Scaffolding for Historic Buildings

Kim: Good afternoon, everyone, and welcome to today's Technical Tuesday webinar. My name is Kim Rochard.  I'm the structural engineering team leader at Historic England. Today's webinar focuses on scaffolding for historic buildings. The webinar follows the publication of Historic England's Scaffolding for Historic Buildings Best Practice Guidelines, which is now available to download from the Historic England website. The guidance provides an overview of the approaches and design issues that need to be considered when scaffolding or other temporary works is required for work to a historic building or structure. It's intended for building professionals and contractors involved in maintenance and repair projects, as well as planning and conservation officers involved with scaffolding proposals in a historic context.  

Bridget Drake-Wilkes and Alex Evans are both senior structural engineers within Historic England's structural engineering team. Both have been involved with the production of the new guidance note. So, before we start, we're really keen to know the composition of our audience today, and invite you to take part in the poll that hopefully you can see on your screen now. Excellent. Just give me one more second. Thank you very much. Finally, from me, there will be an opportunity to ask questions at the end of the presentations. Please just put your questions in the chat on the left-hand side of the screen. And I'll now hand it over to Alex. Thanks, Alex.  

Alex: Okay. Thank you, Kim. So, I'm going to share this  presentation with Bridget. I'm going to do the first two sections, and then we'll take two sections each as we progress through. So, the introduction to the guidance that Kim introduced you to. So, historic buildings and scaffolding are generally two completely separate disciplines, and they mainly exist separately. So, this guidance is required because of the interface between the two. Although the interface is a small element of each, there is a great potential for harm to the historic building in this zone. This harm can be significant, and it can also be irreversible. So, this guidance is to manage the interface and reduce the risk of harm to the historic asset without compromising the function of the scaffold. It's just worth mentioning the guidance isn't for scaffold design, and it's not a guidance note on historic building conservation.  

So, the guidance was previously published about 30 years ago, under English Heritage, when they produced a guidance note, Scaffolding and Temporary Works for Historic Buildings. And earlier this year, Historic England published a new guidance document for scaffolding for historic buildings. So, how are heritage structures different? Why do we need specific guidance for heritage structures? So, temporary work designers and contractors are not necessarily experienced in historic structures, and heritage professionals aren't always experienced in temporary works. So, the golden rules, before we start, are early engagement and good communication, so that both parties understand the needs and constraints of the other. There are two main types of protected heritage assets.  

Generally, they fall under listed buildings and scheduled monuments, which have two different levels of protection. So, when we're looking at listed buildings, to undertake work on a listed building which is beyond maintenance and like-for-like repair, you need to have Listed Building Consent from your local authority. This includes any proposed works which affect the character. If in doubt, you should check. It's worth remembering the whole of the building is listed. So, if you had, say, a listed country mansion, and you just wanted to fix some scaffold to a plain brick wall or the back of a service yard, you would still require Listed Building Consent. And it's also worth remembering that the listing also applies to curtilage structures. So, these are independent structures within the curtilage of a listed building, and they usually require consent. And Historic England do do a separate guidance document on curtilage structures.  

Now, there are exemptions. There are five church denominations within England which don't need to apply for Listed Building Consent for certain of their buildings. This includes the Church of England, the Roman Catholic Church, the Methodist Church, the Baptist Union of Great Britain, and the United Reformed Church. However, they do have alternative procedures to the Listed Building Consent, and they may well be more onerous. Then we come on to scheduled monuments. While some change may be possible, with scheduled monuments there is a presumption that they'll be handed on to future generations in much the same state we have found them today. So, to undertake any work on a scheduled ancient monument, you require Scheduled Monument Consent. Now, this can be above or below ground. And these applications go directly to Historic England. And there are no exemptions for Scheduled Monument Consent.  

So, when we talk about the interface between an historic building and scaffolding, what we really mean is the point of contact. So, because of their heritage significance, potential points of contact, both planned and unplanned, need to be considered in advance, and they need to be managed. Every point of contact is a location of potential harm. So, this needs to be approached in the same way as any other risk assessment using the ERIC method of Eliminate, Reduce, Inform, and Control. So, points of contact can be at ground level as well as against the building. So, where there's no direct contact, a scheduled monument can still be affected. If you have high loads at the base, it can damage buried structures and archaeology. So, the scaffold footings should be specifically designed to avoid damaging historic substructures. So, any sharing of information regarding archaeology and constraints is essential, and this highlights the importance of collaborative working between all parties. So, now I'll pass you over to Bridget, who is gonna do guidance.  

Bridget: Thanks, Alex. Just before I start on guidance, I briefly want to touch on legislation. The primary legislation for scaffolding is the Health and Safety at Work Act. The secondary legislation relevant for access scaffolds is the Work at Heights Regulations. This is intended to prevent death and injury caused by a fall from height. And general access scaffolds provide a means of working at height whilst preventing falls. This regulation is prescriptive in terms of the inspection regime of access scaffolds to ensure the safety of the workforce. When a scaffold is not being used for access, i.e. protection from the elements, or to support a structure, the relevant secondary legislation is the provision and use of work equipment regulations, which- where the inspection regime is specified as at suitable intervals.  

The Health and Safety Executive is Britain's national regulator for workplace health and safety. The HSE publishes a wide range of information, including a brief guide to the Working at Height Regulations. The Health and Safety Executive's advice on scaffold design and erection refers designers and contractors to the National Access and Scaffolding Confederation Guidance. The NASC is the UK scaffolding industry's trade body, which publishes guidance on all aspects of scaffold design, management and procurement. The design most relevant to historic structures is listed here. TG20 is a design and operational guide to good practice for tube and scaffold fitting, scaffolding. A TG20-compliant scaffold is designed by using predetermined layouts, avoiding the need for a bespoke design with structural calculations, as electronically generated compliant sheets replace these.  

Bespoke designs should be produced for complex scaffold structures even when they are TG20-compliant. This ensures the scaffold is feasible and fits around the structure, including buried structures, whilst also providing guidance for its erection. All nonstandard scaffolds need bespoke design with structural calculations and drawings. In addition to TG20, the other one we're going to draw on later is TG4, which relates to drilled and cast-in anchors. TG20 defines an independent scaffold as one bay wide. Although referred to as independent when taller than two scaffold lifts, it needs to take lateral restraint from the building for its stability. The alternative to this is a bespoke scaffold, the design of which relies on other methods of stabilisation. In this photograph here, the lowest lift is an unboarded pavement lift to provide through access on the pavement.  

And then there are two more lifts above, making the criteria of more than two lifts per scaffold. On the garden elevation, restraint has been provided by buttressing scaffold tubes, and a return tie along the pavement elevation. On the pavement elevation, there is a return tie along the garden elevation, and additionally there is one fixing at the right-hand end at the top lift to provide the additional restraints. Where a scaffold is not being used for access, the inspection and maintenance regime should be specified by the temporary works designer. If a scaffold is likely to remain in place beyond the involvement of the contractor installing the works, a clear understanding is required between the client and the temporary works designer to achieve a balance between the design, frequency of inspection once the contractor is no longer on site, and the consequences of deterioration between inspections that would require maintenance to ensure the continued performance of the scaffold.  

In the photograph here, the scaffold was installed in the mid-1990s, and as the surrounding area is closed to the public, and the small workforce briefed not to go near the wall, it is inspected monthly. Aluminium scaffold tubes were selected, as they are more corrosive-resistant, and sleepers were used as sole plates to assist with load spread from the kentledge, and to provide a greater tolerance to decay. Throughout the intervening 30 years, the inspections have led to maintenance in the form of renewing of connections, scaffold boards supporting the kentledge, and sole plates. Design and procurement. Pre-construction information is a requirement of the CDM regulations. As part of this, the contractor and scaffolding subcontractor should be briefed on the aims and expectations for the scaffold, and precautions to eliminate damage to the historic structure. 

It should be clear where the fixings to the historic structure are permitted, and if so, what type of fixings and what locations are acceptable. Other constraints should be stated as clearly as available knowledge allows, for example the presence of buried archaeology or voids, the need to keep a pavement or highway open. The scaffold brief, in most cases, is prepared by the contractor, and guidance is available as to what should be included. Typically, the brief should clearly define who is responsible for each element of the temporary works design. This is particularly important at the interface between the scaffold and the historic fabric to minimise possible damage. Responsibility for design of the scaffolding foundations must also be clearly identified. Scaffold design is usually undertaken by the scaffolding contractor or their designer in the contractor's mobilisation period.  

For more urgent or complex scaffolds, the design may be procured in advance by the design team to increase certainty both in terms of cost and if it can be built with the constraints specified. If this is undertaken, it should be made clear that design responsibility passes to the contractor when appointed, so that they can modify the design to suit their method of working. On receipt of scaffold drawings, it's the responsibility of the permanent works designer to check the leg loads and the adequacy of the bearing ground, tie types and load to be transmitted to the structure, and whether the structure can withstand this load, butting loads, including ensuring there is adequate protection, and if it's a freestanding scaffold, what the anticipated sway is to ensure that there is sufficient clearance to the structure. I'm now handing back to Alex for practical considerations.  

Alex: Thanks, Bridget. So, practical considerations. Where possible, the scaffold should be completely independent and avoid contact with the historic structure all together. So, this is an ideal starting position. But in many cases, this won't be possible. And where it is impossible, early engagement with a conservation officer or Historic England inspector should be established to discuss options, locations, and details of contact points. Contact points tend to have different purposes, and some can be eliminated easier than others. The conservation officer or inspector would advise what supporting evidence or documentation may be required, so you need to allow enough time to engage with the consultants or specialists that you may need to appoint. For example, if you need to do a load capacity of the assisting structure, or if you need to do a Heritage Impact Assessment, you need to allow enough time for the consultants to undertake any inspections and provide that documentation.  

So, contact points which you might not be able to eliminate. The first one is temporary works. So, this is generally where a historic structure needs support. So, in this case, it's usually unavoidable that the historic structure will need to bear onto the scaffold. If this is the case, you should use appropriate packing materials to protect the structure. Any fixings that you may need to put in should be removable, reversible, or in the worst case, repairable. For scaffolding at higher levels, you should utilise back propping to ground level to avoid imposing additional loads onto the historic structure upper levels or any suspended floors. Another contact point may be where the scaffold requires support, so supporting a scaffold by bearing onto a historic structure should be avoided wherever possible. But there will be occasions where it's the only viable option.  

For example, if you have space constraints, or where doing otherwise might compromise essential repairs. You should avoid point loads directly onto the historic fabric. Any loads should be distributed, and the structure protected with suitable packing. Any fixings should be removable, reversible, or in the worst case, they should be repairable. And if you do need to make any repairs, you should have a pre-agreed plan for the repair, to the satisfaction of the conservation officer or the inspector. So, where you have a scaffold that needs to butt against an existing historic structure, this is typically where the access scaffold relies on the historic structure for stability or vice versa. It's important to protect the historic structure by packing the end of the tube. In its simplest form, you can use plastic end caps, although these can still cause damage, as they are point loads.  

A higher level of protection can be achieved with timber packers with rigid foam or sections of carpet, as in the top photo. Individual tubes should be able to be moved back to access the face of the structure. For example, if you need to do repointing works, or stone indent repairs. You should never locate butt tubes against any projecting features such as carvings, decorative stonework or gargoyles, or any other features which could be easily broken off. Any projections or delicate features you do have should be protected in advance. So, another contact point type is ties. So, these are used where the scaffolding is relying on the historic structure for stability or vice versa. You should really consider alternative methods first to avoid tying if possible, such as buttressing or kentledge.  

Drilled ties are an absolute last resort and should be avoided wherever possible. An alternative to drilled ties include return ties. So, this is where the scaffolding is taken around the corner of the building and restrained one or more bays beyond the return. You can do through or lip ties, such as the top photo. This is equivalent to a standard duty tie under TG20. They generally pass through window openings to bear onto one wall face, or to clamp both wall faces together. If you have glass or a window, this should be carefully removed for later reinstatement by a conservation joiner, not a scaffolder. Openings need to be sealed against weather and against unauthorised access. Lastly, you have reveal ties.  

So, these are short sections of scaffold tubes with a screw jack at one end, and wedged across a window or door opening. They rely on the friction between the masonry packs and steel props, and provide the equivalent to light duty ties. The TG20 recommends that no more than half of facade ties should be this type of reveal tie. They must be frequently checked for tightness, and so are rarely appropriate where scaffolding is likely to remain unmanaged for a long period of time. And lastly, we have drilled fixings. So, drilled fixings should only be considered where there is no alternative, or no alternatives have proved viable. They must be justified, and a statement supplied to explain why a less intrusive alternative is not suitable. If they're absolutely unavoidable, their numbers should be kept to a minimum. You should try and use removable ties, such as a plug tie, and avoid resin fixings.  

And the only exception really for resin fixings is where a maintenance scaffold might need to be erected in the same place periodically over a number of years, in which case it may be acceptable to install permanent sockets, and these can be grouted or bonded in place and sealed with a cap, allowing fixing bolts to be inserted whenever the scaffold is needed. You should locate drilled fixings as sensitively and as discreetly as possible, so ideally into joints and away from significant architectural features, and especially if going into a joint, you can load test if you're not sure about the capacity. You should consider the risk of rust jacking where the scaffolding will be in place for a prolonged period of time. An early engagement with a conservation officer or inspector is essential. Further guidance about the drilled fixings and compatibility with different substrates is provided in the TG4 Anchorage Systems for Scaffolding.  

So, let me come on to kentledge. So, this is a dead weight to resist, wind uplift or overturning loads, and it's usually a preferred method of stabilisation because it doesn't intrude into the historic fabric. So, it eliminates that high-risk point of contact against the building. Kentledge can comprise metal weights, precast concrete, blockwork, water containers, or sandbags. But you do need to consider if the kentledge could be accessed or stolen. On historic sites, the main consideration is the effect on buried structures or archaeology. Any weight needs to be distributed so it doesn't cause damage, and this includes the delivery and removal of the kentledge. Where you've got water containers, you need to think of the disposal of water when it's no longer needed. So, they shouldn't be emptied directly onto the ground because this might damage buried artefacts or buried structures. And you also need to consider the risk of damage from freezing or vandalism, if they can be accessed.  

So, resisting the elements. All scaffolds should be earthed to protect users from electric shocks. But do remember that if you're driving anything into the ground on a scheduled site, you need Scheduled Monument Consent. Historic buildings often need coverings on the scaffold, like an over-roof, for example, to allow for drying out, or to create the right conditions for curing of mortars or renders. This should be highlighted at the early stages, because the scaffold will need to be designed for high wind loads. Historic buildings can often contain a lot of timber which is not fire protected, and is therefore vulnerable to fire. Scaffolding itself can also be a fuel for a fire, and it also provides access to enable arson. So, you should consider fire prevention carefully, and ensure that measures are taken to prevent unauthorised access as far as possible.  

If you have a large over-roof scaffold or a large scaffold, you need to consider how rainwater will be disposed of to avoid saturating the ground and potentially damaging below ground structures or archaeology. And then, looking at the duration of how long the scaffold is going to be there for. Scaffolding on historic structures can often be in place for long periods of time, especially where they're providing temporary support, where the building is drying out, or where funding prevents work progressing. So, you need to allow for longer-term management. You need to consider inspections. Any scaffold needs to be inspected periodically to ensure it's safe and stable. It should also be inspected after any serious storms or potentially damaging events. You need to think about security.  

A scaffold can provide access to intruders. You may need to take measures to prevent unauthorised access and to minimise the risk of damage if intruders get in undetected. There's corrosion and decay. Timber and steel elements are both vulnerable to deterioration when exposed to weather for a long time, so they may need protecting, replacing, or upgrading. Fixings are particularly vulnerable, and they may need to be upgraded to stainless steel. You need to think about the wind loads. The wind loads will need to be assessed as a permanent structure, not temporary, and therefore will be higher. This can affect the design of the bracing, the tie loads, and the foundation design, which will all need to be reviewed. So, looking at avoiding contact altogether, we can think about alternatives to scaffolding.  

Is there another way of doing it? So, consider alternatives which avoid the need for contact points between scaffolding and the historic building. There's UAVs, which are unmanned aerial vehicles, commonly known as drones. These are a quick and safe means of undertaking a visual inspection of high-level or difficult-to-access areas. Ladders, hop ups, or podium steps. They are a quick means of accessing areas above head height, but their time in use is very limited. There's scaffold towers, which are a temporary means of access, and they usually have integral stability, so you don't need to fix into or butt against the building. But again, they're for short term usage. Rope access by specialist contractors is becoming more common. But if you do use this method, just remember that fixing anchor lines will require the same permissions as if you were fixing ties with scaffolding, and then you've got MEWPs or cherry pickers, mobile elevated working platforms.  

Consider the access and leg stability. The loads for some of these machines can be quite high. They can be very heavy. So consider the possible risk to below-ground structures or archaeology. If you want to track something across a suspended floor, you should do a load capacity check. There are a wide range of options for sizes and weights. So, we'll just look quickly now at the scaffolding erection and dismantling. So, this is the period of time during the scaffolding process which probably carries the highest risks to the historic building. The risk really is from impact damage during erection and dismantling. So, you should really do a risk assessment at an early stage. The principal contractor, a scaffolding contractor, should be briefed on the significance and level of care expected, and you should consider temporary protection to vulnerable areas.  

Toolbox talks to the workforce should be given to relay information to everybody who's involved, and you may need an enhanced level of site supervision to help control the risk. If there are any changes made to the erection and dismantling plan, this needs to be included in a review to the risk assessment. So, you need to think about routes. Delivery routes for vehicles. They can be quite high-risk. So, consider your use of bollards, barriers, and signage. When you are moving scaffolding from the vehicle to the scaffold location, you need to carefully plan to minimise the risk, including in tool box talks.  So, use barriers where needed, and any alterations against the plan should be included in the risk assessment. I'll now pass you back to Bridget for the next section on security and access.  

Bridget: Thanks, Alex. As previously discussed, scaffolding can provide unintended access for intruders.  Where there is space, fencing  or hoarding should be installed to prevent access to the scaffolds. When you're in a streetscape, as in the bottom right-hand picture, when the scaffolding is not in use, the ladder should be removed, or locking ladder guards fitted. Similarly, do not build lower lifts if access to these levels is not required. It's also important to consider access for the occupants in terms of the privacy of the occupants. Whether ties that require the windows to be left open is acceptable. But also in terms of maintaining far escapes, both for the building that you're considering and adjoining buildings. So, in conclusion, scaffolding provides access to build, maintain, and repair buildings and structures, including historic buildings.  

The terminology ‘independent scaffold’ does not mean freestanding scaffold. One bay wide access scaffolds need lateral restraints when it is taller than two lifts. If a scaffold designer is not familiar with historic structures, they will use TG20's standard details, and take restraint from the building with butts and drilled fixing ties unless they're adequately briefed instead of drilled ties, restraint for scaffolds can be provided by return ties, buttressing with additional bays, through lip or reveal ties, making the scaffold a bespoke scaffold. However, these alternatives may not always be appropriate due to other constraints, e.g. the footprint of the site, the duration that the scaffold is going to remain in position, or whether the building is occupied, as is more common with repair. If drilled fixings are unavoidable, the permitted location should be identified and agreed before the scaffold is designed, ensuring the appropriate consents can be obtained prior to commencement on site. As mentioned at the beginning, the key to a successful project is early engagement, good communication, and all parties understanding each other's needs and constraints. Thank you very much.   

Kim: Have you got any specific fixing typologies which you have found particularly effective? Minimally invasive/reasonably reversible?  

Bridget: I can go for that one. There are a number of different fixings, and some are smaller and therefore more reversible and can be located in joints. But often, with the smaller fixings. You then need more of them to be able to resist the loads that need to be carried. So, it's a balance which is specific. It varies from project to project. 

Kim: Super. Sometimes tying to the building is unavoidable. TG4 recommends tying into brick units rather than mortar joints. Is there another technical standard to apply to support the tie in to mortar joints to defend the conservation focused requirement to avoid harm?  

Bridget: TG4, my understanding was it does also talk about locating fixings in mortar joints, or one can do it by load testing the joints to get certainty as to the load capacity.  

Kim: Are there any particular risks to consider for scaffolding used inside a building? It's a slightly more general question.  

Alex: Yeah. Probably the biggest risk inside a building is during the erection and dismantling phase, where you're moving the scaffold tubes. You've got a lot less space to manoeuvre in and out. And that's where your biggest risk is probably from accidental impacts. So, that's why you need to plan your routes carefully. Possibly move any movable vulnerable items. And yeah, the toolbox talks are really important there so the people moving the scaffold understand the risks. And then anything that can't be moved that is particularly vulnerable, consider protecting it, putting packing or something on it.  

Kim: Are there any specific concerns regarding historic buildings for scaffolding to have public access?  

Bridget: I know what you mean. This is sort of high level viewing platforms and everything. The standard that's required for protecting the workforce should be fairly equivalent, but we don't know the particular details. We're not scaffolding experts.  

Kim: How does the structural condition of a historic building influence the choice and design of scaffolding? In your experience, what are the most common challenges when working with older or fragile buildings?  

Alex: I think probably not fixing into them wherever possible. That's usually the first... Not only because it causes damage to the historic fabric, but where you've got a building that's particularly in poor condition, the capacity of your fixings is- unless you do load tests, it's going to be quite questionable.  

Bridget: Also, particularly if you're looking to scaffold a chimney or something that's very slender, it probably isn't able to withstand the load that the scaffold is expecting, that it can apply to provide stability to the scaffold. So, you need an alternative means.  

Kim: Any comments on temporary roofing, as it goes hand-in-hand with this project? So, I think Alex sort of covered this when you talked about over-roofing  and things like that, didn't you?  

Alex: Yeah, I mean, it depends what the over-roofing is for. I mean, if it's there to enable a building to dry out, that's when you think about long duration, regular inspections, you've got your higher wind loads that are usually a quite a big consideration when you're looking over roofing. Yeah. Things like that.  

Kim: Another one on fixing into mortar joints, but, I think we've already talked about that with the load test, you can quantify the capacity of the mortar joints and specify the fixings accordingly. Would you consider making it part of the planning to insist that temporary works designs are carried out before main contractors tender for the works?  

Alex: That's probably quite project-specific maybe, because... I mean, every project is different. Yeah, I'd say that's very fairly project-specific.  

Kim: Depends on the project, scaffolding, and temporary works. Yeah. Can ground conditions such as soil bearing capacity affect the scaffold design?  

Bridget: Yeah. It doesn't affect the scaffold design. What it affects is that interface that we kept talking about between the scaffold and whatever it bears on. You should be able to... Someone needs to determine what bearing capacity the ground has, and therefore what load spread beyond a standard scaffold base is required to not exceed the bearing capacity of the ground.  

Kim: Yeah. Thanks, Bridget. Do either of you have any examples of structural reinforcement needed before scaffolding is installed? We've got a structural engineer asking a contractor to prioritise brickwork repairs internally before the erection of scaffolding.  

Bridget: This goes back to what we were talking about earlier with fragile buildings, and that whole thing of, if you are putting the scaffold up to repair something that's very vulnerable, you can't do the repair first because you can't get the access, if that makes sense. So, I guess that's what it's referring to.  

Kim: It might be one of those situations where if you've only got a small area that you need to do some quick work on, that you might look up scaffolding alternatives before you look at the scaffold itself. So things like cherry pickers, MEWPs, depending on what your building is. Possibly rope access. That might be one of those occasions where that's more appropriate than using scaffolding.  

Kim: Thank you. Do you generally need a specific scaffold design, or do some structural engineers design scaffolds? And this is one that we get asked a lot.  

Alex: No, you go for it, Bridget.  

Bridget: It's fine.  To be honest, you really need a scaffold designer or a temporary works designer, because the TG20 that we'd be referring to is kind of the Bible, and if you're someone who's not using it all the time, you're likely to miss something. And it's also a very expensive document, so it's unlikely that general structural engineers are likely to have it.  

Alex: I was also going to say as well that if you go specifically to a scaffold designer, anything when it comes to making adjustments or needing to do an element of bespoke design, they're going to be in a much better position to know what alternatives are and what options you might have.  

Kim: Brilliant. Thanks, Alex. Have you come across any situations where putlog scaffolding has been the preferred or most beneficial solution?  

Alex: No.  

Kim: If a scaffold requires a heavy duty designation to take heavy loads of stonework or brickwork, then will scaffold fixings through the structure be the primary preferred method?  

Bridget: It's just the same. So, TG20 allows for that. The spacing between the fixings is increased. So, as Alex mentioned, you have standard duty ties, but the frequency that you need the fixings into the structure is more for a greater rating. So, it doesn't affect the approaches, just the number of fixings.  

Kim: Do you have any advice on determining loadings on historic structures where the building construction can't be determined, for example a castle where the wall core material is unknown?  

Alex: I think that probably just comes down to experience of working with traditional materials. You tend to get a feel for roughly how much things weigh. But I think collaboration, like we said, early in engagement, early collaboration, there will always be other parties and other people who know things that you don't in terms of, you know, the conservation officer or the inspector might have more knowledge on the materials it was built from. So, I think just talk to as many people as possible, even- sometimes we go on site just talking to the custodians, and they can show us quite a lot of information about what was built when, where they sourced material from. And from that you can get an idea for how much stuff weighs. So I would say, don't be afraid to ask as many people as possible. There's no such thing as a stupid question.  

Kim: Do you have any advice for coordinating scaffold erection with the presence of bats and/or active bee colonies?  

Alex: Talk to your ecologist.  

Kim: Well in advance.  

Alex: Yes. Absolutely. Well, in advance. And stay friends with the ecologist.  

Kim: I suppose it could come down to what... you can only erect scaffolding at specific times of year. And that kind of thing, couldn't it?  

Alex: So yeah, it depends what kind of roost it is, it depends if it's a hibernation roost or a breeding roost. That's why this, again, comes back to this early communication, and good transfer of knowledge between the different parties. You know, as engineers, we're not ecologists. So, they're going to know things that we don't. And it's all about everybody understanding where everybody else is coming from.  

Kim: This is a good one. Regarding monitoring scaffolding after installation. If not thinking of storms, what timing would you recommend to check? Sort of, three months, six months, etc.?  

Bridget: For access scaffolds, the recommendation is every seven days or after a significant event, whether that's a storm, or an impact with the scaffold, or that sort of thing. Even if it's not being used as access, you may want to introduce that sort of caveat. Or if you notice something looks wrong about it, it probably needs checking.  

Kim: Are you aware of any problems with getting a contractor to take on responsibility for a very complex scaffold design?  

Alex: I think, again, that comes down to good project management. So, if you know you've got a complex scaffold design, if you're talking to contractors in the early stages who may be interested in tendering, it's communicating that complexity to them, and making sure that their scaffold designer is suitably experienced. Ask for previous project examples where they may have done something complex, that they can demonstrate to you that they've got the skills and experience to take the job on.  

Kim: As the cost of scaffolding can be a large part of project cost for repairs, would you say there's ever an argument for allowing drilled fixings to avoid a design scaffold cost? So, more of the budget can be spent on the repair scope?  

Bridget: This is the balance every project has to make, if that makes sense. As Alex said at the beginning, it's all about communication and engaging with the parties to work out the best solution for your building with the money available.  

Kim: We had a question earlier on about water kentledge leaking. I know water kentledge is quite a common method of resisting uplift in a scaffold. I don't know whether that's anything either of you have come across. Personally, I have no personal experience with that.  

Alex: Not of it leaking. I think there have been sites where unauthorised access has been made and they've been discharged, you know, because someone thought it was funny. But if you've got something, if you've got a leaking kentledge, then that would probably count  as a defect and  should be picked up during the inspection and rectified.  

Kim: Right. Are there any considerations specific to system scaffolding as opposed to traditional tube and clip scaffolding?  

Bridget: I think that system scaffolding, in my experience, is becoming more prevalent as it has great benefits in terms of speed of erection and everything. I mean, the same issues as we've talked about, it's all to do with the interfaces. And normally the interfaces, even on a system scaffold, are kind of... Actually, I forget what the other form of scaffold is, but  they're an add-on to the system rather than part of it. So, there's flexibility for installation.  

Kim: And a couple of questions about using or linking to existing lightning protection systems.  

Bridget: There's guidance on our website for lightning protection. And there is some specific, but it's not within our area of expertise, included within the scaffold guidance documentation.  

Alex: Yeah. I think the general is that if it's lightning protection, you can utilise the- if there is a system on the building, you can link into that. But that's not the same as earthing for risks. If you've got, say, electrical equipment being used on the scaffold, I think that's when the guidance mentions having a separate system for that. So, the lightning and the electrical thing are slightly different. But yeah, like Bridget said, there is guidance elsewhere.  

Kim: Thanks both. We've reached the end of the questions that we've received in the webinar chat. So, just to say thank you again, and to say have a nice afternoon to our audience.