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

Saturday, 1 December 2012

In a nutshell

Some of you will know by now that I am moving on in the new year, to one of the oldest and most highly respected consulting engineering practices in the country (and who specialise in conservation). Yes, I will have to commute into London again, but so be it. This was too good an opportunity to turn down and I'm looking forward to jumping into the deep end again (best get revising over Christmas!).

Given the imminent move from RDT to Hurst Peirce + Malcolm , just in case it's my last scribble here, I thought I'd post a quick photo-essay of our most recent piece of involved conservation work; a shop unit in Chesham, Bucks. This was a particularly good example of a project presenting a range of issues facing the conservation engineer in practice. Conservation "in a nutshell" if you will, from an adjoining owner that wouldn't repair his own rotting timber frame wall (can't elaborate as Party Wall negotiations ongoing), to all manner of impermeable finishes, to a real mish-mash of iron, steel and timber alterations to unravel.

This Grade II listed, three storey building, according to the official listing dated back to c.1740, had been converted to a shop at ground floor in Victorian times (at which point the entire front fa├žade timber frame was removed and replaced with rendered brickwork) with the two upper storeys in residential use until the fairly recent past.

Our client had only recently bought the building freehold. Having been born there, he felt somewhat philanthropic towards the sorry state it was in, but was in for a bit of a shock when the repairs, estimated at £75k by his commercial surveyors, turned into a bill in excess of £250k once the full horror was uncovered.

Unfortunately, ill health put an end to any long-term plans our client may have had, but not before we were able to make the building weatherproof and structurally stable. (See annotated photos below)

Hopefully, I will be able to continue writing posts from time-to-time, but this will obviously depend on company policies and the amount of spare time I get.......

Photo from the 1920's (nicked from the Cheshammuseum.org.uk website). Our building is on the right-hand side of this old roadworks, yes, roadworks scene.

The entire roof had been covered in this "turnerised" coating: A reinforced bituminous sheet material, painted to try and match the old tile colour. Just laid straight on top of the old tiles. Presumably sold as a 'maintenance free' solution, I would personally like to shoot in the nether-regions whoever it was that allowed this to happen. Horrible stuff....

Leaks in the so-called protection coat in the rear valley gutter led (eventually) to the partial collapse of the roof structure (the point at which we got called in)....

..... but not before water had been penetrating the building fabric for many years (upper floors uninhabited even with retail premises at ground floor). A wide variety of fungi greeted us on our first inspection.

Not satisfied with trying to waterproof the roof, someone had also tried to waterproof the external walls with cement render too. Result: Complete loss of original timber framing in places where render had cracked, let water in, but not out again.

Took a while to figure out what was going on here. Eventually found an original lower purlin was being asked to carry the load of a more recent cross beam (installed to support original upper purlins instead of resolving actual racking roof problem) and had snapped as a result. Existing door frame below seemingly happy to carry all the load, one way or another....

An ingenious one-sided forged iron joist hanger. Probably would've been ok had the end of the joist not started to rot away.

Some of the steelwork used to support the original timber frame allowing the open space for the shop unit below. Although it looks quite puny, this back-to-back channel arrangement was found to be perfectly capable of supporting the required load from above.

As much as I hate to admit defeat, this particular original purlin had been so badly eaten away that even the historic  steel strapping wasn't enough to save it this time.

You can't always rely upon the description in a listing, as many buildings were not inspected internally at the time of original listing. As noted above, the listing states that the building dates from c.1740 - You should have seen the Conservation Officer's eyes light up when presented with the stripped back remains of what we agreed was probably a c.1550 hall-house. (Upper floors inserted during c18th, we think)

Here is more of the original timber framing with wattle & daub infill panels.

The saddest loss for me was the failure, due to rot, of one of the original tudor cross-frame principal rafters. Here are the remains being used to help model its replacement in new air-dried oak (lucky find by the carpenters at a local timber yard).

Despite the need to replace the one failed purlin, we found just enough guts left in this (and other) original wind brace(s) to be able to keep it.

Both supported purlins at the frame junction had rotten ends. Here the carpenters  are preparing a new oak shoulder  to support the scarfed ends of both purlins (cut back clear of the extents of the wet rot). Note also more original wattle & daub infill.

A new jowl-post fitted in the rear wall, before being worked down to size-match the original lost section (The valley gutter beam had also rotted beyond repair and it's replacement was to be fitted to the jowl in due course).

Finally sorted out the earlier noted mess of timber. New lower purlin and wind braces installed and existing cross beam now hung by specially forged steel stirrup strap.

After repairing the rear wall timber frame and brick infill, breathable wood fibre insulation boards are being fitted in readiness for a new lime render finish.

We completed the external shell and internal structural stabilisation works, but unfortunately at this point our client 's health deteriorated and he called a halt to the project. Sad to see the building up for sale before being able to get it back into use, but at least we have 'stopped the rot' quite literally and sincerely hope that a buyer is found soon to put the building back to use....

Thursday, 19 July 2012

'Wear & Tear' to Roofs: What I really said to The Sun

This is not a complaint, just a clarification.

So, only my second ever mention* in the national press. And in The Sun too! I appreciate Jane had a hard job on her hands editing a mass of information down to a few column inches. This is Wednesday's Cashflow feature story as it appeared (including my much condensed paragraph) revealing the impact that the current bizarre weather may be having on our buildings. The message got lost in the edit, so I thought  I'd post it here, in full.

The story goes something like this: Having seen this blog, Jane approached me for my thoughts on the new 'wear and tear' get out clause being adopted by some insurers, as highlighted in the case of the Stockwell (Will Self, et al) terraced houses parapet collapse, I replied as follows:-

"There is an onus on householders to maintain their roofs. Primarily to stop the rain getting in, but also from a structural adequacy perspective. There are three main things that can damage (or lead to damage of) the structure of a roof:

1. Adding weight that it wasn’t designed to carry (ie changing from slates to tiles, adding solar panels etc)

2. Not fixing roof leaks, which can cause rot/woodworm in the timbers.

3. Adding too much insulation and/or blocking ventilation to the roof space, which can also lead to timber rot/woodworm.

Ideally roofs should be regularly inspected for defects and those defects remedied asap. If you can avoid all three of the issues above, your roof structure will be fine.

But I do not believe that this should solely be in the hands of the owners and insurers should bear some responsibility when things go wrong.

Well maintained roofs can last for hundreds of years, if not a thousand or more (just look at our cathedrals).

“Diurnal drift” is something that occurs on a daily basis (to varying degrees) and well maintained roofs can quite easily cope with this movement as timber structures are inherently flexible. The main problem occurs when you introduce masonry (ie gable walls or parapets).

In my opinion, the primary issue with the Stockwell case was not roof collapse at all (you can clearly see the roofs still intact) but the collapse of the parapet wall which, I am guessing, was not securely tied back into the roof structure and therefore got pushed over when the roof ‘expanded’ in the warmer temperatures. (There are probably other structural issues at the base of the parapet, but I can’t comment on that). This lack of strapping masonry elements back into roofs is very common in old buildings."

I probably should have mentioned keeping gutters clear too, but was really keen to stress the point about masonry gables and parapets. Still, its a lesson for the future. Get even more precise and to the point! Well, it is The Sun, after all. Onward & upward....

(*- First ever mention:- Winning The Times Fantasy Cricket League - (stage 1) c.1995)

Sunday, 15 July 2012

Saved from the (Fireman's) Axe

Another little case study for you this time.

Now I'm not going to claim that we single-handedly saved this building from the wrecking ball, but it was under very real threat from some senior figures within the regional fire service. Its two main problems were firstly; it was starting to fall apart and secondly; it was not big enough to house the new fire engine being rolled-out across the county. The only thing in its favour was its position within a conservation area, but even this offered no guarantee of survival.

The building dates back to the late 1930's, when the land was gifted to the village by the local landowner. He also contributed to the initial construction costs (or so I am led to believe).

We were approached by the 'enlightened' County Council Estates Manager, who thought we would be best placed to help, given our previous project experience with him. Our original brief was really just to convince the fire service that it would be cheaper to repair and extend, rather than demolish and rebuild. On the basis we could refurbish, the works would need to include raising the roof, internal alterations, a new rear extension (to replace an existing portakabin) and all necessary structural repairs.

We initially thought this would be easy to prove, but the structural cracking was a bit of a worry. We got some ground investigation work done and this discovered that the station had no foundations other than the 8" unreinforced ground slab it sat on, with nearly 5m depth of made ground beneath. No wonder it was on the move (the site was prone to flooding, with the made ground suffering from repeated "washout"). These findings obviously increased the repair costs, but this was partly balanced by the fact that any new building would need to be on piled foundations.

Luckily, the granular nature of the made ground meant we were able to use grout injection techniques to strengthen and stabilise the soil. This added just under £40k to the project cost, but was cheaper, more sympathetic and a lot less disruptive than remedial piling. (We had initially approached Uretek, but the contractor eventually selected a slightly cheaper rival.)

Once out of the ground, the project went very smoothly, other than a slight wobble over building the new brickwork in lime mortar during deep midwinter. However, with the help of the over-roof scaffold and background heating (and some timely advice from the Scottish Lime Centre) things went as well as could be expected.

The big red doors caused us a bit of a problem as the specialist installers (no choice - pre-novated) insisted everything had to be fully plumb, even though the whole front of the building was tilted because of previous foundation movement. Again, this was overcome by a bit of creative thinking and a bit of new floor levelling grout. The finished result looks a little odd to the trained eye, but it was the best we could do. We had the last laugh though, as the door mechanism broke down in front of everyone at the 'Grand Re-opening ceremony!

Some annotated photos below:-

The Station as we found it, looking a little sorry for itself, with numerous structural cracks and a noticeable dip in one corner of the floor.

Just one of the cracks found in the front piers. Indicative of  differential settlement of foundations (or lack of foundations, it so transpired).

The largest crack, in the rear wall. Previous remedial works by council engineers included tie rods and angle straps, which unsurprisingly did not solve the problem - a clear case of not determining the cause, in this case, being foundation failure. 

Walls raised. Roof ready to be "lifted". Having worked tirelessly to source matching bricks and creasing tiles, the contractor (T&B Special Works) did a great job on raising the walls. Initially I was disappointed with the results, but that was in the artificial light within the over-roof. Once the walls were out in daylight, it looked much, much better. The timber roof joists were generally in sound condition, so we just reused them. (Some joists had soft ends where built into the walls, so the decision was taken to re-support on joist hangers, meaning we could save more of the original joists.

Despite specific instructions, one chap went at these joints with an angle grinder. Its not often that I have to physically jump in and stop someone working! Works went better elsewhere and after installing Helifix stitching rods (in a lime grout) the repointing made it look much better at the finish.

The piled raft slab just cast for the new rear extension. Needed due to the depth of made ground  noted above, Abbey Pynford did a good job for us here with their innovative driving 'mole' mini-piledriver. (The extension had to be constructed within existing brick retaining walls - just in case that was confusing you).

Internal alterations (in progress) to side rooms required. Not only was the new engine taller, it was also longer.

The rear extension 'Crew Room' finished and fitted out. A vast improvement on the old Portakabin.

The finished product. (Note: This is not the new larger engine).

Monday, 21 May 2012

Conservation Engineering for Engineering Students

You can thank students for this one. In particular, Charlotte Illsley ( @Concrete_Geek )

As far as I am aware, in the UK, right now, there is no mainstream education for budding building conservation professionals below post-graduate level, and no mainstream education in conservation engineering at all, so how on earth can young (and not-so-young) engineers get interested in this 'branch' of structural engineering (unless you are lucky enough to be working at one of the handful of practices that specialise in conservation)? I know this is something that Andie Harris (HSI/NECT) is looking into and hopefully something will come of it. A good start would be for universities to offer an optional module in refurbishment and conservation.

Well, I thought I'd help out by doing a 'bitesize' version of my first blog post and by coming at it from a slightly different angle for a different audience.

I had always taken Conservation Engineering to be a 'specialism'. This is still the case, since you can become 'accredited' in it and good on you if you are. You have proved yourself against a rigorous assessment process with your aptitude and experience. This accreditation enables you to work on major/capital projects for clients such as English Heritage, The National Trust and projects funded by HLF and the like. But (and I speak from a personal perspective here) there is no middle ground, no stages, no mid-term assessments. You are either accredited or you are not and then there is always the catch-22 of getting the necessary experience in order to become accredited if your firm does not have 'pedigree'.

Thinking about it from another angle, should it really be a specialism practised by a limited 'elite', or should it be a another tool in the box of every engineer? Clearly there are pros and cons both ways, but the current system means that one can remain fully ignorant of what is involved unless one goes specifically out of ones way to find out. This invariably leads to insensitive treatment of non-capital (lower grade and unlisted historic buildings, which still require the same level of care), where no specific conservation credentials are required. But lets leave that discussion for another day.

So, back to the point: What is Conservation Engineering? What makes a good Conservation Engineer?

The most important thing in my opinion is to be passionate about old buildings, how they were built, their history and saving them as a legacy for future generations.

Secondly, as there is no specific training as such, you need to be able to fully understand and appreciate conservation philosophy and then adapt your 'conventional' engineering skills to put that philosophy into practice. The modern definition of conservation is 'managing change' and the engineer will use his specific skill and experience to respond appropriately to any changes with minimal detriment to the historic or architectural significance of the building in question. In my book, this means doing nothing to the building unless you need to.

This is easier said than done. Even though a building may have quite happily stood there working for hundreds of years any changes/alterations to, or degradation of, the building fabric, plus changes to building usage or external/internal environment can break that fragile equilibrium. There are also 'business' factors to consider, such as insurance/risk management.

So, lets try and boil this down by taking a simple example (to keep this post to a manageable length), say an existing timber spine beam, approximately 200 years old and an original part of the building. A change of use will result in a change to the existing loading regime:

Firstly, we survey, collecting all the data we need to enable assessment: Sizes, span, deflections, species, condition (rot, insect attack, splits, shakes & twists, etc - utilising specialist surveyors if needed) - as hopefully, any engineer would. But after this, the 'conventional' (new-build) engineering approach diverges from the conservation path.

Design codes go out of the window. Old buildings were not designed to Standards but from experience handed-down by generations. We make an accurate assessment of what dead and live loads are likely to be, rather than plucking a figure out of the loading code. We use simple analysis to determine stresses and strains in the beam and then use our judgement to determine whether those stresses are too high or not (these cannot be compared to modern grade stresses as old timber is known to be much stronger than new) using working loads only (no place for factors of safety here, unless we judge that some extra bunce is necessary). If there is any doubt over the capacity of the beam, then load testing can be carried out in-situ to verify assumptions, particularly useful if you want to try to determine Young's Modulus. Repairs and/or strengthening, if deemed necessary will be considered in such a way that the conservation tenets are adhered to (conserve as found, minimum intervention, like-for-like, reversible, sympathetic) with a presumption that repair is always preferable to replacement, unless there are exceptional circumstances. Traditional carpentry timber repairs are also preferred, as opposed to introducing alien materials, but again this may not be possible if loadings/stresses are too high. We also quite often have to come up with more than one solution to a single problem in order to give the client or architect a choice. They like that.

The strengthening of an original oak beam using a central vertical steel flitch plate (invisible from below apart from where timber plugs cover recessed bolts). Strengthening was required in this case due to a significant case of wet rot damage at one end.
I hope this has given you an quick insight into the world of conservation engineering and that a few of you might take it a little further. Please do not hesitate to get in touch if you have any specific queries.

Some recommended courses:
The SPAB's 5-day 'Repair of Old Buildings' course, run twice a year.
'The Structural Repair of Historic Buildings' 3-day course at West Dean College, by Ian Hume and Terry Girdler.
Individual courses run by The Weald & Downland Museum, Essex County Council and others.

Some Recommended reading:
"The repair of Ancient Buildings" AR Powys (SPAB)
"Structural Repair of Traditional Buildings" by Patrick Robson (Donhead)
(Quite old now, some repairs involving cementitious materials, etc now out of favour)
"The Repair of Historic Timber Structures" by David Yeomans (Thos Telford)
"Structural Aspects of Building Conservation" by Poul Beckmann & Robert Bowles (Elsevier)
Numerous papers written by Ian Hume for The IHBC and Buildingconservation.com.
"The Repair of Historic Buildings" by English Heritage
"Appraisal of Existing Structures" by IStructE

PostScript: So, it appears that a handful of universities offer some sort of optional module in conservation. I would like it to be more. I should also mention the IHBC route to accreditation, a valid alternative for engineers too.

Saturday, 28 January 2012

Building Regs. & Listed Buildings

Apologies for the silence over the last six months or so, just been too busy to put anything together. I wanted to write this piece a while back, when it was a little more topical, but never mind.

We were recently involved in a project that had some similarities with Sarah Beeny's Rise Hall restoration, in terms of dealing with "the Authorities". In particular, Building Control.

I have been rather scathing about the "Beeny's Restoration Nightmare" TV programmes themselves, due to the unnecessary 'dramas' and lack of useful detail on the restoration process itself, however by-and-large I think what Sarah (& Graham) have achieved with the building is very good indeed. I would also point out that, as far as I have been able to decipher, there were never any issues with the Conservation Department (who were on-board with the project at a very early stage - and remember, simple 'repairs' do not require formal listed building consent, although I would recommend at least discussing any proposed work with your local Conservation Officer). The problems have revolved around the planning COU (change of use) issue and the subsequent Building Control "requirements" that kick in with some COU's. The 'retrospective' method of dealing with these issues really didn't help either.

Read all about what needs Building Regs approval here... http://www.legislation.gov.uk/uksi/2010/2214/part/2/made

We got called in quite late on this project in south-west London. Our client was already well advanced with converting the building into a day school/nursery, but the architect had noticed a significant dip in the lobby floor near the front entrance - so we got called in to have a look. Only after we had solved the problem and works were nearly complete did we then get hit with a load of 'conditions' from Building Control to resolve retrospectively (always a pain when you're not involved from the start). I shall now try and put prior & subsequent events into a nutshell:

Dating from c.1810, this Regency villa (Grade II) is only one of two remaining from a row of as many as 12 along this stretch of road. You can see its rather ugly new neighbour on the right, as well as the modern extensions to the left.

As far as Building Control are concerned, a COU into an educational facility is one of the most onerous kinds (as one might imagine), invoking the need to comply with most parts of the Building Regs. Doubly so if 'structural alterations' are also planned. It is part of the conservation engineer's role to try and limit the need and/or impact of these conditions when a listed building is involved, by developing reasoned arguments backed up by calculations where applicable, to avoid unnecessary and inappropriate works.

We were disappointed when Building Control would not treat this project differently from a normal 'school' in the conventional sense. Our day school was for a maximum of 75 3-11yo's spread over four floors. Not quite the same as Waterloo Road or Grange Hill is it? Anyway, the conditions that I had to deal with mainly related to Part A (Structure) & Part B (Fire). I left everything else to the Architect.

Initially, I had to figure out how this building worked and satisfy MYSELF that it was robust enough to do the job. Apart from some remodelling of partitions in the attic storey, the building was pretty much as original. The roof, an oddly proportioned 'M' shape, was never capable of fully supporting itself, so the remodelling of partitions had inadvertently changed the loadpath going down the building. This together with the cutting of a large archway into an original braced stud partition at ground floor, meant that a sizeable chunk of load was being supported on the lobby floor joists - thus explaining the excessive deflection. I decided, on balance, that some steel beams would be required to get the load back onto the brick walls of the basement. Headroom was tight, so the joists were cut to allow the steels to sit within the floor depth. Luckily for us, the basement ceiling was not original (and cracked to buggery in any case).

No structural alterations, as such, were made anywhere to facilitate the conversion of the building.

At this point, The Letter from Building Control arrived.....

Getting around the floor loading issues was relatively straightforward. Although the building had been built as a residence, it had been used as offices since at least the 1950's and I also did some calculations based on room usage data provided by the client to prove that live loads would not exceed 2.0kN/m2, as opposed to the 3.0kN/m2 required by BS6399 (and not to mention the real strength of joists that age, compared to their modern counterparts). Similar arguments re corridors and stairs (fire escapes) were luckily accepted without further question.

The one item I didn't get my own way on (completely) was disproportionate collapse. Despite my protestations, they decided that my new steelwork was an 'alteration' rather than a 'repair' - but I did manage to knock them down from a full tying scheme to just tying across the joists that had been cut (a bit of a waste of time as these joists were all spliced across the walls and not continuous in any case), and I did have to prove that the new steel beams were 'blastproof' but after some quick calcs using the reduced safety factors for 'accidental loads', we ended up just needing some bog-standard restraint straps. The client was a bit miffed as he had already replaced the ceiling by this stage, but was made a bit happier once he found out what we'd got away with.

The staircase was the last issue that needed resolving from a structural aspect. The original winding timber cantilever stair was still intact along with its balustrade. We had already decided that the low handrail and steep internal winding were not going to be particularly safe for younger children, so we bit the bullet and designed a new balustrade with infill panels to sit inside the existing and the posts were clamp-bolted to the stair risers so as to make the system fully reversible. The only downside was that this made the stair too narrow for the current Regs., but again, presentations of usage data (and a dose of common sense) persuaded the fire officer that congestion on the stair would be minimal and we had made the right decision overall.

I'm not going to mention Part L (thermal) here, other than to say that exemptions are still available for listed buildings and other solid wall buildings, though you may have to go though a few hoops to justify.

OK, sorry, quite a large nutshell there. Best I could do! I've tried to explain everything, but if you do have any questions, please feel free to 'comment' below. I'll leave you with a few annotated photos below:
The existing floor joists under the front lobby. Not really clear from this photo, but worst-case deflection measured at 100mm on a 3.5m (12ft) span.

Distortions a bit clearer here. This steel post had been previously installed where a floor trimmer beam had snapped. Slightly away from the area we were concerned about, but we took the opportunity to replace the beam and remove the obstructive post.

We tried everything possible to avoid using steelwork, but the load concentration was just too great. We got the CO onside and designed the steel so it could be lifted up to sit in between cut joists with minimal disruption. (and before you ask - no, the ceiling was not original)

The surviving original cantilever timber staircase. Had sagged a bit, but was still perfectly sound (having passed my 'bounce' test with flying colours.) Sorry no photo of the second balustrade, not been back to site to see it finished.

Not an optical illusion: The end of this original garden wall really does lean that much, primarily caused by a large tree on the other side. It remains uncracked (due to the flexibility that lime mortar gives) and is effectively propped by the later house wall. We left well alone. (The new arch in the foreground? - Just don't ask!)

However hard you try, things still slip through the net. Me: "I hope that's a lime render" - Chap: "Well, its got some lime in it" #FacePalm