A Little bit about me...

I'm a Structural Engineer, specialising in conservation, at Hurst Peirce + Malcolm in London. I don't wear tweeds, am not particularly "cultured" and I'm not that old, but I do care passionately about the conservation of old buildings. I am a Chartered Structural Engineer, a member of The SPAB (formerly on the founding committee of the reborn Berks, Bucks & Oxon Regional Group), a Friend of SAVE Britain's Heritage and have recently completed a PD Diploma in conservation at West Dean College, with a view to achieving CARE accreditation. I hope to give you regular updates on my trials and tribulations as well as some insight into projects I am involved with and things I believe in.

Be patient with me - I'm no writer and I'm normally up to my eyeballs at work........

All views expressed here are my own.

Hurst Peirce + Malcolm, Celtic House, 33 John's Mews, Holborn, London WC1N 2QL

07854 624692 - richardsalmon9@gmail.com

Sunday, 17 July 2011

'Built Heritage' Terminology for the Layman

I'm posting this, not just because of 'Restoration Home', but what has come out of a few separate conversations on both Twitter and in real life. For the purposes of this exercise, I am trying to gauge what the public at large think they will get when offered a TV show entitled "Restoration Home", so I would be very grateful if non-heritage bods could leave their thoughts (before reading this) as comments below. I would also ask if you would be happy with a TV programme that showed a building conservation project done properly, without any dramas - let's call it 'edutainment'? (I also welcome comments from Heritage peeps if you think what I'm about to say comes straight from my backside!)

During the kerfuffle about 'Restoration Home' last week (of which I was as vocally critical as anyone), alarm bells started ringing in the back of my head about the application of this word "restoration". As a member of the SPAB, I abide by it's manifesto (easier said than done at times), as penned by founder William Morris. The SPAB was founded in 1877 largely in response to a certain type of Victorian "restoration" that Morris and others objected very strongly to, namely to "restore" buildings to their perceived "original" condition based on nothing more than conjecture and using whatever materials came to hand that 'looked about right'.

I am used to the British Standard (BS7913) definitions, but as this is for the layman I wanted to look in the most obvious non-specialist place, so I grabbed a small dictionary (Oxford, concise), the sort of dictionary found in most houses across the land, and looked up some definitions:-

HERITAGE (n.) - What is or may be inherited, ones portion or lot.

So, our built heritage is something we have "inherited" and we have a duty to look after it until its time to pass it on to the next generation, and so on...

CONSERVATION (n.) from CONSERVE (v.t.) - Keep from decay or change or destruction.
PRESERVATION (n.) from PRESERVE (v.t.) - Save or keep from death or injury or loss or oblivion or desuetude or decay.

Now obviously on their own, these words can be confused with other things, so we have to put 'building' in front of either term ('preservation' is the current preferred word used in the US in particular, though that may be subject to change if certain Twitter convo's are to be believed). But they can be misunderstood (or maybe not?) to mean a museum-like status where all is 'preserved in aspic' etc.

However, I like to consider the new modernised definition of conservation to mean 'managing change' i.e. promoting minimal intervention, like-for-like and reversibility techniques where things do need to 'change' for whatever reason.

Now the big one:

RESTORATION (n.) from RESTORE (v.t.) - Give back, make restitution of, replace, put back, bring back to former place or condition or use, re-establish, infer and set forth the original state of,.... by rebuilding or repainting,..... reconstruct it conjecturally.

Now herein lies a problem. Reading between the lines we have more than one meaning here. There is 'good' restoration, where things are renewed because they need to be (from loss, accidental damage, fire, rot etc) and there is 'bad' restoration - the faux period detailing or losing layers of history, etc so despised by Morris et al.

If you also look up RENOVATION and REFURBISHMENT you get very similar definitions. Conversely, 'good restoration' could also be described as REPAIR.

Confused? You're not alone. I like to think each project can be located on a scale bar that has conservation at one end and restoration at the other. Any project that departs from this scale is being done wrong.

By the way, I am not going to mention CONVERSION or ADAPTATION here, that can wait for another day!

(Note: Definitions stolen directly from the Oxford English Dictionary, copyright whoever, blah, blah, blah.....)

Sunday, 3 July 2011

Phoenix from the flames

This Grade II listed barn in North Norfolk dates back, at least in part, to the late c16, but is now quite a complex of bolt-ons of varying dates. It has been partially converted for use as a private function room and is held under lease along with the adjacent, but separately listed farmhouse.

The fire started externally in the open-sided lean-to (cause remains disputed) and apparently lasted approximately two hours until extinguished by the Fire Brigade. During this time, the fire had spread into the main barn, damaging sections of the main barn vaulted roof (lower slope on fire side, upper slope on opposite side), as well as entirely gutting the lean-to roof itself.

We were appointed to design and project manage the reinstatement, liaising directly with the Insurance Loss Adjusters and local Conservation and Building Control departments.

On contacting the Conservation Officer, we were advised that so long as reinstatement works were "like-for-like" they would take no further interest. A little surprising I have to say. Perhaps he thought I knew what I was talking about! We did stick with the like-for-like philosophy as far as possible but had to deviate when an existing structural detail was found not to work, or in the case of the low level windows where we replaced some ugly 1980's windows with something more appropriate (seeking listed buildings consent as we went along, of course).

Fires can be devastating, but quite often, if caught early enough, apparent damage can look much worse than it is and much can be salvaged. Large old timbers for instance will char to a certain depth and then stop, with the charring zone actually protecting the sound timber beneath. We did calculations to prove that the chunky original trusses and some of the larger purlins were still man enough to work, even on a reduced section size. Once again, traditional construction proves to be quite resilient.

One thing to beware of though, is just how wet things get after the Fire Brigade do their thing. Some of the building elements took a full 9 months to dry out properly.

See below some annotated photos showing before, during and after repairs.

An archive photo of the barn before the fire. During the repair project it was discovered that the building had suffered a very similar fire event about 20 years before, meaning some elements of structure had already been replaced.

The lean-to roof completely gutted. The timber posts were charred, but could safely be re-used as the depth of charring was not significant.

Charring to lower slope rafters and wall plate. In most locations the wall plate was thick enough to save, but most of the rafters were too deeply charred to remain useful.

A shot showing the extent of damage within the main barn.

What we considered to be one of the original barn "windows". Unglazed, with hardwood rhomboidal mullions, it was very disappointing when we finally decided it could not be saved due to a combination of deep charring and historic beetle damage. We commissioned new slow-grown softwood matching frame with recessed glazing (as subsequently agreed with the conservation dept)

New slow-grown softwood lower rafter sections scarf-jointed to the remaining upper rafters and with renewed peg joints to connect to purlins. Note the de-charred truss rafter in the foreground.

The results of the first attempt at removal of charred and sooted timber surfaces. Started without our approval, we managed to stop this mechanical clean before too much damage was done! Always a philosophical argument whether to leave and consolidate charred timber surfaces as part of the building's history. The decision was made for us here!

A structural strengthening plate added to one truss member where charring added to the problems of this already weak section.

A repaired repair - this truss had previously been strengthened by splicing, but the fire damaged the splice so had to be replaced.

The main barn roof completed. New members blended into existing and given a coat of breathable stain. Ceiling relined in a light board with natural insulation and breather membrane added above. We also added a fire break between the main and lean-to roofs to ensure the same thing could not happen again.

Inside the lean-to: Our own 'forensics' showed that the monopitch trusses had the usual mortice and tenon connections, but were held together with Glasgow nails rather than pegs, so we replicated this. The repointed areas of wall show where the existing mortar had one a strange hue of pink and was crumbling away (flint and bricks showed no signs of damage). Note the new low level windows, a bit less "chunky" than those they replaced.

The lean-to from the outside, all new apart from existing posts and pantiles (reclaims used to replace those broken in the fire).

Sunday, 22 May 2011

Listed Buildings on a budget - Maintenance!

I am presenting this blog not because of what I had to do, but because of what I didn't.

This Grade II* listed almshouses building in NW Herts dates back, at least in part, to the 15th century and much of the original timber frame structure survives intact, despite many subsequent extensions and alterations.

Before work started. 

From the other side Early 1900's (?)

Almshouses depicted on the right hand side of the "village" sign.
Being owned and operated by the local church trust (and still in use for its original purpose), it is clear that a carefully budgeted and systematic programme of maintenance and repair down the centuries has avoided the need for extensive and expensive repair events usually brought about by long periods of negligence. As a result, hardly any structural repairs were needed from me.

This is not a perfect example by any means, but it seems the bulk of the problems it has suffered have been the result of either external environmental factors, or previous well-intentioned, but flawed, repair techniques (using inappropriate non-breathable materials). One example of these external factors resulted in the need to replace large sections of the original sole plate and stud feet along the front elevation (not part of our brief), undoubtedly due to the closeness of the building to a busy road and the tarmac pavement tight to the building face. (I believe the new sole plate is now protected by a sacrificial lime render skirt and a drainage channel).

The old adage "A nice hat and a good pair of boots" still applies to all buildings. In essence keep new moisture out of the building whilst letting internal moisture escape.

Regular clearing of gutters and downpipes and checking for splits in flashings and slipped slates/tiles etc, will ensure that water cannot get into the building from above.

Keeping ground levels around the building low and permeable (with drainage if necessary) will normally avoid damp issues at ground level.

When considering "improvements", make sure that breathable insulation, plaster and paints are used so as not to trap moisture within the building fabric.

Other tried and trusted maintenance tips: Paint windows and doors regularly. Stop vegitation from climbing on building faces (use trellising if you have to). Keep trickle vents and air bricks clear to maintain internal ventilation. (I could go on, but fuller checklists are available from other sources, particularly your local council's conservation department).

Regular maintenance will save an awful lot of money in the long run.

Please see annotated photos below showing a few things we did have to deal with.

This old purlin had broken its back (some time ago) where connected to a wind brace. We just fitted a new secondary timber purlin above the old, to provide a "splint".

A previous cement based face repair here has accelerated the decay of the timber behind. Luckily the decay had not gone too deep so we were able to effect a "piecing in" face repair in timber. 

This gable leans outward quite significantly, but timber frame structures are incredibly resiliant when compared to their masonry counterparts. No structural repairs needed here apart from the addition of a couple of wind brace timbers to abate racking in the rafters. The brick infill between gable frame members also turned out to be tied-in and stable.

From another angle. See the gable lean relative to the scaffolding.

This chimney has developed quite a bow. This is usually due to both external weathering/frost action and internal sulphate attack. We decided it was going to be ok for quite a long time so just did some repointing and asked for ongoing monitoring.

This previous timber cover plate had acted as a water trap, accelerating the decay of the timber beam behind. Again, luckily the decay was not too deep and we were able to bolt on a new face section.

Sunday, 17 April 2011

A Cautionary Tale

The Old Manor House in Cholesbury, Bucks, is an unimposing little brick cottage that hides a big secret (although the name is a bit of a clue). This Grade II listed cottage sits at the foot of Cholesbury Camp (Iron Age hill fort) and is considered to contain two bays of a much larger timber framed manor house/manorial court building dating from the 16th century. (I am hoping that @wallstroker will be given the chance to investigate this further). None of the ground floor timber framing remains, so the 9" brickwork here is loadbearing, but the first floor and roof framing are original and largely intact, so the brickwork at this level is primarily just cladding.

The Old Manor House - as existing
I was initially called in with building works already underway (extension), to give a second opinion on another Engineer's report advising that the existing bowing gable wall would need to be taken down and rebuilt (On inspection it was clear that this wall had already been rebuilt at least once before). The experienced builder had raised concerns over the necessity of the proposed demolition and the client obviously wanted to avoid the cost of rebuilding if at all possible. Quite unbelievably, the local Conservation Officer had seemingly accepted the Engineer's report on the most flimsy basis; that the wall was "unstable". But, other than some additional tying-in for the new wall, no other works were recommended in this area.

The "offending" gable wall.

On my first site inspection, I really didn't think the wall looked that badly out of alignment, but could see where the centre of the bow was located and then went about trying to find out why this had occurred. The first noticeable defect was a large separation crack between the gable wall and the chimney breast. This separation was at its worst at about first floor ceiling level and narrowed above and below this point. The next-most obvious defect was a strange oak corbel detail springing out of the corner of the chimney breast and apparently providing support to the original oak spine beam. A third defect was discovered up in the roof space. After marvelling at the original arch-braced central roof frame, I discovered that the original oak collar to the end frame at the gable wall had effectively rotted away where embedded into the chimney breast, leaving the purlin ends without support and thus applying load to pockets in the gable wall brickwork. There were also very shallow foundations (concrete) under the rebuilt gable wall.

So, by now we had a number of possible causes. I then undertook a plumb survey of both wall and chimney breast, which confirmed my earlier visual inspection, that the wall was only borderline unstable and could easily be tied back into the structure. Further analysis of the plumb survey results showed that the prime suspect to be the loading of the outer corner of the chimney breast, had caused a slight inward bowing of the breastwork, leading to a much larger complimentary outward bowing of the gable wall (the two not being effectively tied together).

Having found the problem, the solutions were relatively straightforward. Result: One happy client with a slightly less light purse!

The annotated photos below show some before, during and after repairs, but in essence, the moral of this tale is that one really has to get to the bottom of the problem, before suggesting a solution. Had the other Engineer just had the wall rebuilt, the same thing would have happened again, over time, with the new wall.

There are still too many old buildings being worked on by architects and engineers without the right attitude and/or experience, so just a quick plea to homeowners and developers to think twice before appointing your next design team.

As an engineer, mainstream philosophy says it's much easier to condemn something than to save it. That's where conservengineers come in.....

Part of the original framing visible at first floor.

Original arch-braced roof frame, purlins and rafters - still sound, even if they've moved about a bit down the years.

The gap between chimney breast and gable wall. Lovingly papered over by the previous owners.

The existing oak corbel detail. When we uncovered the extent of the structural damage to the original beam, the reason for the length of the corbel became clear. I'm sure a well intentioned, but an ill advised structural solution.

The spine beam from above. The steel flitch plate allowed us to invisibly "extend" the beam span so the load is carried directly onto the back of the chimney breast and gable wall. (Note: the timber section at the top of the pic is a new make-up piece to replace previously lost material)

A little steel assembly up the loft to provide support to the end of the purlin and ensure roof loads are applied onto the eaves level beam as originally intended.
As an aside, I was asked to asses the load capacity of the existing ceiling/loft after the loss of a large section of existing lime plaster. It transpired that excessive deflection (under imposed load) of relatively poor quality scantling joists had sheared off the grips between laths. The client was keen to utilise the loft space, so an independent deck was installed above the original ceiling. 

The beam repairs completed. The lowered section of ceiling is as original and signifies an historic infilled staircase.
The cottage, with extensions and repairs (very nearly) completed. The bowing gable wall was retro-fitted with ties into the existing chimney breast, first floor and roof construction, along with some bed joint reinforcement (in a lime grout) above and below the existing windows where cracking had occurred.

Saturday, 12 March 2011

Our Georgian Adventure - Part 3

Welcome back to the Dunham Estate. This time the Gatehouse, built c1800 and located at the entrance to the estate some 400 yards away from the Lodge and listed by curtilage alone. As you can see this is a very small hotchpotch of a cottage loosely in the "Gothick" style with brick and flint walls and a pantiled roof. Almost unbelievably this cottage was still occupied by an old tenant (a bit of a hermit, but a very nice man - he had grown up on the Estate, where his mother had been in service at the Lodge).

This project was undertaken with a different local contractor, who whilst espousing conservation experience while tendering, showed very little of such during the works. A short leash was definitely required here! I'd like to think that by the end of the project, we had taught him a few things.

As before, I was acting as lead consultant and worked closely with the local Conservation Officer to achieve an acceptable result within a reasonably tight budget.

In order to make the cottage a little more habitable, it was decided to knock the two tiny bedrooms into one less small one and remove the badly damaged rear chimney breast/stack and latterly added concrete-floored pantry to create a reasonably sized kitchen/diner.

The estate gardener is due to take up residence shortly.

The Gatehouse as we found it. Roof and windows leaking badly and some foundation movement.
Two of the three chimneys close up. In a very sad state due to weathering and internal sulphate damage (and some very poor previous repairs).
The chimney breastwork corbelling from triangular to square within the loft space. Some cracking had us worried about stability, so reluctantly we had to introduce some steel strutting to improve the situation.
Some quite severe cracking in the more modern (c20) rear extension. After a year of monitoring and some soils analysis, movement was found to be ongoing, partly due to tree root action, but mainly because of very shallow foundations and seasonal moisture changes. To avoid the upheaval of underpinning, Uretek ground grouting was utilised beneath the existing foundations.
The existing brick floor as found. Whilst in part saturated and crumbling after years under  non-breathable vinyl flooring, we were determined to save this integral feature of the original building. We were additionally hindered by the Client's maintenance team removing one whole room's worth before we even got on site!
Imagine our surprise when we found this leaded window behind a tin sheet, which we believe may have been salvaged from an old chapel somewhere. This has always been a blank window so all a little bizarre. On the advice of a specialist conservator it was decided not to try and remove the window for repair so we have left it in-situ behind a new tin sheet with a photographic record to be left in the finished cottage.
We were also slightly surprised to find this intact cast iron grate behind the existing plaster. We knew there was a double stack so were expecting to find a fireplace, but not this!
Some of the windows were worse than others. Repairs were done in the workshop where possible, but two of the windows had to be fully replaced, like-for-like.
We also found this dilapidated brick shed in the garden. The walls were in reasonably good nick so the Client allowed us to bring this back into service too.
After lots of digging we found the original brick culvert under the estate access road. This was strengthened with a polypipe liner and the ditches re-dug as part of the estate-wide HLS funded drainage works.
The timber roof structure was found to be in surprisingly good condition with only minor repairs required to rafter ends and a couple of the dragon beams. Along the rear wall of the extension it was agreed to introduce a proper eaves overhang, as the previous eaves detail was very poor and had allowed water to penetrate into the top of the wall.
The reconstructed chimney stacks. The loss of the rear stack meant that we had just enough sound original bricks to complete the works. We used an NHL2 lime mortar here just to give a bit of extra durability (lime putty mortar used elsewhere). The precedent for the pots was taken from the remains of one broken gault terracotta piece found in the ditch. Internally the stacks were lined with EML and lime parging.
The early shenanigans with the brick floors meant that we ended up having to lift all. We therefore took the opportunity to install "insulated" limecrete floors throughout, achieved via the use of LECA (lightweight expanded clay aggregate) both as a subbase and as the large aggregate within the limecrete itself. No, the membrane is not a dpm, it's a breathable terram geotextile which helps to bind the LECA subbase.
The removal of the rear chimney breast left this purlin unsupported. We utilised steel angles to extend the span onto the (as yet unbuilt) new bathroom wall. the purlins were then encased in matchboarding to suit the existing detail. A new timber beam was installed beneath the existing beam here also, due to the loss of the pantry wall. (Yes, that is cellotex you can see. Didn't stay there long!)
Plastering underway. Two-coat lime plaster - scratch coat with hair, finish coat without. Note the matchboarding to the sloping ceiling to match the existing.
Brick floor relaid onto limecrete slab with sand bedding and jointing. Floor then "sealed" with a breathable polish that I was given a recipe for (beeswax and turpentine). We just about managed to salvage enough bricks from other parts of the estate to complete this.
Nearly done. Walls limewashed, old fireplace ready to be opened out. Existing doors retained and repaired, even though only about 1.6m high. When it came to heating we had a good headscratch, but at the end of the day the only sensible solution was this woodburner with back-boiler to feed the four radiators - one per room. Low capital cost and ready fuel supply on site. We made sure we chose one with a good slow-burn time so that reasonable ambient temperature could be maintained for long periods.
Et voila! The cottage finished. Ground levels slightly lowered and gravel strips installed to perimeter to help with drainage. (This photo is pre-snagging. Not happy with some of the flint panel pointing - now sorted!) Note the use of glazed (black) pantiles on three sides with red pantiles on the rear slope and catslide - all original, reused.
Having insulated roof an floor, we successfully argued with Building Control that the breathable solid walls did not need to be improved. We also commissioned some de-mountable secondary glazing for use in the winter months.
And finally, the shed brought back to life. Needed some brick stitching and new roof timbers, but otherwise quite simple. Another rarity saved.