Problems That Dry Lining Companies Frequently Encounter Construction Essay

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When the air barrier consists of plasterboard dry lining, dry lining companies have to omit the 'out of sight, out of mind' approach that may have been implemented prior to the amended Building Regulation of Part L. Any defects in the construction of a liner wall subsequently show up in the pressure test. An air leakage audit is then required to identify the air leakage paths if the building fails the specified airtightness requirement. (www.mcconsultingengineers.ie)

Generally the problem experienced by dry lining contractors is the interface junctions between two different elements, e.g. where the dry liner wall meets a column or a concrete wall. Problems may arise due to insufficient detailing, incompatibility of materials, lack of co-ordination between trades, etc. (www.bath.ac.uk)

Remedial works to the air barrier may be very expensive, disruptive and prolonged for the dry lining contractor. Remedial sealing is therefore extremely problematic for the contractor. A way in which to enhance the air barrier is to ensure that subsequent trades do not compromise the air barrier. The air barrier may be compromised by another contractor accidentally damaging it or deliberately penetrating it in order to complete their work to programme of works. It is vital that the damage caused to the barrier be repaired immediately. (www.mcconsultingengineers.ie)

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Voids created in the walls for air ducts or piped services significantly reduce the probability of the room achieving its required airtight specification. A room with several penetrations is less likely to achieve a greater airtight value than a room with fewer penetrations, since service penetrations in and out of a building contribute as a major source of air leaks. (www.seda2.org)

It is common for design drawings for dry lining contractors to contain little or no information on the location of the primary air barrier or airtightness issues. This ultimately results in those involved in constructing the air barrier for the building not being aware of the location, its purpose, the importance of maintaining continuity of the air barrier, nor areas of the construction where particular attention to detail is required to ensure airtightness. (www.leedsmet.ac.uk)

A problem experienced by dry lining contractors is that the designers do not specify exactly where the airtight layer is on the drawing. The designer does not identify the airtight envelope on drawings for the contractor. Consequently on site the airtight envelope is not labelled, therefore other contractors are not aware of its location. The lack of awareness amoung contractors and designers is detrimental, e.g. if an operative needs to drill a hole through a dry liner wall or ceiling to thread pipes or cables through they are not aware that the penetration must be resealed afterwards. It is important that such penetrations are managed in a more controlled manner than they currently are from the dry lining contractor's perspective. (www.bath.ac.uk)

If joints are unavoidable then design-in a seal. This may be difficult for dry lining contractors as the method chosen to seal joints depends on the size of the gap between components, the amount of likely movement, the practicalities of application and the need for weather / air tightness. (www.mcconsultingengineers.ie)

All buildings move to a greater or lesser extent depending on its use and this movement has to be accommodated in the design from the outset. This is troublesome for contractors as movement or expansion joints will need to address airtightness as well as movement. Not all joints do so, so careful deliberation is required during the design stage. (www.mcconsultingengineers.ie)

Dry lining contractors are faced with a multiple of complex details for the external airtight envelope. Complex solutions to airtightness are likely to be more prone to poor execution and potentially to greater vulnerability to differential movement, failure of sealants, and dislocation of components etc. (www.environ.ie) (www.seda2.org)

Due to a lack of information on the commercial sector, the author had to resort to the residential sector, as the basics are similar. ''One of the main air leakage paths within the UK dwellings is plasterboard dry lining (Stephen, 1998 & 2000). Problems arise with plasterboard dry lining when air can freely move into the gap between the plasterboard and the masonry wall, especially where plasterboard is fixed to the wall using adhesive dabs. The air gap between the plasterboard sheet and the masonry wall then act as a plenum, effectively interconnecting all of the leakage paths within the dwelling.'' (Johnston, Shenton, Bell, Wingfield, 2004:17)

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Figure 1 Discontinuous ribbons of adhesive used to seal plasterboard dry lining.

(Johnston, Shenton, Bell, Wingfield, 2004:17)

''Service penetrations are known to be a significant route for air leakage (see Stephen 1998 & 2000). The report on Robust Construction Details (DEFRA, 2001) states that particular care on site should be paid to service penetrations and all service penetrations should be sealed with expanding foam or other suitable sealant, whether in the wall [Dry liner wall], ground floor, intermediate floor or ceiling… Observations from site illustrate that little attempt has been made to seal the majority of service penetrations through walls, ground floors, intermediate floors and ceilings, and where attempts at sealing have been made, the penetrations are generally inadequately sealed and inappropriate sealants have been used to seal gaps around the service penetrations.'' (Johnston, Shenton, Bell, Wingfield, 2004:19)

Figure 2 Diagram illustrating sealing of service penetrations [Source: DEFRA, 2001]

Site Supervision and Workmanship

A major factor that influences air leakage is the level and quality of site supervision and workmanship during the construction of a building. Similar types of buildings with similar details may have very different air leakage rates. As a result workmanship is often citied as the primary reason why airtightness standards are not achieved in the construction sector. (www.leedsmet.ac.uk)

From the authors personal experience during industrial placement all aspects of dry lining work needs to be inspected as work proceeds. It is extremely complex to inspect the airtight barrier on the building once work is complete on site, as it is generally covered by internal fixtures and finishes. Great awareness and concentration is required on inspection, to ensure that the air barrier is not defective in any way, paying particular care to parts that will be hidden on completion. (www.mcconsultingengineers.ie)

Once awarded the contract and the air barrier consists of plasterboard dry lining, it is the dry lining contractors responsibility that the airtight barrier is achieved. A problem faced by contractors is that the employees are not aware as to their contribution and responsibilities for the overall airtightness. (www.seda2.org)

Consequently the issue of 'good or bad' workmanship in general is a key factor with air tightness. This is what makes the supervision and inspection for the dry lining contractor's more difficult to control. (www.seda2.org)

Due to a lack of information in the commercial sector regarding dry lining contractor's site supervision and workmanship, the author resorted to the residential sector, as the fundamentals are similar. Stamford Brook is a development of around 700 cavity masonry dwellings being constructed on part of the National Trust's Dunham Massey Estate near Altrincham in Cheshire. At Stamford Brook an example of a perceived workmanship problem was the maintenance of a continuous ribbon of plaster adhesive around the perimeter of the plasterboard dry lining. It was observed that with very careful attention to detail and enough time allocated, a significant reduction in the level of air leakage was attained using plasterboard on dabs. (Miles-Shenton, Wingfield & Bell) (www.leedsmet.ac.uk)

Another conclusion from Stamford Brook was that it was impossible to divorce workmanship, not only from design but also from other issues of construction management such as training, communication and quality control. It was clear that many operatives were eager to carry out a high-quality job but that, as far as airtightness was concerned, it was complicated for them to be clear about what they had to do or who was responsible for achieving an airtight envelope. (www.leedsmet.ac.uk)

Quality on site

It is of paramount importance that all parties involved on the project from client, contractor and consultants to all site staff and operatives and off site suppliers understand the concepts of air tightness and how they are involved in playing a vital role to that aspect of construction. It only takes a minute section of the dry lining wall of the building to be permeable to ensure a failure to comply. This ultimately results in the remedial works which are costly for the contractor not to mention the impact it may have on the building programme as a whole with time delays. Therefore it is essential that an endeavour is put into practice to educate the staff and that all the staff works a team. Issues of thermal bridging, continuity of insulation and the correct construction of designed details need to be addressed to ensure that airtightness is achieved. (www.hrsservices.co.uk)

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Although airtightness testing is carried out a few weeks prior to practical completion of a project, it is vital that the dry lining contractor has a quality system in place so that remedial works are not necessary. Dry lining contractors should also try to obtain the airtightness test at a time where the barrier is complete and when remedial works are relatively simple to perform. The airtight test generally consists of two tests, once when the air barrier is complete and one prior to the handover stage. (www.seda2.org)

Airtightness testing is generally carried out a few weeks prior to practical completion of a project. The airtight test generally consists of two tests, one when the air barrier is complete and the other prior to the handover stage. It is best practice that the dry lining contractors strive to achieve the required air permeability rate first time round. They then can improve that rate by addressing issues in the audit that is likely to accompany it. Dry lining contractors should also try to obtain the airtightness test at a time where the barrier is complete and when remedial works are relatively simple to perform. If for instance the air barrier is not complete but the main contractor is adamant of having an air leakage test. The incomplete barrier would have to be temporary sealed with an impermeable material; this is a timely and complex procedure. The result of the test may also prove to be an unfair reflection of the dry lining contractors work to date and the location of the leaks may be more difficult to locate. (www.hrsservices.co.uk)

Quality Policies

Dry lining contractors have not implement an enhanced strategic quality policy in order to succeed in maintaining airtight construction. Quality of workmanship and adequate construction of details are the main issues affecting companies to date. With the stringent Building Regulation in place, increased emphasis on quality policies have to be adhered to. (www.leedsmet.ac.uk)

High-quality workmanship is obviously significant, but workmanship unfortunately always appears to be of poor quality due to the context in which the staff has to work. Stamford Brook studies have shown that Buildability of designs, lack of detailed design, lack of specific training and the lack of a general quality control procedure underlies many workmanship problems. If careful attention to detail and adequate time allocated, the method of airtight construction can increase dramatically. (www.leedsmet.ac.uk)

Some issues that the quality policy may incorporate to enhance it are an improved management strategy, communication and quality control. Operatives are generally eager to construct to the required specification of detail but 'short cuts' are taken in-order to complete the task in the required time. Operatives are not aware that they are responsible for the achieving the airtight envelope, and that the common trend of the past of 'cutting corners' is not acceptable in the current practice of the industry. (www.leedsmet.ac.uk)

Management

On - going review of the design is very important. The project management do not ensure that details of all design changes involving elements of the external envelope are distributed throughout the design, procurement and construction teams. This may have consequently effects for dry lining companies. (www.environ.ie)

Not all project programmes reflects dry lining contractors required sequence for effective formation of the air barrier and insulation installation. Some trades are not permitted access to form not only the part of the insulation layer or air barrier for which they are responsible, but also to ensure that continuity is achieved between their works and that of other contractors. (www.environ.ie)

An ''Air Tight'' milestone is not always included when compiling the programme. This puts immense pressure on dry lining contractors if the air barrier is fails the air tightness test. Ignorance of this date prevents management to schedule thorough envelope pre-test inspections and test dates in advance of the final product. (www.environ.ie)

Once the air barrier consists of plasterboard dry lining, it is the dry lining contractor's principal liability to deliver the air tightness performance overall and the most likely task on any but the smallest jobs will be the co-ordination between management. The contractor must be clear that he carries responsibility for the overall air tightness and in turn must ensure that all personnel and operatives are clear about the extent of their responsibilities. Experience suggests that the best performance has been achieved by contractors who employ a dedicated individual / team to carry responsibility for air tightness, to inspect the works and instruct as required. (www.seda2.org)

The issues of air tightness are closely linked to issues of good or bad workmanship in general for contractors. This can make the issue more sensitive and more difficult to control. Even simple buildings are immensely complex and so the most important aspect of all is the creation of an overall culture of careful, tidy, accurate and airtight construction, something which can not be simply forced through a performance specification. (www.seda2.org)

Communication

Every year defects in the UK construction industry cost at least £1 billion to rebuild or repair. A number of the defects are the result of poor communication, for example, an inadequately detailed drawing, operatives being given the incorrect instructions or technical information not being available. Improvement in communication should result in an increase in the quality of the build and a reduction in the level of defect occurrence. (projects.bre.co.uk)

Studies at Stamford Brook have emphasised the critical nature of communication and the potential impact it may have on airtight construction. It is vital that there is an improvement in flows of information both upwards and downwards in the formal management structure in company's, an example of this may be operatives reporting an incorrect drawing to the site office and the site office will contact the main contractor's office, where the incorrect detail can be rectified. (www.leedsmet.ac.uk)

Frequently at Stamford Brook and many other sites observed throughout the UK, design information was not available, not at a sufficient level of detail, confusing, complex or just not referred to by operatives. This lack of information tended to lead to a rather diffused process as operatives followed their instinct rather than using detailed design information, which ironically was not present.

(www.leedsmet.ac.uk)

Also there did not appear to be any particular well developed mechanism for feed back of information on air tightness performance and specification. It was not clear how the design and construction lessons were being absorbed for use in making vital improvements to processes or actual designs. This can be linked with the necessity for a clearly defined quality control process, for without such a process there can be no definition of problems, identification of their causes or framing of solutions. (www.leedsmet.ac.uk)

Majority of personnel and operatives involved in the procurement and construction of the building fabric are not aware nor understand the necessity for insulation continuity and airtightness. The lack of awareness associated with these issues, results in components being engineered out of the design for cost savings. (www.environ.ie)

Awareness is not raised at key stages during a project, for example, briefing procurement offices and site tool-box talks. As a result parties can not clearly identify where and how insulation continuity and the air barrier are to be maintained. Operatives directly involved in constructing the insulation and air barrier do not draw attention to difficulties experienced on site or request direction. This lack of communication is likely to have detrimental effects on construction. (www.environ.ie)

Operatives not directly involved in the building fabric are not entirely aware of the importance of insulation continuity, the air barrier and the flagging up of any breaches through these "lines of defence". They do not remedy potential thermal bridges or air leakage routes brought about by their own activities, or to seek help from other trades, depending on the nature of the breach. (www.environ.ie)

Quality Control

''Quality control is critically important to a successful construction project and should be adhered to throughout a project from conception and design to construction and installation. Inspection during construction will prevent costly repairs after the project is completed... For construction projects, quality control means making sure things are done according to plans, specifications and permit requirements'' (Satterfield, 2005:1)

Many dry lining contractors have no system in place for monitoring the quality of their processes and products. Experience illustrates those contractors without Quality Assurance (QA) hinders them to check for insulation continuity and air tightness. An effective QA control is that insulation continuity and air tightness are considered during all design changes and material substitutions affecting the external envelope. An ill-formed design change may jeopardise the final performance of the building envelope. The lack of a QA process in a company indicates that they do not inspect finished works especially the building envelope. This in turn prevents management to inspect that all works are properly constructed prior to being covered over. (www.environ.ie)

Construction quality can have a significant impact on air tightness. An overwhelming conclusion from the Stamford Brook Field Trial and from general observation of the UK house building industry as a whole is that quality control processes are extremely diffuse with a number of actors playing similar but different roles which are almost always carried out in isolation. It is perhaps not surprising that with no clear air tightness quality control process in place, sequencing is often out of the phase and known errors tend to be repeated time and time again. (www.leedsmet.ac.uk)

Another quality control issue observed at Stamford Brook that can lead to air tightness concern for contractors is the different tolerances that were constructed to by different trades. Items and components that are manufactured off site to high tolerances are often fitted into structures built by trades that are not operating to the same degree of precision. As a result, performance and workmanship issues can occur when construction is outside these tolerances. (www.leedsmet.ac.uk)

Quality control is not a primary objective for all the members of a dry lining company. Managers do not take responsibility for maintaining and improving quality control. Employee participation in quality control is not sought after nor rewarded, for example the introduction of new ideas. Consequently, quality improvement is not served as a catalyst for improved productivity. (pmbook.ce.cmu.edu/13)