From Newsgroup: uk.d-i-y

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.
--
Cheers,

John.

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From Newsgroup: uk.d-i-y

On 30/06/2026 16:27, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

Wow! What a cracking job John. Glad I didn't have to do that - it would probably have killed me.
Thank you.
--
Regards
wasbit
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From Newsgroup: uk.d-i-y

On 01/07/2026 09:28, wasbit wrote:

On 30/06/2026 16:27, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?
title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

Wow! What a cracking job John. Glad I didn't have to do that - it would probably have killed me.
Thank you.

Yeah, well it seemed simple enough in concept... but turned out to be
quite a endurance marathon in the end!
--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/
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From Newsgroup: uk.d-i-y

On 30 Jun 2026 at 16:27:12 BST, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

Looks superb, well done. I'll have a proper read later. Initial Qs:

* How much did it/would it cost - say, overall and per m2? -u30k overall, if labour is -u400/day? A.I. reckons -u100 - -u200 m2. Scaffolding is a big chunk of
the cost - maybe -u1000/week for wrap-around scaffold in your case? Almost worth buying?!

* I can't see (from a quick read) how the ground level/below DPC detailing was achieved. Did you go below ground/switch to XPS for example? Or accept a bit
of compromise insulation wise at ground level?

* I'm having a bit of an ongoing argument/discussion with a planner friend about planning permission/regs compliance - he seems to think that such work
is not within permitted development. I think it is - obviously assuming no conservation and listed type considerations. Also building regs - did that significantly inform your design decisions? I'd assume you self-certify? TBH I'm still confused about the whole regs and retrofit compliance side of
things, how regs 'equal' PAS 2030 etc. . . . (!)
--
Cheers, Rob
Sheffield, UK
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From Newsgroup: uk.d-i-y

On 01/07/2026 10:49, RJH wrote:

On 30 Jun 2026 at 16:27:12 BST, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

Looks superb, well done. I'll have a proper read later. Initial Qs:

* How much did it/would it cost - say, overall and per m2? -u30k overall, if labour is -u400/day? A.I. reckons -u100 - -u200 m2.

I have no idea what a commercial quote would be.

The insulation was -u1,250, and the main cladding order with most of the
trims etc was about -u6,700. When you add in all the other stuff like
screws, sand cement, linear drain, timber battens, and a shed load of
tapes, sealants, glues etc and a skip or two then you are up to about -u10,300.

(I also bought some extra tools - but since I get to keep them, I don't include them in the cost unless they are "consumables" (blades, discs etc))

Scaffolding is a big chunk of
the cost - maybe -u1000/week for wrap-around scaffold in your case? Almost worth buying?!

The scaffolding cost -u936 and I kept it for about 4 weeks. So perhaps
half as much again if also doing the back. I bought some ordinary
building trestles for the easy side - those were about -u145 inc
delivery. An extra 4 might have been worth it - but the layout of the
planks enforced by the windows made it easy enough to do in sections
without needing to move the access kit too much.

* I can't see (from a quick read) how the ground level/below DPC detailing was
achieved. Did you go below ground/switch to XPS for example? Or accept a bit of compromise insulation wise at ground level?

Thus far I have not changed anything below interior floor level. The underfloor volume is vented (air bricks etc) so I is questionable if
there is much additional value to insulating the "skirts" at the side.

* I'm having a bit of an ongoing argument/discussion with a planner friend about planning permission/regs compliance - he seems to think that such work is not within permitted development. I think it is - obviously assuming no conservation and listed type considerations.

I did a bit of research on whether changes to the visual appearance were
of consequence. From what I could find, the answer was no, unless in a conservation area. (also the change in appearance is in keeping with the
local architectural style, and does not affect the road facing elevation anyway)

Also building regs - did that
significantly inform your design decisions? I'd assume you self-certify? TBH I'm still confused about the whole regs and retrofit compliance side of things, how regs 'equal' PAS 2030 etc. . . . (!)

I don't have an answer for the more general question...
--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/
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From Newsgroup: uk.d-i-y

On 01/07/2026 10:00, John Rumm wrote:

On 01/07/2026 09:28, wasbit wrote:

On 30/06/2026 16:27, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?
title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

Wow! What a cracking job John. Glad I didn't have to do that - it
would probably have killed me.
Thank you.

Yeah, well it seemed simple enough in concept... but turned out to be
quite a endurance marathon in the end!

I have clad farm buildings with feather edge treated timber over rigid
foam using *lost tite* screws. Basically a woodscrew with a long plain
shank but having retaining rings near the head.

Mostly screwed into timber building frame but also works for brick/block.

With the insulation and first board temporarily located, drill through
from the outside using a suitable masonry or conventional drill. Start a fixing plug to the screw and tap into the hole. Use drill driver to seat
home and move on to the next fixing. Once the board ends are secure, the
whole row of new fixings can be drilled to save swapping drill bits.

I have no idea where this might fit in building regulations:-)>

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From Newsgroup: uk.d-i-y

On 01/07/2026 15:24, Timatmarford wrote:

I have clad farm buildings with feather edge treated timber over rigid
foam using *lost tite* screws. Basically a woodscrew with a long plain
shank but having retaining rings near the head.

Mostly screwed into timber building frame but also works for brick/block.

An interesting method. Something of a possible fire risk for a two
storey building

With the insulation and first board temporarily located, drill through
from the outside using a suitable masonry or conventional drill. Start a fixing plug to the screw and tap into the hole. Use drill driver to seat home and move on to the next fixing. Once the board ends are secure, the whole row of new fixings can be drilled to save swapping drill bits.

I have no idea where this might fit in building regulations:-)>

Well planning might have someth9ing to say as it changes the overall appearance.
But I think from an engineering perspective, insulation *inside* an e,g. single brick wall is about as good as it gets for preserving thermal
mass inside the barrier

I haven't thought the implications for damp through. of course.
--
rCLPuritanism: The haunting fear that someone, somewhere, may be happy.rCY

H.L. Mencken, A Mencken Chrestomathy

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From Newsgroup: uk.d-i-y

On 01/07/2026 15:24, Timatmarford wrote:

On 01/07/2026 10:00, John Rumm wrote:

On 01/07/2026 09:28, wasbit wrote:

On 30/06/2026 16:27, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?
title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

Wow! What a cracking job John. Glad I didn't have to do that - it
would probably have killed me.
Thank you.

Yeah, well it seemed simple enough in concept... but turned out to be
quite a endurance marathon in the end!

I have clad farm buildings with feather edge treated timber over rigid
foam using *lost tite* screws. Basically a woodscrew with a long plain
shank but having retaining rings near the head.

Mostly screwed into timber building frame but also works for brick/block.

With the insulation and first board temporarily located, drill through
from the outside using a suitable masonry or conventional drill. Start a fixing plug to the screw and tap into the hole. Use drill driver to seat home and move on to the next fixing. Once the board ends are secure, the whole row of new fixings can be drilled to save swapping drill bits.

Pretty close to the process I was using. I placed the gecko gauges about
70mm in from each edge - that kept the board supported without any
visible sag. Then whizzed in a couple of screws to hold it, then filled
in the gaps. I normally did the end ones last since I liked to give the
board a little tickle with the drill. It also leaves hands free to mess
with getting the EDPM strip under the butt join. Using the small combi
drill that fits into the pouch on my tool belt, and the 18V ID that I
can hang from a loop - so no swapping bits, just tools!
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/
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From Newsgroup: uk.d-i-y

On 30/06/2026 16:27, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php? title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

My neighbours clad their house. They used masses of rock wool, which is inherently non-combustible. Did you consider that, instead of PIR?

I appreciate that PIR, applied in the way you have, with a cement board cladding is not really a fire risk, and it's a low rise building, but ...




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From Newsgroup: uk.d-i-y

On 02/07/2026 12:12, GB wrote:

On 30/06/2026 16:27, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?
title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

My neighbours clad their house. They used masses of rock wool, which is inherently non-combustible. Did you consider that, instead of PIR?

Not really... rockwool would have needed significant extra thickness to achieve similar performance. So with the space available that could
knock the u value up from ~0.3 to something like ~0.45.

To be fair, even 0.45 would still be a dramatic performance improvement
over the typical 2.1 ish of a rendered solid brick wall, but that is
still quite an extension in payback time (although that was not the
primary driver).

You would need to use something like Rockwool Rainscreen Duo Slabs,
which are significantly more pricey than what you would pay for PIR
boards - so that would add to the build cost.

I appreciate that PIR, applied in the way you have, with a cement board cladding is not really a fire risk, and it's a low rise building, but ...

Yup fire risk was definitely a consideration. One of my reasons for
rejecting a traditional timber cladding (that and maintenance).

PIR generally ought not sustain a fire - but much depends on how much
extra flammable stuff there is around it, and how much chimney effect
you get. Hopefully there is not too much scope for ignition in the first place!
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 1 Jul 2026 at 12:39:06 BST, John Rumm wrote:

On 01/07/2026 10:49, RJH wrote:

On 30 Jun 2026 at 16:27:12 BST, John Rumm wrote:

I wrote some stuff about my recent experiences...

https://wiki.diyfaq.org.uk/index.php?title=External_wall_insulation,_a_case_study

Probably still needs a bit of tweaking, so let me know if you spot
anything that does not make sense, or is missing.

Looks superb, well done. I'll have a proper read later. Initial Qs:

* How much did it/would it cost - say, overall and per m2? -u30k overall, if >> labour is -u400/day? A.I. reckons -u100 - -u200 m2.

I have no idea what a commercial quote would be.

-u400 per person/day, at a guess.

The insulation was -u1,250, and the main cladding order with most of the trims etc was about -u6,700. When you add in all the other stuff like
screws, sand cement, linear drain, timber battens, and a shed load of
tapes, sealants, glues etc and a skip or two then you are up to about -u10,300.

Interesting, thanks.

(I also bought some extra tools - but since I get to keep them, I don't include them in the cost unless they are "consumables" (blades, discs etc))

Scaffolding is a big chunk of
the cost - maybe -u1000/week for wrap-around scaffold in your case? Almost >> worth buying?!

The scaffolding cost -u936 and I kept it for about 4 weeks. So perhaps
half as much again if also doing the back. I bought some ordinary
building trestles for the easy side - those were about -u145 inc
delivery. An extra 4 might have been worth it - but the layout of the
planks enforced by the windows made it easy enough to do in sections
without needing to move the access kit too much.

Trestles would safely see to over half the height, saving a fair chunk of the scaffold hire. If storing the trestles (or selling them) isn't a problem, a good investment.

* I can't see (from a quick read) how the ground level/below DPC detailing was
achieved. Did you go below ground/switch to XPS for example? Or accept a bit >> of compromise insulation wise at ground level?

Thus far I have not changed anything below interior floor level. The underfloor volume is vented (air bricks etc) so I is questionable if
there is much additional value to insulating the "skirts" at the side.

Gotcha.

* I'm having a bit of an ongoing argument/discussion with a planner friend >> about planning permission/regs compliance - he seems to think that such work >> is not within permitted development. I think it is - obviously assuming no >> conservation and listed type considerations.

I did a bit of research on whether changes to the visual appearance were
of consequence. From what I could find, the answer was no, unless in a conservation area. (also the change in appearance is in keeping with the local architectural style, and does not affect the road facing elevation anyway)

Also building regs - did that
significantly inform your design decisions? I'd assume you self-certify? TBH >> I'm still confused about the whole regs and retrofit compliance side of
things, how regs 'equal' PAS 2030 etc. . . . (!)

I don't have an answer for the more general question...

It was more how PAS/regs/certification etc informed your project. Looks
'right' to me . . .
--
Cheers, Rob
Sheffield, UK
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From Newsgroup: uk.d-i-y

On 02/07/2026 15:00, RJH wrote:

On 1 Jul 2026 at 12:39:06 BST, John Rumm wrote:

On 01/07/2026 10:49, RJH wrote:

* How much did it/would it cost - say, overall and per m2? -u30k overall, if
labour is -u400/day? A.I. reckons -u100 - -u200 m2.

I have no idea what a commercial quote would be.

-u400 per person/day, at a guess.

Yup quite possibly... I could see that would soon double (or more) the price...

The insulation was -u1,250, and the main cladding order with most of the
trims etc was about -u6,700. When you add in all the other stuff like
screws, sand cement, linear drain, timber battens, and a shed load of
tapes, sealants, glues etc and a skip or two then you are up to about
-u10,300.

Interesting, thanks.

Scaffolding is a big chunk of
the cost - maybe -u1000/week for wrap-around scaffold in your case? Almost >>> worth buying?!

The scaffolding cost -u936 and I kept it for about 4 weeks. So perhaps
half as much again if also doing the back. I bought some ordinary
building trestles for the easy side - those were about -u145 inc
delivery. An extra 4 might have been worth it - but the layout of the
planks enforced by the windows made it easy enough to do in sections
without needing to move the access kit too much.

Trestles would safely see to over half the height, saving a fair chunk of the scaffold hire. If storing the trestles (or selling them) isn't a problem, a good investment.

They go up to about 1.6m IIRC (although are a bit wobbly - so benefit
from some bracing!) - the top of the wall was about 3.4m above the
actual ground level at the side (the place has downstairs ceilings over
10', so it is taller than it looks). However I am quite long, so
comfortably within reach :-)

I did a bit of research on whether changes to the visual appearance were
of consequence. From what I could find, the answer was no, unless in a
conservation area. (also the change in appearance is in keeping with the
local architectural style, and does not affect the road facing elevation
anyway)

Also building regs - did that
significantly inform your design decisions? I'd assume you self-certify? TBH
I'm still confused about the whole regs and retrofit compliance side of
things, how regs 'equal' PAS 2030 etc. . . . (!)

I don't have an answer for the more general question...

It was more how PAS/regs/certification etc informed your project. Looks 'right' to me . . .

Approved doc L1[1] has a bit to say on target performance for renovated
or upgraded thermal elements of a building. The "improved" target they
quote in table 4.3 (col B) is a U value of 0.3, and the lower threshold specified (col A) is 0.7.

However there are several mitigations:

"If achieving the U-value in Table 4.3, column (b) either:
a. is not technically or functionally feasible or
b. would not achieve a simple payback of 15 years or less
then the element should be upgraded to the lowest U-value that both:
a. is technically and functionally feasible and
b. can achieve a simple payback not exceeding 15 years

Generally, a thermal element once upgraded should not have a U-value
greater than 0.7W/(m2-+K). A lesser standard for the thermal element may
be acceptable where work complies with Part C of the Building
Regulations on protection from the harmful effects of interstitial and
surface condensation."

[1] https://assets.publishing.service.gov.uk/media/662a2e3e55e1582b6ca7e592/Approved_Document_L__Conservation_of_fuel_and_power__Volume_1_Dwellings__2021_edition_incorporating_2023_amendments.pdf

Basically I was going for the best I could manage within the constrained depth... I would estimate that the result is actually pretty close to
the "improved" target, and comfortably within the 0.7 fallback.

(however there are lots of other bits that could also do with
improvement, like insulating under the suspended timber floor - I but I
will save that for another day!)
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/
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