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This question is posed in relation to responses to an early question about whether lay-people could assess whether a building is safe to re-enter after an earthquake.

My original response was that it could be risky for a lay-person (by which I mean not a civil or structural Engineer) to do such an assessment, but after some reflection, I wondered whether a very experienced Engineer (CEng PEng) could do an assessment remotely, using photographs sent by a lay-person on the ground.

About eighteen months ago I did building assessments of garment factories in Dhaka as a response to the Rana Plaza collapse. Doing these assessments made me realise that even a very limited (in terms of time and investigation) inspection could enable worthwhile judgements to be made.

As as experienced Engineer who has worked on many buildings (large and small, low-rise, high-rise, concrete, masonry, timber), I very much know what I am looking at with respect to the structural safety of a building. I am also aware that a lay-person can see a crack and either

a) panic b) be far too cavalier about significant structural flaws.

So, if an Engineer were to inspect buildings from photographs, what could be a possible methodology?

1) Start with a description. Low-rise, high-rise, masonry, concrete. From a description, an Engineer could assess the level of risk. E.g. a high-rise building would impact more people if it collapsed. So, at this point, it could be that a remote inspection is deemed inappropriate.

2) Sketch location and topology. A building on a slope is having to deal with more onerous ground conditions and therefore might be put under more stress than a building on a flat site. There may be slope stability issues very locally to the building.

3) Ask the lay-person to take photos of elevations, floors, roofs and to put key dimensions on the photographs. For example, a masonry building has more inherent strength if cross-walls are frequent. A concrete framed building is often stronger if the floors are beam and slab construction as opposed to flat slab.

4) Ask the lay-person to take photos of any cracks over 3mm (or it could be 2mm, or 5mm); vertical cracks, horizontal cracks, diagonal cracks.

At this point, the Engineer might be able to conclude that the building is in very precarious state.

5) Ask the lay-person to photograph wall and floor/roof junctions, asking them to describe as much as possible what the support to each floor/roof is. E.g. is there a good bearing for a floor joist or concrete slab floor.

6) Ask the lay-person to measure floor thicknesses. For example, if there is a very thin flat slab spanning large distances, this might be a warning sign.

7) Ask the lay-person to judge whether there is any 'lean' or 'tilt'.

I am sure that there are many more questions that could be asked, so suggestions would be welcome.

The final point is that the Engineer needs to have the final say on whether a conclusive recommendation is possible or whether more measurements or photographs are required. It is unconventional to assess buildings from afar but could be appropriate in this situation.

This question is posed in relation to responses to an early question about whether lay-people could assess whether a building is safe to re-enter after an earthquake.

My original response was that it could be risky for a lay-person (by which I mean not a civil or structural Engineer) to do such an assessment, but after some reflection, I wondered whether a very experienced Engineer (CEng PEng) could do an assessment remotely, using photographs sent by a lay-person on the ground.

About eighteen months ago I did building assessments of garment factories in Dhaka as a response to the Rana Plaza collapse. Doing these assessments made me realise that even a very limited (in terms of time and investigation) inspection could enable worthwhile judgements to be made.

As as experienced Engineer who has worked on many buildings (large and small, low-rise, high-rise, concrete, masonry, timber), I very much know what I am looking at with respect to the structural safety of a building. I am also aware that a lay-person can see a crack and either

a) panic b) be far too cavalier about significant structural flaws.

So, if an Engineer were to inspect buildings from photographs, what could be a possible methodology?

1) Start with a description. Low-rise, high-rise, masonry, concrete. From a description, an Engineer could assess the level of risk. E.g. a high-rise building would impact more people if it collapsed. So, at this point, it could be that a remote inspection is deemed inappropriate.

2) Sketch location and topology. A building on a slope is having to deal with more onerous ground conditions and therefore might be put under more stress than a building on a flat site. There may be slope stability issues very locally to the building.

3) Ask the lay-person to take photos of elevations, floors, roofs and to put key dimensions on the photographs. For example, a masonry building has more inherent strength if cross-walls are frequent. A concrete framed building is often stronger if the floors are beam and slab construction as opposed to flat slab.

4) Ask the lay-person to take photos of any cracks over 3mm (or it could be 2mm, or 5mm); vertical cracks, horizontal cracks, diagonal cracks.

At this point, the Engineer might be able to conclude that the building is in very precarious state.

5) Ask the lay-person to photograph wall and floor/roof junctions, asking them to describe as much as possible what the support to each floor/roof is. E.g. is there a good bearing for a floor joist or concrete slab floor.

6) Ask the lay-person to measure floor thicknesses. For example, if there is a very thin flat slab spanning large distances, this might be a warning sign.

7) Ask the lay-person to judge whether there is any 'lean' or 'tilt'.

I am sure that there are many more questions that could be asked, so suggestions would be welcome.

The final point is that the Engineer needs to have the final say on whether a conclusive recommendation is possible or whether more measurements or photographs are required. It is unconventional to assess buildings from afar but could be appropriate in this situation.