|The Old Manor House - as existing|
|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.|
|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.|
|The beam repairs completed. The lowered section of ceiling is as original and signifies an historic infilled staircase.|