Extending period properties

[overlander matt]

I'm keen to get some thoughts on extending our period property, in terms of design and construction methods. Our house has a Georgian 'core' with two Victorian add-ons and two further Edwardian alterations. So while the front of the house looks classic Georgian, round the back is a bit of a mix and there have been a few less desirable alterations too in the form of a patio door and casement windows. However, should these alterations not have been made then getting permission to extend the building would most likely have been more difficult.

Our local CO, before she departed unexpectedly, was very helpful in suggesting the most obvious place for an extension and to date the council planners have more or less agreed to the following single storey extension:





I've been very critical of poorly considered extensions in the past and don't want to get it wrong on this house. I think I would prefer a style that is in keeping with the original building rather than going for a total contrast. The main aim was to reconfigure the downstairs living areas to overlook the garden with the extension being designed loosely in the style of a Victorian orangery. Over the next few weeks we can tinker with some design elements and start to consider the right materials and construction methods. Council feedback on the design suggested more glass was needed...

In terms of construction techniques, how does one integrate modern building methods with the traditional and what care the most common challenges? Everything I have been doing in the old part of the house is focussed on making the house breathable and now I will end up doing the complete opposite with this extension. While both traditional and modern work in their own right, how do they perform where the old and new meet?

Any ideas would be much appreciated.

Thank you.

Matt

 

[a twig]

There's a lot from SPAB on this:

Here's a good start:
https://www.spab.org.uk/advice/alterations-and-extensions-listed-buildings

New Design for Old Buildings – Roger Hunt and Iain Boyd, with Foreword by Kevin McCloud (2017)
SPAB / RIBA Publishing, ISBN 978-1-85946-612-4 (The book contains a helpful bibliography.)

The SPAB Approach: the conservation & care of old buildings – Matthew Slocombe (2017) available on
the SPAB website: https://www.spab.org.uk/campaigning/spab-approach

Building on the Past – Roger Hunt and Iain Boyd in SPAB Magazine, Autumn 2017, pp36-41

 

[plasticpigeon]

My thoughts are probably not what you want to hear. My initial thought is, you have a massive house, do you really need to extend, can you not embrace it as is?

I'm afraid I'm not very keen on the extension plans. I've seen extensions like that and I think they look ungainly personally. Flat roofs with lanterns look very modern to me. I don't like the soldier courses at all. They would look nicer as arches if the structure has to be brick! Is that 3 sets of bifold doors?

If you'd like a Victorian orangery, I'm sure there is scope to pursue something a bit closer to a traditional design. Brick base, much more glass with fancy windows, pitched roof, with lantern if you like, or if it has to be in that position a lean to conservatory?

 

[88v8]

...I would prefer a style that is in keeping with the original building rather than going for a total contrast

Entirely agree with you.
The 'of its time' approach is to me a total cop-out.

However, while its hard to tell from a small rendering, the addition looks rather 60s. The soldiers are indeed an "oh dear" feature. And those great slabs of glass, presumably sealed units and unless they are hand-made glass (££) they will look like sealed units with that sort of ghastly concave effect.

Fortunately nowadays there are many options in terms of conservatories or orangeries that would do the house more justice. Elegant, and of a 'period' look.
Randomly, here for example https://www.orangeries-uk.co.uk/choosing-a-period-conservatory.html
One reason that planners like more glass is that one can 'see' the original house, and the extension does not impose itself so much.

And I'm sure that if you ever sell, you will find that buyers much prefer a classic conservatory.

Just my thoughts.

In terms of construction techniques, how does one integrate modern building methods with the traditional and what care the most common challenges? Everything I have been doing in the old part of the house is focussed on making the house breathable and now I will end up doing the complete opposite with this extension. While both traditional and modern work in their own right, how do they perform where the old and new meet? '

Very good question.
Don't recall, does the house have an effective dpc? If so, the walls are not really breathing as they won't be damp, so what you put up against them is of less importance.
If you want to guarantee the minimum impact, you could go for a limecrete floor and of course no dpm. But then the conservatory would need a small degree of permanent ventilation.

Downstairs, you have a suspended floor iirc
If the new floor height means that the vents will be submerged, ensure there is good ventilation under the extension by inserting 4" plastic piping under the new floor to connect from new external air vents to the existing vents. Preferably knock through a few additional vents before you start.

It's nice to have somewhere to sit and look out at the garden on wet days.
Final thought; if it's south facing, roof vents will do more to keep it cool than any amount of expensive blinds. Even better if it also has vents low down, like gunports, so cool air can enter.
In the conservatory on our previous house we had greenhouse openers controlling the roof hatches. A nice low tech solution.

Ivor

 

[overlander matt]

Thanks for your replies. I expected that extending a period property would not be everybody's cup of tea!

Why extend PP? The house had a lot of bedrooms (7 and no bathroom!) dating from a time when it required a staff to run it but unfortunately it has limited space on the ground floor where most people tend to live these days. Only the kitchen currently overlooks the garden via a plastic patio door. Ultimately, the layout doesn't work terribly well.

Getting the design 'right' is important and we will hone our initial design until it works better than the initial sketches. Despite the 'Victorian orangery' style mentioned in my last post, we're not trying to build a conservatory. The room needs to be more versatile than that for year round living. This corner of the house has previously accommodated a lean to structure and to be honest is fairly ugly in terms of the 1980s windows, doors and brickwork repairs. There is nothing of interest to show off or maintain and the right design will, I hope, improve this aspect of the property.

I'm a bit surprised about the dislike for a soldier course. Is that really such a major faux pas? That's good to know and certainly not a must-have in my book! We will probably look to add a corbel detail to the brickwork that exists elsewhere on the property. Sure we will most likely need to do a flat roof on the extension to maintain a high ceiling and not impair the view of the feature arched window. With a parapet wall and natural stone coping to match another section of wall in the garden, I think this can work well. On the glazing front, I can confirm that 3 bifold doors have been included but the style has yet to be decided - glazing bars or no glazing bars...

Marrying the old with the new in terms of construction methods was the main motivation for the original post. Thanks for your thoughts on this Ivor. To date, I have not seen any evidence of problems stemming from breathability issues in the areas close to the extension even with bitumen sealed floors and cement mortar/gypsum plaster. We don't have a dpc in the property. This hopefully indicates there won't be problems created by the extension. Although we have some suspended timber floors, those closest to the extension are solid so no need to worry about ventilation matters. The architect has submitted our application with a concrete floor rather than limecrete but I'm not fussy either way.

Anyway, that's enough typing for one evening. Midway through a 6 week scaffold hire and more planning needed to keep the work on track...

Thanks again.

Matt

 

[Flyfisher]

Thanks for your replies. I expected that extending a period property would not be everybody's cup of tea!

I had a similar experience when discussing our extension some years ago. Only to be expected really but we’re very happy with the result and so, presumably, is our CO (who actually suggested the extension!) and English Heritage (at the time, now Natural England) who was also involved as we are G2*. So as well as having C17 and C18 additions, the house now has a C21 addition - the only one to have had ‘professional’ consent :wink:

Why extend PP? The house had a lot of bedrooms (7 and no bathroom!) dating from a time when it required a staff to run it but unfortunately it has limited space on the ground floor where most people tend to live these days. Only the kitchen currently overlooks the garden via a plastic patio door. Ultimately, the layout doesn't work terribly well.

We extended for pretty much the same reason - i.e. practicality, not for more space. If we could afford staff then the layout would have been fine but, like it or not, that’s not how most households are run these days and (as English Heritage readily acknowledged to me) if listed period properties are not allowed to be changed to accommodate the way people live today then they will become unappealing, unmarketable, then empty, then derelict, then gone. Our addition meant that we did not have to change the use or layout of the existing rooms (by conversion into a kitchen) plus, of course, additions have a minimal effect on the existing fabric so that should any future buyer really take umbrage they could, in theory, demolish the addition and restore the house to its ‘former glory’. Assuming they could get LBC. :wink:

 

[a twig]

Well I like it, it is your house and if the addition gives you what you need to keep living there and enjoying and looking after the property then good for you!

 

[88v8]

I'm a bit surprised about the dislike for a soldier course. Is that really such a major faux pas?

Yes, imho. A modern 'can't be bothered' methodology unworthy of your efforts.

To date, I have not seen any evidence of problems stemming from breathability issues in the areas close to the extension even with bitumen sealed floors and cement mortar/gypsum plaster. We don't have a dpc in the property.

No dpc? Hmmm. Then I would definitely limecrete the new floor.
If there is no damp in the walls, you are lucky. I sometimes think this should be named The Damp and Other Things forum.

With a concrete/dpm floor, whatever damp there may be underneath will go sideways and some of it will end up in the house wall. It may take years for this to become apparent, but then you'll be in a pickle.
This happened to our cottage in 1993. A lean-to was rebuilt, with concrete/dpm and the adjacent original 18" stone wall is now damp for two feet up, but only on the lean-to side. The only damp wall in the house. Dunno how long it took for the damp to manifest. Nothing I can do about it, apart from digging up the floor which isn't going to happen. Fortunately, in the lean-to the damp wall doesn't matter, but that's pure luck.

We also had a concrete/dpm floor in the adjacent sitting room, that floor dated back to the 70s. The perimeter was so damp the Gripperods had rotted. That was dug up and limecreted in 2012, now no damp

Your architect went for concrete as a default, I guess. The extra cost of limecrete would not be significant relative to the overall cost, but you will have future-proofed yourself and the house.
With limecrete, you will never do any harm. Do no harm, a good motto for the custodianship of a period house.

Ivor

 

[Flyfisher]

As far as I can understand, plonking a new concrete floor slab inside an existing room where the house has no DPC is rather different to a new addition built to modern regs.

Our new kitchen extension was built to modern regs, ie concrete foundations, brick and block, insulated, etc etc. However, when it came to the floor slab we left a 600mm gap between the house and the new slab and filled it with limecrete, on the assumption that any damp that was channelled towards the house by the new extension floor could dissipate through the band of limecrete floor before troubling the original walls.

I was a bit wary of this because we also installed under floor heating in the new kitchen and I was a little worried about differential movement between the concrete and limecrete exacerbated by the UFH temperature cycles. Nevertheless, that’s what we did and subsequently laid new clay pamments (bedded in lime mortar) across the whole floor while I crossed my fingers that there would be no problems with the pamments cracking along the junction between the concrete and limecrete floor slabs. Nearly seven years on there is no sign of the pamments cracking and no apparent dampness in the original house walls. Perhaps seven years is too soon for definitive proof but so far, so good.

Perhaps one other thing may be helping. The floors in the original rooms adjacent to the new extension are suspended (loose bricks and tiles on earth supporting the joists) but the only two airbricks were not only blocked but were on the opposite side of the house to the extension. Even so, damp was not a particularly evident problem. However, while building the extension, holes were made in the adjoining wall and plastic down pipes were inserted into the holes before the new floor was poured and through the new extension outer wall to new airbricks, thus allowing good airflow under the original suspended floors, from the front and rear of the house.

Anyway, read into all this whatever you wish, but it all seems to be working so far.

 

[88v8]

It seems a botheration to lay both concrete and limecrete, but I'm sure there was a rationale.

We did something in the same idiom in ths sitting room; the limecrete was overlaid with stone slabs, and in order to get more breathability around the perimeter we laid a 12/18" border of quarries. The floor, as we know, ultimately breathes through its pointing, and there is more pointing in 6" quarries than in large slabs.

I think the takeaway is that something should be done, as distinct from nothing which is what a concrete floor amounts to.

Ivor

 

[MatthewC]

I'm a bit surprised about the dislike for a soldier course. Is that really such a major faux pas?

Yes, imho. A modern 'can't be bothered' methodology unworthy of your efforts.

I'm quite surprised by that view as soldier courses are not new, surely?

My house was converted from a rectangular school building (in rectangular limestone block) to a pair of semis in about 1860 (I believe) by adding rooms at the back of the old building. This "new work" was done in random rubble limestone, with gentle arches above all the windows - the arch is gentle as the centre is barely one inch higher than the ends. These arches are essentially a soldier course of red bricks which I understand were called "rubbers" because they had been rubbed to give a very slight taper and hence the necessary support to the arch. See photos on my blog at https://houseintheenchantedforest.blogspot.com/2013/08/window-arch-repair.html

To all intents and purposes this is a soldier course and, I suspect, is the origin of the "modern" soldier course (which of course is supported usually by a metal lintel behind the brick). I don't know precisely when such a technique was started, but it is surely not out of place on a Georgian/Victorian/Edwardian building?

Matthew

 

[Abi Cott]

My last house had "rubbers" and a soldier course for the window sill built c.1843

 

[plasticpigeon]

Do you have a picture Abbi? The soldiers spanning a huge opening would never have been self supporting and look awful to me. I'm surprised by people saying there is precedent as I have never seen them. The arch in Matthews house is very narrow and it doesn't extend past the end of the window, and it failed. It is still arched though and it does look nice now matthew has repaired it. Of course people can do what they like, but Matt asked a question, and I do believe long rows of soldiers don't look good. If it was my house, I would take a very different approach anyway.

 

[Abi Cott]

Mine was also a small span, only the width of a single sash.

This is the best photo I can find (knicked from Google maps).

The bathroom window on the left is an addition. Yes, yes, we were young and inexperienced, at least we tried!! Lol.

The bedroom window to the right is original and the pattern was copied on the ground floor out of sight.

 

[Abi Cott]

Ok link doesn't look like it's working in the text. Try this
https://imgur.com/a/sWwtyxV

 

[Flyfisher]

It seems a botheration to lay both concrete and limecrete, but I'm sure there was a rationale.

We did something in the same idiom in ths sitting room; the limecrete was overlaid with stone slabs, and in order to get more breathability around the perimeter we laid a 12/18" border of quarries. The floor, as we know, ultimately breathes through its pointing, and there is more pointing in 6" quarries than in large slabs.

I think the takeaway is that something should be done, as distinct from nothing which is what a concrete floor amounts to.

Ivor

I think the rationale was probably that the rest of the extension was built with a DPC so the extra cost of a full limecrete slab would be wasted. You’re right about the floor breathing through the pointing though. I should have mentioned that our 9” pamments are pointed with lime mortar, even over the concrete portion of the slab though that area was for colour matching rather than breathability of course.

I fully agree with your ‘takeaway’ point!

 

[88v8]

My last house had "rubbers" and a soldier course for the window sill built c.1843

Nah. The head is an arch. A flat arch, but an arch.
And the sills are what usually manifests as 45 degree cut bricks.

A flat arch has a slight curve. It looks 'right'. We readily perceive what looks right and wrong even if the difference is so slight we're scarcely aware of it.
After all, columns, entasis.

Ivor

 

[Abi Cott]

My last house had "rubbers" and a soldier course for the window sill built c.1843

Nah. The head is an arch. A flat arch, but an arch.
And the sills are what usually manifests as 45 degree cut bricks.

A flat arch has a slight curve. It looks 'right'. We readily perceive what looks right and wrong even if the difference is so slight we're scarcely aware of it.
After all, columns, entasis.

Ivor

If I understand MatthewC correctly, that's what he was talking about when he was describing "rubbers". He will have to confirm though, I'm just guessing.

 

[MatthewC]

My last house had "rubbers" and a soldier course for the window sill built c.1843

Nah. The head is an arch. A flat arch, but an arch.
And the sills are what usually manifests as 45 degree cut bricks.

A flat arch has a slight curve. It looks 'right'. We readily perceive what looks right and wrong even if the difference is so slight we're scarcely aware of it.
After all, columns, entasis.

Ivor

If I understand MatthewC correctly, that's what he was talking about when he was describing "rubbers". He will have to confirm though, I'm just guessing.

Thanks, Abi, I think you understand my point exactly . The picture on my blog shows a "flat arch" (to use Ivor's term) which is barely noticeable, and I suggest that this style from the 19th C or before (?) is what generated the more modern style of soldier courses.

 

[overlander matt]

Thanks for the discussion points on this one. I've never previously had anything against a soldier course but it has got me thinking and looking about as I drive around! I am interested to know what alternatives exist to soldiers over a 3m opening for a bifold door. On the front of the house there are some nice rubbed arches but elsewhere there are plain arches above the windows.

Back to the materials and the interface between the old and new, I can confirm that our architect was not keen on the use of limecrete and specified concrete - the default option no doubt. A detail I have not mentioned is that we plan to raise the floor level by 25cm in the Victorian ground floor part of the building to match the Georgian part and new extension. This raised floor will be adjacent to the extension's floor slab. As we live in an area at risk of flooding this provides a useful extra buffer should the flood waters come our way in future... At present the Victorian rooms have vinyl floor tiles laid over 1cm thick bitumen. The floor certainly does not breath but I see no signs of damp in this area - therefore, with a concrete floor, should I expect any different behaviour? It's fair to say too that the walls won't help the breathability coated as they are in Artex. I was thinking about a compromise between laying some limecrete floors in the old house and a concrete slab in the extension.

When it comes to the brickwork on the extension, is there any advantage to using reclaimed bricks over a new 'heritage' brick? The bricks won't match the existing building that closely as we have three different types of 'original' brick that we'll be building onto. In terms of the mortar, I guess it will be a modern sand and cement which needs to be a white colour to match the lime mortar elsewhere. Has anyone any experience of trying to match a cement mortar to lime mortar?

Thank you.

Matt