Green Building Forum - Insulation to eaves of existing 42º pitched roof and solid walls Wed, 10 Jun 2026 02:50:43 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134603#Comment_134603 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134603#Comment_134603 Thu, 09 Feb 2012 22:33:16 +0000 Shevek Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134605#Comment_134605 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134605#Comment_134605 Thu, 09 Feb 2012 22:44:03 +0000 pmagowan Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134608#Comment_134608 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134608#Comment_134608 Thu, 09 Feb 2012 23:19:39 +0000 Shevek http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=8503

Can't go above rafters because it's mid-terrace. :sad: I'm guessing the air barrier will need to be at the internal lining, yes.]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134615#Comment_134615 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134615#Comment_134615 Fri, 10 Feb 2012 07:23:20 +0000 Mike George http://www.cavitytrays.co.uk/ventilation/view/2/81/1/type-oevwf-open-eaves-ventilator. This will leave you with the thinnest insulation at the wall plate zone. If this still bothers you create an insulated skeiling between the flat ceiling and the wall]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134620#Comment_134620 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134620#Comment_134620 Fri, 10 Feb 2012 08:33:46 +0000 Shevek
The problem with standard ventilators like that is that they require fitting from above the rafters. Is it possible to take just the lower first half dozen runs of roof tiles off? If so perhaps I could use a couple of runs of this product:
http://www.cavitytrays.co.uk/ventilation/view/2/78/2/type-erov-eaves-roll-out-ventilator]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134621#Comment_134621 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134621#Comment_134621 Fri, 10 Feb 2012 09:00:15 +0000 jamesingram Posted By: ShevekThe problem with standard ventilators like that is that they require fitting from above the rafters. Is it possible to take just the lower first few runs of roof tiles off?
?

Hi , did this yesterday to a place . easy with a tower ,

take the first 3 rows of tiles off , tuck quilt under rafter and against wall at soffit and to meet up with loft quilt.
Cut PUR 800mm long to fit inbetween rafters , push in so as bottom of PUR joins up with EWI or just over wall
if your EWI in the future . replace with breather felt/batton etc , stick 10mm nail-on vents along top of fascia

I've left a 25mm gap above PUR , large rafter 75mm gap at plate junction, so used 50mm pur

slightly different to you as you converting the loft , but with the tile off you can join up the VB and connect
ewi and internal loft pitch insulation

on my own place i used 50mm and have no vent gap as im not concerned re. condensation over this short length as I've a good VB for wall to ceiling connection and cold vented loft]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134622#Comment_134622 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134622#Comment_134622 Fri, 10 Feb 2012 09:02:50 +0000 jamesingram
or you could attack from above, inside , without moving tiles , some info here http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=6190&page=1]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134626#Comment_134626 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134626#Comment_134626 Fri, 10 Feb 2012 09:18:15 +0000 jamesingram http://www.screwfix.com/p/over-fascia-ventilator-10mm-x-1m-pack-of-10/65515

nail on over fascia vents]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134680#Comment_134680 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134680#Comment_134680 Fri, 10 Feb 2012 13:41:31 +0000 Shevek
Won't building control insist on a 50 mm gap in accordance with BS 5250? Or is it different for existing buildings?

I'm not sure that the vent over fascia would work because it's a mid-terrace house so I can't adjust the height of the guttering or roof tiles.

Why do you recommend PUR as opposed to PIR? What about Aerogel?

I've also been wondering about lowering the joists. Only problem is we need to live in the place while we're doing it.]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134703#Comment_134703 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134703#Comment_134703 Fri, 10 Feb 2012 14:53:40 +0000 jamesingram
As far as i'm aware B.regs require 25mm cont. air gap , most leave 50mm between rafter with old style felt to make up for rafters ?? you could argue with the correct breather felt no need for any airgap, though most require 25mm.

the 10mm height increase wont show in anyway relative to ajoining terrace , just a slight lift in the tile at either end. unnoticable from the ground.

PUR/PIR it's all the same to me , celotex,xtratherm,kingspan:bigsmile:
you could use aerogel as it's a small gap you may have to work with. never used it , not sure of ease of supply.
how about phenolic

Lower joist to increase loft space is quiet common . do this first, fit joists, tack out ceilings
then work, doing rip out, from above via scaffold/roofwindow (or loft hatch) , drop in stairs last and skim ceiling over when completed loft . bit of a mess but keeps the first floor liveable]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134740#Comment_134740 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=134740#Comment_134740 Fri, 10 Feb 2012 19:00:25 +0000 Shevek Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135013#Comment_135013 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135013#Comment_135013 Mon, 13 Feb 2012 10:39:51 +0000 jamesingram
I sure you're aware best to use minium height joist possible to maximise hieght saving , perhaps by spanning off mid way supporting wall to plate will reduce span width , rather than sticking in steels like they seem keen to do all the time.
how about I beams , this is interesting
http://www.strongtie.co.uk/iloft/index.php
you could slide in beams from outside , stick them on lower course ,tie them in with rafters , then remove
all unnecessary brickwork /wallplate above this]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135663#Comment_135663 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135663#Comment_135663 Sat, 18 Feb 2012 11:57:10 +0000 Shevek Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135812#Comment_135812 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135812#Comment_135812 Sun, 19 Feb 2012 21:46:51 +0000 jamesingram bit of span spec here for I beams
http://www.trussform.co.uk/download/TJI_Technical_Guide.pdf]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135850#Comment_135850 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=135850#Comment_135850 Mon, 20 Feb 2012 08:18:26 +0000 CWatters Posted By: jamesingramYep like that

As far as i'm aware B.regs require 25mm cont. air gap , most leave 50mm between rafter with old style felt ...

because the felt drapes 25mm mid way between rafters.]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=150777#Comment_150777 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=150777#Comment_150777 Fri, 06 Jul 2012 23:07:34 +0100 Shevek
I'm wondering whether a re-roof is unavoidable. Rip roof and battens up. Add 82.5 mm Kooltherm 18 below rafters, 100 mm K7 full-fill between rafters, breather membrane, new counter-battens (size?), battens, tiles.

This will mean we're higher than the neighbour's roofs. Is this possible?]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=150781#Comment_150781 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=150781#Comment_150781 Sat, 07 Jul 2012 01:06:47 +0100 tony Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161325#Comment_161325 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161325#Comment_161325 Wed, 14 Nov 2012 14:31:53 +0000 Shevek
Any thoughts on avoiding interstitial condensation? Do you think that brickwork upstand will stay warm enough?]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161331#Comment_161331 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161331#Comment_161331 Wed, 14 Nov 2012 16:01:54 +0000 tony Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161571#Comment_161571 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161571#Comment_161571 Sat, 17 Nov 2012 12:04:50 +0000 Shevek Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161644#Comment_161644 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161644#Comment_161644 Sun, 18 Nov 2012 13:53:43 +0000 tony Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161691#Comment_161691 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=161691#Comment_161691 Mon, 19 Nov 2012 08:51:58 +0000 davidfreeborough
If you move the fascia up so that the over fascia vent correctly supports the underside of the tiles then there'll be nothing to fix it to. I would run a continuous tilting fillet or inverted bevelled batten behind the fascia screw fixed to the top side of the rafters.

You probably don't need the short section of soffit board. Just use a fair-faced batten.

David]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180209#Comment_180209 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180209#Comment_180209 Fri, 19 Jul 2013 00:31:51 +0100 Shevek
What do you think? Particularly with regard to the structural studwork being to the outside of the wall (this was London Insulation's suggestion). It's a breathable wall construction.

In fact London Insulation suggested I should do away with the outer skin of OSB as well and just rely on the breather membrane to incase the Icynene. But surely we need that to brace the structure no?

Also what do you think of stopping the flooring way short of studwork like that so as to continue the Icynene through uninterrupted? Probably not good for sound right?]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180217#Comment_180217 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180217#Comment_180217 Fri, 19 Jul 2013 09:19:42 +0100 davidfreeborough
No.18 appears twice. One of them is the Icyene insulation; is the other one OSB flooring? Why three layers of flooring? Couldn't you have fully-floating timber floor boards over a resilient layer over OSB?

OSB or plywood sheating is required in timber framed walls for racking strength. If you've every tried pushing a timber frame out of shape before the sheathing board is fitted then you'll know its needed. I would also have an OSB sarking board to the top of the rafters & counter battens to create a ventilated space above the breather membrane. This is standard practice for timber framed walls, but British builders have got into the habit of leaving it out of timber framed roofs.

I would speak to the breather membrane manufacturer before using it to retain Icyene.

David]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180223#Comment_180223 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180223#Comment_180223 Fri, 19 Jul 2013 10:35:53 +0100 Shevek
No issue with the timber stud edges being expose to the outside then? As long as it's ventilated no problem right?

Posted By: davidfreeboroughWhy three layers of flooring? Couldn't you have fully-floating timber floor boards over a resilient layer over OSB?

Do you mean lay some finishing boards over a separately installed resilient layer? Good thought, much rather do that. Any recommendations for the resilient layer?]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180236#Comment_180236 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180236#Comment_180236 Fri, 19 Jul 2013 13:38:12 +0100 davidfreeborough
http://www.customaudiodesigns.co.uk/isobase.htm

Note that there are a number of resilient layers available for use with screeded floors, but these are not suitable for use with timber floors.

David]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180239#Comment_180239 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180239#Comment_180239 Fri, 19 Jul 2013 13:54:10 +0100 djh Posted By: davidfreeboroughhttp://www.customaudiodesigns.co.uk/isobase.htm

Note that there are a number of resilient layers available for use with screeded floors, but these are not suitable for use with timber floors.

David
From the page you linked:

The product is designed to be used as a resilient layer underneath T&G chipboard type flooring.

This product can also be used on top of a concrete floor.

:confused:]]> Insulation to eaves of existing 42º pitched roof and solid walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180268#Comment_180268 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8593&Focus=180268#Comment_180268 Fri, 19 Jul 2013 16:30:52 +0100 davidfreeborough
David]]>