INTERFACES WITH STRUCTURE AND FABRIC

The way in which BS interface with fabric and structure are treated as, major, minor, modular—at walls, floors and ceilings, and finally specials. Only through knowledge of where and how BS relate to the building structure and fabric when finally installed can we properly plan for completion in the shortest possible time. It is the lack of appreciation of services interfaces and an inability to integrate their construction activity with those of the building works that can lead to an unforeseen hiatus, e.g. services works stop for fire spray on steelwork, or an area has to be vacated while the plant rooms are screeded. Situations such as these lead to claims, particularly on jobs where the programme shows M & E work as continuous. A little diligence in understanding BS interfaces prior to drawing up programmes can reap large benefits in productivity and site harmony.

Major interfaces for planning consideration are those where relatively minor value services work must be carried out in tight sequence with building work if delay to the latter is to be avoided;

examples are enabling works such as the building in of puddle flanges, the provision of flue templates for casting bolts in bases, providing and/

or fixing lightning protection connectors, tapes and earth rod pits.

The laying of underslab drainage in close coordination with the pouring of concrete bays is an example of a major interface occurring over a large area. Moving up the building, air intakes and discharges through the envelope and the building of riser shafts must be carefully considered so that building and services work can proceed with mutual efficiency. Externally the construction of ducts and trenches can play havoc with landscaping if not properly sequenced; see Table 5.8.

Table 5.8 Major interfaces (controlling activities) for building and services work

Minor interfaces need to be carefully searched out. If not given the right attention they can become a big problem. Particularly look for those situations where there are a number of repeated instances, e.g. location of socket outlets and switch plates in dry lined partitions. Taking this example further, electrical power run in conduit on the face of a blockwork wall studded out and plaster boarded may leave conduit (fixed to the blockwork) too far away from the socket outlet plate on the plasterboard surface. Who is to blame, the electrical design or the installing contractor? One will say ‘Your working drawings should have picked up the difference between stud and conduit box depths’, the other replying,

‘You should have produced a co-ordination detail’. Followed by ‘We weren’t paid to do co-ordination.’ Meanwhile the builder, although not looking at costs attributable to him (unless the stud depth was wrong?) is frustrated by the loss of progress that the rework will cause. In similar vein, look carefully for any specified requirement of services terminals needing to be coordinated with joint lines in tiled areas. This train of thought takes us into another specific area, of providing better facilities within buildings for disabled persons. The BS facilities disabled people need to use for access into and movement through buildings, and in toilet areas, are usually precisely dimensioned. If they are not, instructions should be sought from the DT.

Walls, floors and ceilings take us from the minor interfaces largely dictated by occupant usage of the services, into those related to structure and fabric module dimensions. Here we have seemingly impossible compatibility, at best limited rationalization. Consider Fig.

5.4(a) integrated with (b) Services Outlet Modules. The architect and structural engineer have little difficulty on reaching agreement on a structural grid of say 6 m to 9 m that will allow the architect to express his thoughts and achieve coherence and beauty in the external elevations. Within the structural grid further modular divisions of 1500 mm, 1200 mm or 1800 mm go naturally into smaller subdivisions of 500 mm or 600 mm. The architect has found reasonable freedom for the choice of wall, floor and ceiling elements. Very importantly the letting agent and client have their flexibility criteria for creating an acceptable variety of cellular offices. These too can be accommodated. Enter the villain. To create a suitable mechanically ventilated or air conditioned and artificially lit environment of optimum design the BS designer would wish to locate the outlets for those services in positions that rarely coincide with the architect’s design model. The situation is made worse the greater the number of alternative internal partition layouts that the services designer has to cater for. Before we can make this better it may get worse. Legislation and/or the insurers may demand sprinkler protection. Much has, and can be done by the BS industry to accommodate modular layouts, but with the penalty of increased cost.

The sprinkler design engineer cannot be so accommodating. To provide

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138 Planning and programming

coverage according to the hazard rating for the risk category, partition layout changes can mean more heads in different positions. There is just about enough tolerance in sprinkler design for a head to be positioned in the centre of a 600 mm×600 mm ceiling tile. To centre an outlet in a 1200 mm×1200 mm tile may mean that in order to avoid being ‘out of distance’ it has to be offset to a degree that it will not provide adequate coverage to the area it is protecting. Change sprinklers for heat or smoke detectors and the situation is similar. Passive detection and protection systems take priority in the discharge of their function over accommodating building modularity.

Due to its brittleness the building module is king:

• It limits options.

• It requires rigid coordination.

• It supports abuse through bad management/coordination.

• It repays careful study in programming construction.

Figure 5.4 (a) Typical office planning modules; (b) typical office services outlet modules.

Special interfaces are the wild cards of which security systems are a good example. Look at Table 5.9. Not all, of course, are provided in every building. The pattern of provision through the building may sometimes be detected from studying the drawings and specification, e.g.

for card access along circulation routes into different departments.

Generally, though, it is security services relationship to the geography of the site and the building layout that must be studied in this example of special interfaces. The door phone that is provided at entry to a block of social housing accommodation may be the one piece of ‘high tech’ in what is otherwise domestic-scale building services. Tremblers embedded in the external walls will need to find a route for the terminal wiring. The location of CCTV cameras may require a dedicated duct or trench for wiring through the hard or soft landscaped areas. Similar interfaces occur with external lighting where boundaries between what is particular for security or safety can become blurred. Taking both together they fall naturally into two groups. Lighting mounted off the building creates interfaces in its BWIC and access for fixing the terminals which may need to be brought forward for installation before scaffolding is struck. If not considered in depth, one can be involved in the expense of mobile access towers or waiting until the facade maintenance equipment is operational on very tall buildings. The second group are those positioned externally along the site’s traffic and pedestrian routes, for car parks and flood lighting. It is a pity not only for the time and cost lost, but for the visually unattractive, albeit temporarily until weathered, look of remedial work to hard and soft landscaping.