Deck waterproofing structural considerations
The nature of the structure and associated dimensional stability, influences the choices in respect of the deck 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.
Stability
What scope is there for the deck structure to move? Understanding dimensional stability is key.
Falls
Decks must include falls which encourage rainwater to flow to outlets, rather than standing and pressuring.
Repairability
Modern design guiance for this type of waterproofing includes a focus upon the consideration of repairbility.
Bonded versus decoupled deck waterproofing
Best practice design guides indicate that bonded (adhered down) waterproofing materials are the ideal for podium decks and certainly buried roofs (arguably the latter is less accessible once buried).
Where a waterproofing 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.
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Falls and drainage are important aspects of deck waterproofing
Decks will always receive rainfall and management of that water is a key consideration. What you do not want is for water to collect, stand and pressure - it is hydrostatic pressure which forces water through any defects/pathways present, and long term standing water can be detrimental to some materials.
What we've seen in the past is no falls, and no drainage, or that the drainage outlets are installed at the level of the finishes (such as paving), and are too high to receive water at the level of the waterproofing. This is how you create a reservoir above the waterproofing, not what we want.
Decks should achieve falls of 1:80 in their permanent loaded condition to outlets which can receive water draining off of the waterproofing.
We could not have successfully completed this project without a flexible and proactive contractor, able to continuously deliver results under pressure in what were often difficult working conditions. When issues arose Trace assisted wherever they could, including where those issues did not fall directly within their remit. I would have no hesitation in recommending Trace to prospective clients”
‘Trace completed all of the works identified in the main building to a very high standard’. ‘All of the lads on site have been excellent and it has been a pleasure to work with you all.’
"Thank you so much for your generous and expert advice on how to cost effectively resolve the damp challenges at 422. Your guidance to our team has been great and given them the information and direction they need to get on with the job. Also thank you for linking us to your materials supplier so they can be sourced economically". *charity work*
"I think this is the best CDM installation I have ever seen. I have seen a lot. Everything about it is textbook. It is neat, tidy, straight, square…. Just perfect and the care and attention taken to fix the plugs to the exact centres ready for further trades is nothing less than a work of art. In addition to this, the site management is top-notch also. Everything about the project gives massive credit to Trace and all who worked on this project".
Quality assurance methods for deck waterproofing materials
Trace employ forms of deck 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 systems for decks
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 become the norm, particularly where decoupled waterproofing systems are employed.
Image courtesy of Vector Leak Consultants
Award winning experts in dealing with problems of moisture in buildings. Est 1974.
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