Hello GBF,

We live in a 60s semi in north oxfordshire and are soon to be removing the (dreaded) finlock gutters on the property due to ingress of water the junction with the adjoining house (which had the gutters removed 7 years ago or so). A couple of things have come up in my research.

Firstly, I have only just realised that there is possibly a vent from concrete gutter block into the cavity (this would be in the section within the roof area i.e. not the water-carrying-gutter section). Would it be sensible to get the contractor to squirt in a bit of expanding foam into any cavity vents that are revealed? The cavity was filled in 2012 with what I think is knauf supafil (I have seen the certificate somewhere but not recently!).

Secondly, what would be the best strategy to insulate the eaves area? I am not sure of the final clearance to the eaves support trays that will be installed in the works, so my idea would be to buy some 20mm sheets of PIR and sequentially slide these into the eaves area to form a sandwiched wedge of insulation that closely conforms to the eaves trays but maintains airflow into the roof (with little wastage of material since no diagonal slices need to be made into thicker sheets). In effect I would end up with a boundary wedge of PIR that spans 50cm to 1m(?) of the eaves zone before loft roll takes over where the headroom to the rafters opens up. This approach would be similar to the Roof Insulation to Eaves detail as described in the Retroft Pattern Book (https://retrofit.support/detail/50/).

Thirdly, since we are not in a position to EWI the property (which I would love to do but have a forced hand due to the leaking issue), is there any value in asking the contractor to fix a thin sheet of insulation beneath the soffits? I imagine the cut edge to be pretty rough would question the insulative properties of ill-fitting 25mm PIR (for example) on such a surface.

Any advice is gratefully received...I am long time "listener" (like 13 years!), first time caller and just a home owner with an interest in retrofit and no serious DIY skills.

Cheers,
DarthGarth

Thanks Tony. That is definitely one of my aims but I am yet to see the detail around the rafters and finlock blocks to know how much overlap I can achieve. I will have a look when the scaffold is up or get the roofers to take some pics when they are working.

If I dropped, ever so quietly, the fact that I bought (and read) your (very informative) Draughtproofing & Insulation book could that persuade you do comment on any of the specific details of my insulation strategy?

Appreciate the reminder working in the eaves from the inside, Philedge. I will contact my roofer and see what their intentions were regarding restoring the insulation after the gutter removal and build up of the eaves.

I have signed up with a Retrofit Pattern Book account so I can now see the full labelled diagram. I can also see that I had got some wires crossed about what was quilt and where the sheet insulation was fitted in the image.

Whilst I dont think it'll be possible to directly replicate due to the relative positions of the rafters, eaves support trays, wall plate etc with the finlock set-up, I will see if they are willing to install additional battens along the rafters and fix sheets of PIR beneath the battens as to maintain the air gap from the eaves vents to a height of about 40cm. I can then stuff quilt into the wedge beneath and hopefully be as continuous as possible with the cavity fill and give scope to layer on a load more quilt.