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, 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).

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