Jump to content


ebuild is sad to announce its closure - it has become too time and resource intensive to develop, manage and maintain.

However, ebuild will remain on-line in archive mode (ie no posting facilties) for several weeks so that users can use it as an information resource.

Refurbishing A 400 Years Old Chalk Cottage


  • Please log in to reply
13 replies to this topic

#1 frankeg

frankeg

    New Member

  • Members
  • Pip
  • 6 posts

Posted 03 February 2013 - 09:08 PM

Hi, I'm refurbishing a chalk cottage in West Norfolk. The walls are chalk block tapering from 500mm to 400mm with coursed blocks on the face and rubble in the core with lime mortar.
Does anyone know where could I find U values for this type of construction, please?

#2 jsharris

jsharris

    Please ignore all posts by me, some are erroneous

  • Member Blogger
  • PipPipPipPip
  • 11,461 posts
  • LocationWiltshire/Dorset border

Posted 03 February 2013 - 10:28 PM

According to the Engineering Toolbox site, dry chalk apparently has a thermal conductivity of about 0.09 W/m.K, so 500mm thick of dry chalk would give you a U value of around 0.18 W/m².K. A 400mm thick dry chalk wall would give you a U value of around 0.225 W/m².K

Surprisingly good, but I suspect that in a building the chalk won't be 100% dry, so the U values will be a fair bit higher.

#3 frankeg

frankeg

    New Member

  • Members
  • Pip
  • 6 posts

Posted 03 February 2013 - 10:41 PM

View Postjsharris, on 03 February 2013 - 10:28 PM, said:

According to the Engineering Toolbox site, dry chalk apparently has a thermal conductivity of about 0.09 W/m.K, so 500mm thick of dry chalk would give you a U value of around 0.18 W/m².K. A 400mm thick dry chalk wall would give you a U value of around 0.225 W/m².K

Surprisingly good, but I suspect that in a building the chalk won't be 100% dry, so the U values will be a fair bit higher.
Thank for that, I have already made two openings through the wall, at ground and first floor levels and after the first 25mm or so the chalk is amazingly sound and almost as hard as common bricks to drill!

#4 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 04 February 2013 - 08:43 AM

Frank, you sound surprised. :)

It's still a limestone, albeit fine-grained, and becomes lime when heated, so it is inherently a sound construction material with the properties of lime in terms of its capacity to absorb and release surface moisture.

Very attractive too!

Much flint? ;)

#5 frankeg

frankeg

    New Member

  • Members
  • Pip
  • 6 posts

Posted 04 February 2013 - 07:55 PM

View Postjoiner, on 04 February 2013 - 08:43 AM, said:

Frank, you sound surprised. :)

It's still a limestone, albeit fine-grained, and becomes lime when heated, so it is inherently a sound construction material with the properties of lime in terms of its capacity to absorb and release surface moisture.

Very attractive too!

Much flint? ;)
There is flint up to about 300mm above ground level on the external face. The ground floor level is about 500mm below external ground level and there were flooring bricks and pamments laid on "clunch" (a chalk/lime sort of concrete equivalent). I hand dug and barrowed about 60T of muck and there is now a concrete slab with a DPM ready to lay insulation then screed with heating pipes. It keeps me fit and is a lot cheaper than the gym!

#6 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 04 February 2013 - 10:38 PM

Ooooh. Not sure about the dpm and concrete though.

Is there any kind of damp course?

#7 frankeg

frankeg

    New Member

  • Members
  • Pip
  • 6 posts

Posted 05 February 2013 - 03:52 AM

View Postjoiner, on 04 February 2013 - 10:38 PM, said:

Ooooh. Not sure about the dpm and concrete though.

Is there any kind of damp course?
When I bought the cottage there were 2 layers of carpet on opened out fertiliser bags on about 3 to 5 layers of lino on bricks or pamments. In the more trodden areas the bricks (similar to Cambridge Whites) were worn from 3" down to less than 1/2". The only heating was storage radiators and an coal fire. As you might imagine it was damp!. When it is finished, I'm aiming for September this year, the DPM and concrete slab will only be evident by the fact that the floor will be level! Although I am trying to maintain the character of the cottage, there is an amount of compromise to make it habitable and saleable.

#8 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 05 February 2013 - 08:40 AM

:) Frank, understand that regular contributors to forums feel they have an obligation to offer best advice. As any such advice is offered at a considerable distance from the situation known to the OP (Original Poster), we can only ask questions in order to avoid assumptions being made if, because we sense that someone is about to make a mistake, we're about to warn them not to do what they're planning. If they've already done "it" then all we can do is suggest what the possible/probable outcome is likely to be and leave them to cry into their morning coffee.

My expression of "concern" had to do with the dangers of fitting a DPM in a situation that can (and frequently will) divert ground water out towards the walls creating a situation that is extremely difficult to rectify if there is no DPC to limit its travel (penetration) into the walls.

You're in a situation I've seen MANY times, sometimes with horrific results. Without exception they have involved the fitting of a DPM over which a concrete sub floor has been laid.

I would seriously and respectfully suggest that you open a thread on the Period Property Forum because there you will find people who live in similar properties to your own, who have experience of their own renovation and can pass on the results of their research and experience. You'll find them on...

http://www.periodpro...forum/index.php

Good luck. ;)

#9 jsharris

jsharris

    Please ignore all posts by me, some are erroneous

  • Member Blogger
  • PipPipPipPip
  • 11,461 posts
  • LocationWiltshire/Dorset border

Posted 05 February 2013 - 09:31 AM

That's pretty much what happened with my mothers previous farmhouse. That had granite stone walls, rendered and plastered inside, and someone had fitted a concrete slab floor with DPC over what had originally been a rammed earth floor. That had damp running a couple of feet up the walls, driven in large part by the displaced moisture from the relatively new floor (she didn't lay the new floor, the previous owner did).

An injected damp proof course didn't make any difference, and in the end the fix was to strip off all the render and internal plaster and clean up and expose the stone walls. After much cleaning with a needle gun and scrubbing with caustic the stone looked respectable enough to leave. Having open stone inside and out fixed the damp problem, presumably by allowing the moisture to evaporate.

Not a thermally effective scheme by any means, but this was all done back in the late 70's, when we didn't seem too worried about energy.

#10 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 05 February 2013 - 09:48 AM

Yup. She was lucky it was granite.

In a way, anyone buying a Listed building of this type of construction is lucky because they'll be prevented from making such mistake(s) by the involvement of a CO at the outset - always assuming "modernisation" hasn't already been carried out!

#11 frankeg

frankeg

    New Member

  • Members
  • Pip
  • 6 posts

Posted 05 February 2013 - 07:37 PM

View Postjoiner, on 05 February 2013 - 08:40 AM, said:

:) Frank, understand that regular contributors to forums feel they have an obligation to offer best advice. As any such advice is offered at a considerable distance from the situation known to the OP (Original Poster), we can only ask questions in order to avoid assumptions being made if, because we sense that someone is about to make a mistake, we're about to warn them not to do what they're planning. If they've already done "it" then all we can do is suggest what the possible/probable outcome is likely to be and leave them to cry into their morning coffee.

My expression of "concern" had to do with the dangers of fitting a DPM in a situation that can (and frequently will) divert ground water out towards the walls creating a situation that is extremely difficult to rectify if there is no DPC to limit its travel (penetration) into the walls.

You're in a situation I've seen MANY times, sometimes with horrific results. Without exception they have involved the fitting of a DPM over which a concrete sub floor has been laid.

I would seriously and respectfully suggest that you open a thread on the Period Property Forum because there you will find people who live in similar properties to your own, who have experience of their own renovation and can pass on the results of their research and experience. You'll find them on...

http://www.periodpro...forum/index.php

Good luck. ;)

Thanks and I do appreciate your advice and will follow the link you suggest. I really only started the thread because I wasn't confident of the U value of the walls and haven't really described the whole picture. I have already taken account of the problem in the walls and have previously taken advice from the district Building Control Inspector and a neighbour who specialises in refurbishment in my area. I'm reasonably confident that their suggestions will work. He won't issue a final completion certificate unless he is content with what I have done. Hopefully I'll post again in a few months to report whether their advice was good!!! (That's assuming we have another wet "summer" to put it to the test!)

Edited by joiner, 05 February 2013 - 11:08 PM.
Repeated quote erased


#12 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 05 February 2013 - 11:09 PM

:) ;)

#13 frankeg

frankeg

    New Member

  • Members
  • Pip
  • 6 posts

Posted 16 February 2013 - 04:51 PM

View Postfrankeg, on 05 February 2013 - 07:37 PM, said:

Thanks and I do appreciate your advice and will follow the link you suggest. I really only started the thread because I wasn't confident of the U value of the walls and haven't really described the whole picture. I have already taken account of the problem in the walls and have previously taken advice from the district Building Control Inspector and a neighbour who specialises in refurbishment in my area. I'm reasonably confident that their suggestions will work. He won't issue a final completion certificate unless he is content with what I have done. Hopefully I'll post again in a few months to report whether their advice was good!!! (That's assuming we have another wet "summer" to put it to the test!)
(Pls excuse double entry on last post). I've found BRE Digest 245 and a plain English explanation of what, and more particularly, what it doesn't say on the "Ask Jeff" website to be useful regarding this topic. Perhaps I should also say that I graduated from the City University in 1974 with an BSc(hons) in Civil Engineering and my work included a lot of D&B in the building industry.

#14 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 16 February 2013 - 06:25 PM

Fair do's.

Any of us can only speak from experience. :)