Single skin, tile clad dormers - how to refurbish

[StuGregory]

Hi folks,

I am looking for advice on my issue which is:
I am building my own extension (no problems there) however my property is basically single story with dormer windows spanning the front and rear elevation that are tile hung. In the plans i have submitted the specification was to change the tile hung for vertical T&G cladding.
On inspection of one of the existing dormer cheeks, i have found that the construction of the dormer is an internal single skin, some tar paper, batons and then tiles. The blocks for the internal skin are of the old cinder variety and have many holes. Which answers me why upstairs is always colder than downstairs.
After speaking with planning and asking if i could do insulated render instead, i have been informed that they would like me to keep the dormers "in keeping" with the tiles on the roof.
So here is where I need advice.......
What to do in terms of insulation? thickness and product (as space is limited to the size of the flat roof decking on the dormer approx 90mm from block wall to backside of fascia board)
Any ideas on long lasting cladding?

Thanks for your time, i've been banging my head on a brick wall for days!

Regards, Stu

 

[Blagard]

Have you been able to check for insulation in the dormer flat roof? That is where you would loose a lot of heat and it is easily missed in construction.
I have removed plasterboard soffits on dormers to find them totally devoid of any insulation.

As for the cheeks, I think that is extremely difficult to improve upon. I would guess the internal side does not leave much scope for lining with an insulated plasterboard ?

 

[^woody^]

You can construct a timber frame dormer with 100mm timber and 100mm celotex between the timber and then faced with your cladding, and this will meet b/regs

For the cladding, you can tile or slate hang, or get a cement board product that will look like or match tiles in colour

As for the planners "in keeping" statement, is that a condition or just a request? I doubt if they can actual insist on no render.

Also, "in keeping" does not mean "the same as" and rendered dormers are more common than tile hung ones

 

[Blagard]

You can construct a timber frame dormer with 100mm timber and 100mm celotex between the timber and then faced with your cladding, and this will meet b/regs

But surely this means demolishing the existing blockwork? or are you thinking this can be planted on ? If replacement build, will it also support the same loads the blockwork currently takes, bearing in mind the the dormer spans are currently an unknown quantity.

 

[^woody^]

I'm confused ... I thought he OP said that he was building his extension?

If the dormers are already there then its got nothing to do with planning if they are rendered or not - in which case he can do it all from outside and then render or re-clad

 

[Blagard]

StuGregory.

I was under the impression from your post that your concern was with the existing dormers.
1 You want to improve the insulation to the cheeks.
2 You wanted to change the cladding to them (for improved insulation) but are limited by the space available under the dormer roof. And planning don't want you to change the appearance of them (for whatever reason)

Is your property in an area where the appearance cannot be changed without planning approval ? Such as a conservation area etc.

After rereading your post It also seems you may just be asking if you can build new dormers on your extension different to the original, which of course you can, almost irrespective of the cladding used.

Can you clarify - I'm probably just a bit thick.

 

[StuGregory]

Firstly thanks for all you responses.
The planning department require me to submit "full" planning request to change the original plan from vertical board cladding to insulated render.
The "in keeping" statement was made by planning after the advice on havingh to submit full plans. i cant fully remember the sentance but it was along the lines of: similar colour, material blah blah as the roof that surrounds the dormers.
I shall post some pictures asap to help.
My question is about the existing dormers. Building control have advised that as the change of cladding is in the plans that they should be upgraded to current insulation regs. My problem is that the rooms are not big enough inside to insulate and i am not sure I can achieve building regs on the outside due to the distance between the outside of the block wall and the backside of the fascia.
I hope that this clarifies a few questions.
thanks again, its nice that people are here to help.

 

[StuGregory]

i have uploaded a picture nut cant seem to get it on the thread.
sorry

 

[freddiemercurystwin]

Untitled

• StuGregory
• 4 Sep 2011
• 1

 

[Blagard]

Nice bit of support there from freddymercurystwin , but where's your solution to this one

I have to say that looking at the photo I can not offer a constuctive suggestion of how to deal with upgrading the thermal insulation of the existing dormer externally. There is so little space to play with.

I have this feeling again (woody ,private joke) that the answer lies with going back to planning and matching the appearance of the new dormers to the existing ones. At least you can get the thermal values up to spec on the new build. I appreciate this is not what you set out to do, but short of losing space inside the existing dormers, I can't see a remedy, other than a rebuild of the existing dormer cheek and possibly even the area around the dormer windows.

I hope some-one here can.

 

[^woody^]

Sorry but I am still confused .. mainly regarding planning and b/regs comments. You seem to be bringing a lot of this headache on yourself, or there is a communication mix up, as it all seems unnecessary

"The planning department require me to submit "full" planning request to change the original plan from vertical board cladding to insulated render."

Why? This is a minor change, and can be done without applying or as a rider. Have you questioned this, or has your agent given you some advice? Basically you send a note saying "I want to clad the dormer in x"

Presumably your comments just relate to the new extension plans as planning should not be involved with the existing dormer?

"The "in keeping" statement was made by planning after the advice on havingh to submit full plans."

As I said previously 'in keeping' does not mean 'the same as'

"My question is about the existing dormers. Building control have advised that as the change of cladding is in the plans that they should be upgraded to current insulation regs."

Why has the change of cladding been included in your extension plans? There was no need, and I can't see why they are involved with it

Also, if this is because of the 25% renovation rule, then that only requires you to make "reasonable attempts" at increasing insulation, and it must be financially viable

So if the BCO wants you to add insulation and you then have to mess about with other parts of the structure so that you end up paying £1k to save £10 a year, then you don't have to insulate. Your agent should have advised you about this

"My problem is that the rooms are not big enough inside to insulate and i am not sure I can achieve building regs on the outside due to the distance between the outside of the block wall and the backside of the fascia."

If you are taking off the tiles to re-clad, then its just a case of removing tiles, fitting the insulation (80mm celotex) and then cladding. You will have an issue below the fascia in which case you either use a lead apron to cover the projecting cladding (may look a bit crap), or you extend the fascia out by planting on a new timber and fascia

IMO, you need to clarify why planning and b/regs have asked you to do those things as it seems that they are asking for them without good reason

 

[StuGregory]

Thanks again for everyone's input.

I have now got to a point where i need advice on certain products to insulate my existing dormers.
I will be using a shiplap cedar cladding vertically.
I have spoken to two companies both not endorsing each others products.
Superfoil for their SFUF Insulation (constructed of 25mm baton, SFUF, 25mm baton, breathable membrane and then cladding)
OR
Web Dynamics TLX Gold with 38mm batons instead.

Anyone got any ideas.

 

[mointainwalker]

I still have significant doubts about multi-foils so personally would not want to use them but see how they may solve your regs. problem

The Web Dynamics site does at least list who tested their materials and shows the certificates whilst the SF site talks about "internationally approved independent laboratories" but never names them and simply shows a letter from Ealing Council as their bona fides. Rather thin methinks.