A Way Forward (or a better Protocol)

1. A Way Forward(or a better Protocol) P.G. Biddle

2. Determining which remedy: • Persistent deficit (significant heave) • Underpin with full anti-heave precautions • Seasonal drying (predominantly) • Vegetation control • Fell • Prune • Root control • Underpin (if tree of sufficient value) P.G. Biddle

3. Information required: • Seasonal or Persistent deficit • Which vegetation is involved. • If vegetation control, proof of whether it has been effective. • Extent and duration of heave. • Extent of movement for partial underpinning. • Appropriate level of proof for situation. • Speedy resolution for house owner. P.G. Biddle

4. Efficacy of investigations. Prelim Assess Trial holes Soil Invest. Root Ident. Crack monit. Level Monit. P.G. Biddle

5. Preliminary assessment Pattern of damage Time of development of damage Probable geology (BGS survey). Proximity and type of vegetation If conclusion probably vegetation …… P.G. Biddle

6. Efficacy of investigations. Prelim Assess Trial holes Soil Invest. Root Ident. Crack monit. Level Monit. Seasonal or persistent def.   Which vegetation involved.     Whether remedy effective   Extent and duration of heave   Extent of partial underpinning.    Appropriate level of proof      Speedy resolution for house owner      P.G. Biddle

7. Other factors to consider: Ownership of the tree: Own tree Third party TPO or Conservation Area Value of the tree. P.G. Biddle

8. Value of the tree. LTOA use CAVAT Relevant to remedial options, not to extent of investigations If the owner values the tree, it is worthy of proper investigation P.G. Biddle

9. Other factors to consider: Ownership of the tree: Own tree Third party TPO or Conservation Area Value of the tree. Number of trees / shrubs P.G. Biddle

10. Essential Desirable Useful but not necessary Waste of resources Scope of investigations Value of tree(s) Owner ship Number of trees Level Monit. Crack Monit. Trial hole Root Ident. Plast. index Desic. autumn Desic. other Preliminary assessment sufficient Single Low Own Tree / shrub Many Single High Many Single Low Third Party tree Many Single High Many Single TPO or Cons. area Many P.G. Biddle

11. Application of level monitoring Only if needed Earlier!!!! P.G. Biddle

12. Application of level monitoring • Install level monitoring at first visit • Level distortion survey if possible • 2nd set of readings (after 6 weeks) : • Initial diagnosis of pattern. • Initial diagnosis of which tree(s) involved. • Put TP on notice. TPO application or CA notification. • 3rd / 4th sets of readings (after 12 / 18 weeks) • Confirm diagnosis. Update TP and Local Authority. • Consider need and location for soil investigations. • Decide on and implement action. • Continue monitoring to confirm efficacy. P.G. Biddle

13. Level monitoring with late notification 9 Confirm diagnosis 8 7 ) Action m 6 m ( 5 t n Claim notification e 4 m Confirmefficacy e 3 v Set up Initial diagnosis o 2 M 1 0 s O N D J F M A M J J A O P.G. Biddle

14. A Draft Protocol. In any situation where tree-related subsidence damage is suspected, level monitoring will provide the most relevant and cost effective method of investigation. If any tree suspected of involvement is deemed to be of value by its owner, level monitoring should be the primary method of investigation. It should be commenced at the earliest opportunity. Level monitoring on its own should usually be sufficient to: 1. Confirm that the pattern of movement is consistent with the influence of trees or shrubs on a clay soil. 2. Demonstrate the extent and spatial distribution of foundation movement and its relationship to any damage. 3. Identify which trees or shrubs are likely to be involved. 4. Determine whether there is a risk of long-term heave consequent upon tree removal. 5 If potentially relevant, identify the extent for partial underpinning. 6. Demonstrate whether remedial measures have been effective. Other methods of investigation, such as trial pits, soil investigations for plasticity or determination of desiccation, root identification, distortion surveys or crack monitoring are of secondary importance. They should only be necessary if there is any uncertainty in the interpretation of the results of level monitoring. The scope of any such investigations should be decided in the light of the ongoing monitoring results and designed to resolve that uncertainty. The results of level monitoring should be reviewed as each set of readings becomes available. Decisions on remedial action should be taken once the data is sufficient to show a pattern of movement consistent with the implicated tree(s) or shrubs, and then continued to determine the efficacy of the remedial action. The timing and duration of readings should be determined on such basis, and not to a pre-determined or fixed pattern. If applied correctly, in most situations level monitoring will avoid the need for other investigations, and will provide the most cost-effective, reliable and speedy resolution to the problem, to the mutual benefit of the home owner, tree owner and insurers.

15. In any situation where tree-related subsidence damage is suspected, level monitoring will provide the most relevant and cost effective method of investigation. If any tree suspected of involvement is deemed to be of value by its owner, level monitoring should be the primary method of investigation. It should be commenced at the earliest opportunity.

16. Level monitoring on its own should usually be sufficient to: 1. Confirm that the pattern of movement is consistent with the influence of trees or shrubs on a clay soil. 2. Demonstrate the extent and spatial distribution of foundation movement and its relationship to any damage. 3. Identify which trees or shrubs are likely to be involved. 4. Determine whether there is a risk of long-term heave consequent upon tree removal. 5 If potentially relevant, identify the extent for partial underpinning. 6. Demonstrate whether remedial measures have been effective.

17. Other methods of investigation, such as trial pits, soil investigations for plasticity or determination of desiccation, root identification, distortion surveys or crack monitoring are of secondary importance. They should only be necessary if there is any uncertainty in the interpretation of the results of level monitoring. The scope of any such investigations should be decided in the light of the ongoing monitoring results and designed to resolve that uncertainty.

18. The results of level monitoring should be reviewed as each set of readings becomes available. Decisions on remedial action should be taken once the data is sufficient to show a pattern of movement consistent with the implicated tree(s) or shrubs, and then continued to determine the efficacy of the remedial action. The timing and duration of readings should be determined on such basis, and not to a pre-determined or fixed pattern.

19. If applied correctly, in most situations level monitoring will avoid the need for other investigations, and will provide the most cost-effective, reliable and speedy resolution to the problem, to the mutual benefit of the home owner, tree owner and insurers. P.G. Biddle

20. Risk assessment P.G. Biddle

21. Castellain Mansions

22. Castellain Mansions Datum April 1995 Movement Sept 1995 P.G. Biddle

23. Risk assessment • With suitable data, one can identify overall degree of risk • But not which individual tree poses that risk. • So should we be trying?? P.G. Biddle