening the house, then an other extension at a right angle enveloping the old roof.

The old sarking is peeling off and you can see right down the wall. I almost dropped my camera down there!

The same goes for the wall at a right angle to this one, also enveloped by the second extension I mentioned.

What to do? Get the CWI people out, will they fill internal walls?

Does the style of block with horizontal lines have a name btw?

Hollow tile blocks, very brittle and now made of terracotta and more common in Europe.

I would tip polystyrene beads down the open cavities.

I would seal the joists where they go into the walls.

<blockquote><cite>Posted By: gravelld</cite>I don't actually understand how the loft is ventilated. There're no ventilation holes in the soffits. But there's a right gale blowing through the boards, so is it ventilated there somehow?
</blockquote>
Is there felt/membrane in the roof? If not, air will flow freely between the tiles. Unless the boarding and insulation were designed to be airtight, you could expect some ventilation by that route.

I don't see any great need to remove the boards unless they interfere with your other plans. However, I would be tempted to take off one board, or cut away as much as you need, to see what's actually going on up there. That might help you to decide whether the boards are really preventing you doing a proper loft insulation job.

We inherited a loft with plasterboard fixed to the rafters and glassfibre or rockwool insulation above. I had to cut away the bottom ~300mm of plasterboard to instal new ceiling joists. That also meant I could push the new insulation right out to the tiles. I left the old insulation and most of the PB in place and the loft is now surprisingly warm despite >200 mm of insulation below it.

Peeps, I don't want to mess up on the ventilation here.

Can someone suggest how the loft is currently ventilated? There are no soffit vents.

The roof is boarded and insulated, and I feel a draught coming through the joins in the board.

How does the ventilation work?

Do I stand a chance of blocking the ventilation if I remove the boards and insulate as far as possible into the eaves (up to the inner leaf of brick)?

Thanks Tony.

I don't have any sheet insulation but assume it'll be ok with loft roll. Worth buying rafter trays to ensure the gap?

Actually I need to buy some rigid insulation anyway. Which sheet material?

I need to take the roof boards down to see what I can fit in, i.e. what the clearance above the joists is.

Do I cut to size then fill the gaps to joists/inner leaf with foam?

I poured bead into hard to reach places with a length of waste pipe (40mm I think) - it worked quite well, you don't need much of a slope to get them to flow. Can redistribute them by pushing around, gets over the triangle problem quite well. I did also use a bunged up bit of 32mm to push the beads out when then wouldn't flow...

What's the comparative R of loose fill bead versus EPS sheets?

Any reason not to use PUR? Financial expense?

As above I have some open cavities Tony has suggested filling with bead.

Best (probably cheapest) source?

Thanks.

To add to the final point, I shoved the camera in as far as it could go and took this picture. Assume this is the external wall in the foreground. I'm confused though, looks like there's a joist gone all the way through it and there's plasterboard outboard?

Help understanding that picture is gratefully received.

I'll try to move the short bit of joist to test that...

Will try bead, difficult to get "over" the joist with a vessel containing loose fill. Will see what I can do, need to buy bead for the cavities anyway.

Can you confirm where the wall plate is here? Will it just be sitting on the inner leaf or does it bridge the cavity and rest on the outer too? As you can see from the previous picture the top of some masonry is exposed. I tried to feel down around the masonry but could not find a cavity nor insulation.

Soffits are timber, at least from the outside!

So using the EPS as a rigid sheet to ensure the ventilation gap? Not concerned about crushing the loft roll underneath?