The nature of the structure and associated dimensional stability, influences the choices in respect of the waterproofing materials which can be employed. In new construction there may be opportunity to influence what structure is proposed, whereas for existing structures, what is present may dictate the approach which has to be taken.
In either case Trace are experienced both in the design and installation of both podium deck and buried roof waterproofing systems. Photo above is 1200m2 buried roof / podium deck above a car park in central Manchester, with deck waterproofing designed and implemented by Trace, this including a 'blue roof' area.
What scope is there for the deck structure to move? Understanding dimensional stability is key.
Decks must include falls which encourage rainwater to flow to outlets, rather than standing and pressuring.
Modern design guiance for this type of waterproofing includes a focus upon the consideration of repairbility.
Best practice design guides indicate that bonded (stuck down) waterproofing materials are the ideal for podium decks and certainly buried roofs (arguably the latter is less accessible once buried).
Where a material is 'fully bonded', any water bypassing the membrane should not be able to track laterally between the membrane and the structure, so if the structure itself is impermeable (appropriate concrete), this can provide enhanced protection against leakage.
Where structures are prone to movement - certain types of deck structure are, or you cannot gain certainty regarding the extent of likely movement (existing structures), and with careful consideration, decoupled systems can be employed which design out the movement consideration.
Trace employ forms of waterproofing which can be tested via what is know as spark or holiday testing. An electrical current is passed over the membrane via specialist equipment which identifies if there is any loss or conduction of the current through the waterproof material, i.e. is there a hole or thin section weak point, representing a risk to the system. This is undertaken by a third party and is an important measure in ensuring the quality of the installed waterproofing system.
Permanent leak detection
These are systems which are installed in association with the waterproofing system, with the principle being that in the event of any issue, it is possible to locate the area in which water is bypassing a membrane. Deck structures inevitably include multiple layers of material (for example - insulation), through which water can track laterally meaning that where you see water internally, may not match the location of a defect in the waterproofing. Such systems are in their infancy in the UK waterproofing market, and the focus is always on design, installation, materials and QA, such that defects are avoided.
Nevertheless, it is the norm in basement waterproofing for Designers to consider risk of defects and strategy for repair, (both key points in BS8102 Protection of below ground structures against water) and we note that some of latest design guides produced (we have been involved in editing the PCA guidance doc. ourselves) advise the same requirements in respect of repairability. Further to this we expect that these systems will bevome the norm, particularly where decoupled waterproofing systems are employed.
Image courtesy of Vector Leak Consultants