Lime finishes: what's the point? Pressure difference in storm conditions in a changing climate

Review
Dear Authors and Editor,

Thank you for the opportunity to review the revised version of the manuscript.

In my opinion, the manuscript has been substantially improved compared with the previous version. The authors have addressed the main issues raised during the earlier review, and the revised manuscript is now much stronger in terms of structure, clarity, and overall argumentation.

I have only a few remaining comments. Apart from some minor typographical corrections, the section numbering should be checked carefully throughout the manuscript. In addition, some explanations currently placed in the Introduction appear to be more closely related to the methodology. For example, The paragraph beginning with "To investigate this mechanism, a purpose-built wall with a window opening—normally used for building-craft training at the Scottish Lime Centre Trust, (SLCT) Charlestown..." would be more appropriate in the methodology section. Similarly, some of the information presented under Section 1.3, “The aim of the experiment,” seems to relate directly to the experimental design and methodological procedure, and could therefore be moved to the relevant parts of the methodology section.

Once these minor issues are addressed, I believe that the manuscript will be suitable for publication.

Sincerely

Note:
This review refers to round 2 of peer review.

Review
I have read the new version in comparison with the marked up version I sent in with my initial review, checked the other reviewer's comments, and think that the authors have responded well to both sets of reviewer's comments. I'm sure that some of the points we made have not been addressed, but the paper now reads much better and is clear and of interest to the readers of the journal. Some grammatical oddities have crept into the final version (e.g. actualistic instead of actual) and I would suggest that the authors give one final, detailed check of the manuscript before submitting the final version. This does not merit 'minor revisions needed' but is important.

Note:
This review refers to round 2 of peer review.

Review
General comments
This is an interesting paper which investigates a very important topic – how best to protect historic buildings from climatic extremes. The focus on vernacular architecture in Scotland and driving wind, air pressure provides a good example of a more general problem. The paper is innovative in using historical research to explain the current state of vernacular buildings, and in combining this with experiments designed to assess the success of different conservation strategies on such buildings to protect them in future.
I think some improvements to the structure and flow of the paper will make it of interest to readers with an interest in historic building conservation under future environmental conditions. Given the broad scope of the journal I do wonder whether the paper is too specific, but I leave that up to the editor. In my opinion, some judicious improvements to the paper could make it of more obvious appeal to a wider audience as I summarise below. I have also added some notes to the pdf which pose some more specific questions and make some more specific suggestions (which I will send to the editor as I don't appear to be able to add them to this form).
Some suggested improvements
My main feeling on finishing reading the paper was that there were two distinct parts which were not well integrated. The material on the history of harl finishes in Scotland and their implications for the vulnerability of vernacular buildings today seemed very separate from the material which poses the hypothesis that pressure differences are a major risk factor for deterioration and then sets out the results of an experiment that builds on this hypothesis and compares the response of harling vs pointing to pressure differences.
1. Title: Lime finishes: what’s the point? Pressure difference in storm conditions in a changing climate. This is a bit vague and unspecific for a general environment journal. It also illustrates the two-fold division of the paper which I think could be improved upon. My suggestion would be for one sentence – which could be posed as a question – which illustrates that you are talking about lime finishes on historic buildings.
2. I suggest you make the aim and objectives of the paper a bit clearer and more specific – this might help integrate the two parts of the paper that I identify above. I’ve added some notes about this on the pdf.
3. I think the experimental design is under-explained. In particular:
a. Could you include an image/ diagram of the experimental set up showing the scale of the wall and the locations of the monitoring?
b. What order did you run the experiments in? Did you use one wall only and apply multiple finishes sequentially or did you have more than one wall with different finishes? Did you first run pointing simulations and then apply harl/ sneck harl? How large was the wall?
c. How long did you leave the mortars to cure before running the experiment?
4. The conclusion section is very short and doesn’t really fulfil the aim as stated at the beginning of the paper. What is the key take home message to the readers of a broad environmental issues journal?

Note:
This review refers to round 1 of peer review and may pertain to an earlier version of the document.

Review
Report
MS Title: Lime finishes: what’s the point? Pressure difference in storm conditions in a changing climate

This study critically examines the widespread conservation practice of applying recessed heritage joints in rubble stone buildings. It questions the assumption that the exposed aggregate appearance reflects original construction, suggesting instead that it is largely the result of long term weathering processes. Through a controlled experiment simulating storm conditions, with particular attention to pressure differentials across the building envelope that drive water ingress, the research evaluates and compares the protective performance of this pointing approach with that of full lime coatings.

Although the study addresses these questions through experimental investigation, several key aspects, some of which are outlined below, require further refinement and improvement.

Abstract:
--“To date, the default repair method for rubble stone buildings has been pointing, and the style employed is the heritage joint: a recessed joint with aggregates exposed.”
..The abovementioned statement is overgeneralized. repointing has been one of the most common and routinely applied repair intervention. However, calling it the “default repair method” is an oversimplification. Please revişe your sentence accordingly.
“In an innovative experiment…”
..Here we are in abstract section, so it will be usefull to define the “innovative experiment”

Introduction:
--It is strongly suggested to demonstrate some examples of harl and pointing styles for those who are not familiar with these techniques, especially the international readers, and your statement regarding the applications

--The statement regarding carbonation (especially: “…to produce a robust mortar without the use of additives.”) is overgeneralized, there can be addititives e.g., organic binders, pozzolans, to improve workability, durability, and setting properties.


---“wall widths generally reduced from approximately 1.5 m to 600 m.”
..This statement contains a critical error, as reporting wall thicknesses decreasing to "600 meters" is implausible; please reconsider the data and revise it accordingly.

--- The fig. 2, provides only a qualitative representation of wind induced pressure distribution. To improve clarity and reproducibility, a colorbar scale with defined minimum and maximum values and the represented variable, for example pressure or pressure coefficient, should be added and explicitly described in the caption.
..Additionly, the internal pressure modeling assumptions and the pressure concentration at lintels and sills should be quantitatively indicated or supported by localized detail views,in caption or on figures
--- “The mortar used in Experiment 2 was an HMM mortar mixed with Melville Gates sand and Shap high calcium kibbled quicklime at a rate of 3-part sand and aggregates…”
..please define HMM
---The central claim that the recessed joint profile is a result of weathering, rather than original intent, is a significant hypothesis that requires robust material evidence to move beyond speculation.
..For this argument to be convincing and form a stable foundation for the study, the manuscript would benefit from incorporating direct physical evidence.
This could include:
.. Visual documentation showing weathering patterns consistent with the systematic loss of a former surface coat within the recessed joint,
..Material analysis identifying traces of original coating/rendering residues within the joint recesses or demonstrating a weathering gradient,
..Examples of irregular mortar lines that follow the degradation of stone edges, indicating the joint was once flush.

-- “The HMM mortars showed visible shrinkage cracks at all stages: building, sneck harl and harl.”
“In the NHL trial, shrinkage cracking was not visible and only became apparent when bubbling water at the perpendicular joints was seen during the pressurised trial from within the chamber.”
..To support the observations above, it is recommended to provide a collection of figures illustrating shrinkage cracks, bubbling etc.

-- The Discussion section requires revision as it fails to fully interpret the experimental results, inadequately integrates the statistical analyses, and lacks a thorough comparison with relevant literature.
--The findings are not convincingly synthesized into a coherent narrative, and the derived conclusions and practical recommendations remain weak.
--A restructured discussion should comprehensively address these points by explicitly linking all results back to the research questions, contextualizing them within existing studies, and concluding with strong, evidence-based guidance for conservation practice.

Note:
This review refers to round 1 of peer review and may pertain to an earlier version of the document.