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RICS Expert Witness Reports

Boundary Disputes





This concerned a blocked walled detached house that was under construction. The cavity had been retrospectively insulated with foam. The mixing of the foam creates heat and it is also injected at high temperature. In this instance the temperature was too high and the heat from the foam caused all of the walls to expand resulting in vertical fractures at all of the corners both internally and externally. Method of repair was to insert stainless steel tiles in to a number of the horizontal mortar joints crossing the fractures and bond them in with an epoxy resin. The report prepared for the Court follows the photographs.


A general view.

Typical External Fracture

Typical External Fracture

Typical External Fracture

Typical External Fracture

Typical Internal Fracture


Typical Internal Fracture

Typical Internal Fracture


Typical Internal Fracture


1st March 2022


Mr Patel

2a Pine Tree Road





Dear Sirs


2a Pine Tree Road Leicester


Thank you for your instruction to investigate fracturing of the above property following the installation of BASF Walllite CV100 Insulation by British Insulation Services


Conflicts of Interest


I have not acted for either party before.




I am Steven John Macgregor Butler, a Member of the Royal Institution of Chartered Surveyors. I qualified in 1992 and have in excess of twenty years’ experience of surveying property for defects in the Midlands area. CV attached at Appendix 1.




The property is a house two storey house with a frontage of about 1.0m and a depth of about 9.0m that is constructed of cavity block walls with pitched tile roof. The walls and roof were apparently in-situ by about August 2020 after which construction was paused due to Covid restrictions.


In August 2021 the cavities were insulated by the injection of the Walltite CV100 insulation which is a ‘closed cell, polyurethane foam insulation injected as a liquid that rapidly solidifies.


At this point the building formed vertical crack between 5mm and 10mm wide at its four corners as shown in the Photographs at Appendix 2. There are fractures of both the inner and out leaves of the blockwork.


A characteristic of the application of the polyurethane foam insulation is that it heated to install it the heat being used to control the setting rate of the foam.

It also produces further heat as it sets.


Although the quality of evidence is likely to require further examination by the Court it is apparently admitted by the manufactures that the insulation can cause buildings so crack although they would normally expect and cracks to be of a hairline nature. See letter at Appendix 3




Vertical fractures of type seen at the property can have two causes these being heat of shrinkage of an over strong mortar mix.


The fracturing was first noticed by the operatives installing the insulation and they were sufficiently alarmed to seek the advice of BASF. There is no evidence that the building had cracked before this date.


I would thus consider that this entirely rules out the possibility that the fractures were cause by an over strong mortar mix as the building had been in-situ for a year without fracturing. Such cracks would be expected to be almost immediate. The mortar would largely have cured within about one month.


Vertical cracks can also be caused by temperature gains in a building from sunlight. However, such cracks almost always occur on the south or west elevations of a building as the building become hottest in the latter part of the day. I believe that such cracks are unknown on the interior of an unheated cavity wall building.


To form the cracks in all four corners on both the inner and out leaves of the block is consistent with there being a temperature rise of the whole of the building.


I believed that the only facture that can have caused this is the application of the spray foam which is known to be applied under heat and produces heat as it sets.


Likely causes are that the injection equipment was set at too high a temperature of the mix of the material comprising the foam was incorrect causing a particular hot reaction.


Remedial Works


In order to ensure that the building is stable and to prevent fracturing of the internal and external finishes the blocks will have to be tied together. This can be achieved by installing stainless steel ties set in to an epoxy resin across the vertical fracture set in every second horizontal joint.




There is no mechanism other than heat from the application of the spray foam that could cause the building to crack vertically at all four corners.


The cracks will require stitching together with stainless steel ties set in an epoxy resin in the horizontal mortar joints that cross the fractures.


These types of works are hard to cost. It is suggested that quotations are sort from a number of contractors based on a specification for repair to be supplied by a structural engineer.


Statement of Truth


This report is prepared in accordance with the Royal Institution of Chartered Surveyors Expert Witness Practice Statement.


I Steven JM Butler DECLARE THAT:


1. I understand that my duty in providing written reports and giving evidence is to help the Court, and that this duty overrides any obligation to the party by whom I am engaged or the person who has paid or is liable to pay me. I confirm that I have complied and will continue to comply with my duty.


2. I confirm that I have not entered into any arrangement where the amount or payment of my fees is in any way dependent on the outcome of the case.


3. I know of no conflict of interest of any kind, other than any which I have disclosed in my report.


4. I do not consider that any interest which I have disclosed affects my suitability as an expert witness on any issues on which I have given evidence.


5. I will advise the party by whom I am instructed if, between the date of my report and the trial, there is any change in circumstances which affects my answers to points 3 and 4 above.


6. I have shown the sources of all information I have used.


7. I have exercised reasonable care and skill in order to be accurate and complete in preparing this report.


8. I have endeavoured to include in my report those matters, of which I have knowledge or of which I have been made aware, that might adversely affect the validity of my opinion. I have clearly stated any qualifications to my opinion.


9. I have not, without forming an independent view, included or excluded anything which has been suggested to me by others, including my instructing lawyers.


10. I will notify those instructing me immediately and confirm in writing if, for any reason, my existing report requires any correction or qualification.


11. I understand that –


a. my report will form the evidence to be given under oath or affirmation;


b. questions may be put to me in writing for the purposes of clarifying my report and that my answers shall be treated as part of my report and covered by my statement of truth;


c. the Court may at any stage direct a discussion to take place between experts for the purpose of identifying and discussing the expert issues in the proceedings, where possible reaching an agreed opinion on those issues and identifying what action, if any, may be taken to resolve any of the outstanding issues between the parties;


d. the Court may direct that following a discussion between the experts that a statement should be prepared showing those issues which are agreed, and those issues which are not agreed, together with a summary of the reasons for disagreeing;


e. I may be required to attend Court to be cross-examined on my report; and


f. I am likely to be the subject of public adverse criticism by the judge if the Court concludes that I have not taken reasonable care in trying to meet the standards set out above.



STATEMENT OF TRUTH I confirm that I have made clear which facts and matters referred to in this report are within my own knowledge and which are not. Those that are within my own knowledge I confirm to be true. The opinions I have expressed represent my true and complete professional opinions on the matters to which they refer. I understand that proceedings for contempt of court may be brought against anyone who makes, or causes to be made, a false statement in a document verified by a statement of truth without an honest belief in its truth


Yours faithfully


Steve Butler


SJM Butler