[2023] UKUT 00282 (LC)

The structural engineers instructed by the parties had a much wider remit than the building surveyors. They were asked to consider, for all the structures at the property, whether damage had been caused by the works, including vibrations during construction. They were also asked to consider if damage was likely to be caused in future by the works, and to give recommendations for potential remedial works if appropriate. Finally, they were asked to give opinions specifically on the alternative assumptions that either the groundwater level at the site had risen, or had not.

The claimants instructed Mr Peter Corcoran BSc (Hons) CEng MICE, a chartered engineer from The Morton Partnership (TMP), who has over 25 years’ experience of inspecting and reviewing historic structures. As mentioned above, Mr Corcoran had previously advised the claimants and had provided them with a condition survey in August 2014. Observations in that report were updated in brief following a visit by TMP in August 2016. Mr Corcoran’s report, dated 20 May 2022, followed further inspections in December 2021 and February 2022. The report provided a tabulated comparison of observations on cracks and movement in 2014 (in the TMP and Ridge reports), in the 2016 update and following the 2021 inspection. Although the 2016 update contained only brief comments, and may not have been as thorough as the 2021 inspection, it is notable that many of the incidences of increased levels of cracking or movement in ground floor rooms were first noted in 2021.

The respondent instructed Mr Stuart Hookham, a chartered structural engineer from William J Marshall & Partners. He reviewed evidence available from earlier investigations and reports, including those of TMP and Ridge from 2014, and made an inspection in February 2022 with Mr Corcoran, before reporting his opinions in May 2022.

The engineers produced a joint statement dated 15 August 2022, in which they stated their agreement on a number of matters. It was agreed that the cracks evident in the house prior to the works, although unmeasured, were not considered to be structurally significant. They agreed there was evidence of some minor movements between 2014 and 2022, shown by an increase in length and width of some cracks and by identification of new cracks. Whilst those movements did not appear to be structurally significant, the full effects of the works on the fabric of the building may not have been realised in that time period if the level of groundwater had changed. The potential movements appeared to be greatest near to the stairs to the south-east (Footnote: ⁵)side of the property.

It was agreed that the methods of construction used in the works did generate vibrations, as evidenced by a technical memorandum on vibration assessment produced by CH2M, but that the recorded vibrations were not, or were unlikely to be, of sufficient strength to cause damage and/or movement to the property and associated structures. The one exception was Mr Hookham’s opinion that it was possible the damage to the drainage system between the house and the river, evidenced by drainage surveys before and after the works, may have been caused by vibrations or by direct impact during construction of the works. Mr Corcoran’s opinion was that damage to the drainage system was likely to have been caused by works traffic.

There was no baseline data of damp in the house prior to the works against which the engineers could judge whether the moisture content within the fabric of the house had increased since the works. Mr Corcoran noted that the surveyors had agreed that pre-existing areas of damp damage had increased in size, and deteriorated further, and that there were new areas of damp in the house. The engineers had read the reports of the hydrologists and it was Mr Corcoran’s opinion that the new areas of damp were likely to have occurred as a consequence of changes in the ground water levels. In Mr Hookham’s view it was unclear whether damp at the property had increased, although there was evidence that paint and plasterwork had deteriorated in isolated areas of damp between 2014 and 2022. In his opinion it was also unclear whether the underlying conditions that had led to this deterioration had changed between 2014 and 2022. It was possible that the amount of water entering the property had increased over that period, but it was also possible that the underlying damp conditions had remained constant.

The engineers agreed that the effect of the works on groundwater level at the site was a matter for the hydrological experts, but expressed their positions on the alternative assumptions that either Mr Evans was correct, that the works have caused the groundwater level to rise by 0.5 to 1.0 m, or that Mr Groves was correct, that the works have had no impact on groundwater level.

On the assumption that the groundwater has risen as a result of the works, the engineers agreed as follows as to whether that rise had caused damage:

“it is possible that damage may be caused to the [building] by increased and/or differential settlement of the foundations and/or an increase in moisture content in elements of the fabric that are in close proximity to the ground.”

However, the agreement is somewhat tentative. Unlike the surveyors the engineers were not confident in attributing existing deterioration to the respondent’s works. They agreed that the detrimental effect of an increase in moisture content would be likely to manifest itself gradually over a period of time, with the full effects not yet realised. They agreed it was not clear that all existing observed changes in cracking could be attributed to a change in groundwater level as there would be normal cyclical and thermal effects in a building of this age.

It was Mr Corcoran’s opinion that the movement in proximity to the stair was greater than would be expected from seasonal movement, likely to be attributable to a change in groundwater levels, and that some elements of the building structure had been damaged by additional areas of damp. That included load bearing masonry and possibly embedded timber members. Mr Hookham would not go that far.

As to future damage the engineers agreed:

“that the detrimental effects of an increase in moisture content in elements of the fabric … will likely not occur immediately but will instead likely manifest gradually over a period of time”

However, the engineers were able to agree a schedule of remedial works to be considered should it be established that groundwater levels had risen and that damage and/or movement had been caused.

On the alternative assumption that the works have had no effect on groundwater level, the engineers agreed that it is unlikely the works have had a material impact on the condition of the house and also unlikely that there would be a material impact in future.