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Car Park Deck Waterproofing Systems

Multi-storey car parks are an integral part of modern city life and the car park owners and operators increasingly realise that they must be clean, safe and welcoming in order to attract and retain our custom wherever we have a choice of where to park. A key part of this is to prevent water ingress through the decks leading to unsightly damp and cracked, spalling concrete, slippery floors and damaging alkaline salts dripping onto the car paintwork and all leading to expensive claims.

So actually, everybody has an interest in preventing water and de-icing salt penetration in or through car park decks – Car Park Owners, Operators, and the Users. The potential damage and deterioration that water and water borne salt ingress can cause for the car park structure, the dangerous conditions created for pedestrians and the damage caused to car paintwork – all result in considerable additional costs and claims (then more costs) for the Owners and Operators. In addition all of this causes considerable inconvenience and time and effort for the users to handle these situations, process and mitigate their claims and recover from any injury as well.

As a consequence the importance of providing a reliable deck waterproofing and wearing surface on multi-storey car parks has also been recognised and greatly increased in importance over recent years. This is an area where NCC Resin Floor Site flooring specialists have particular expertise and experience.
Resin Floors for Car Park Deck Waterproofing

Car Park Deck Waterproofing Requirements:

The selection of the most appropriate deck waterproofing and wearing surface system is dependent on the existing condition of the structure and the decks, any previous surfacing treatments, their anticipated future level of use and exposure, plus the economic constraints and now increasingly there are now also demands for the sustainability of the deck waterproofing products.

NCC Resin Flooring Site experts and help you to make the right decisions in assessing your car park’s condition and deck waterproofing requirements, then in selecting, specifying and installing the most appropriate and cost effective resin based systems. This applies equally to new car parking structures and to the refurbishment and upgrading of existing car parks, including the different areas within them both, where special considerations and potentially different treatments may also be required i.e. on the ramps, the turning circles and on the externally exposed top decks.

Fast Setting Car Park Deck Waterproofing

The other key factor in deck waterproofing is always the time available to do all of the works required and get the cars parking on the finished surface once again. This obviously has financial and disruption implications and so must always be a major part of the car park deck waterproofing system selection process – For example is the time available to allow cementitious repairs or for new concrete to fully dry out – or indeed is there only the shortest window of opportunity meaning that a spray applied fast-curing Polyurea system (VIP Quickcoat) will be the only viable solution and other criteria must be accommodated to allow this systems rapid installation and return to service. Please refer to the Polyurea Resin Flooring Section of this website for more specific information on this approach.

If you would like help and assistance with your specific project requirements, please call any of our offices and one of our Resin Floor specialists will be pleased to assist you.

There are several important differences between the deck waterproofing requirements, the key system selection criteria and the application / installation of the right deck waterproofing and wearing surfaces for new and refurbishment multi-storey car park projects:

Deck Waterproofing on New Car Parking Structures

In a new multi-storey car parking structure the reinforced concrete decks will normally tend to be flat and level, recently laid to the correct falls, without any serious / extensive surface defects, damage, or contamination, and the movement joints are usually correctly located. Therefore the concrete deck surfaces can easily and economically be mechanically prepared as necessary, ready to accept the selected protective deck waterproofing and wearing surface system (vacuum blastcleaning is usually the best method of carrying this out). This surface preparation results in a sandpaper -like, uniform surface texture that is ideal to accept the deck waterproofing and wearing surface systems. The deck waterproofing systems for new car park decks are normally from 1 – 5mm thickness, according to the different decks and areas of the deck’s exposure levels and the owner’s requirements.

Deck Waterproofing on Existing Car Parking Structures

With existing car parking structures a professional Condition Survey must always be undertaken to determine the precise nature and extent of any damage or defects. Any structural damage or defects must be repaired and rectified / made good prior to the deck coating works, before they can be successfully undertaken and provide the owner with a durable and waterproof wearing surface.

Existing concrete car park decks are frequently contaminated and damaged, sometimes severely, plus the concrete surfaces will have been attacked and their profile increased and roughened by scaling due to freeze-thaw damage. This is accelerated by de-icing salts brought into the structure on vehicles, or used to maintain car and pedestrian safety during the winter on ramps, turning areas and stairways.

This means the concrete surfaces will generally need more aggressive preparation and cleaning prior to application of a new deck waterproofing system, than on new car park decks, in order to clean or remove the contaminated, damaged, or deteriorated concrete. Therefore this mechanical preparation (using vacuum blastcleaning techniques where possible due to its overall effectiveness and efficiency) will necessarily have to be harsher and more aggressive than would be required on new concrete surfaces. This will result in a greater profile depth and roughness, which in turn will need to be made good and levelled as an additional operation prior to, or as part of the new deck waterproofing and wearing surface system application.

As a minimum result, this additional surface profile will greatly increase the consumption of the priming and / or intermediate resin coats that are required to provide a uniform surface for application of the waterproofing / wearing layer, particularly if the deck waterproofing system has to be designed with crack-bridging properties to accommodate thermal movement i.e. for top decks exposed to direct sunlight and the different seasonal weather conditions.

It is also common in car park refurbishment and upgrading that the parking deck levels and falls to drainage outlets may also need to be made good and reinstated. Any cracks in the concrete surface must be sealed, or their movement accommodated with additional joints brought through the new deck waterproofing system, or these must be accommodated with a crack-bridging deck waterproofing system. Broken or damaged joint arrises will also frequently need repair and reforming. For detailed guidance on how to repair and make good all of these problems and damage, please visit our ‘Floor Repairs, Cracked Floor and Joint Arris Repairs’ page.

All of these different and very variable repair factors can have a considerable effect on the potential durability of the refurbished structure and in ensuring the intended long service life of the new deck waterproofing system. If the correct quality and quantity of these repairs are not correctly carried out then the new waterproofing system will not perform and the future integrity of the structure will be compromised. However as all of these different repair requirements and factors can obviously make a very significant difference in the cost of the car park refurbishment, at Resin Flooring Site we recommend a professional evaluation of the potential budgets and works required using ‘life-cycle costing’. This is in order to obtain a clear view of the requirements and to fully evaluate the different options and then specify and schedule the most appropriate refurbishment works accordingly.

Special Waterproofing and Flooring Areas on Car Park Decks:

There are some areas of all reinforced concrete decked car parks that always require ‘special consideration’ and then usually they should also receive additional or alternative treatments in both new construction and refurbishment works. These areas include:

• Car Park Ramp Waterproofing Systems:

The ramps for access in, up, around and out of a car park are potentially subject to increased mechanical abrasion and vibration from traffic; they are at least partially externally exposed to weathering and rainwater; they will collect de-icing salts from vehicles entering the car park – in addition to any salt used by the car park operator; plus they can have complex / substantial movement in joints connecting the ramp areas with rest of the support structure and the parking decks. Therefore ramp areas always demand special consideration and treatment with regard to ensuring durable watertightness. Generally this involves using higher deck waterproofing system thicknesses and / or increased levels or grades of the system performance specifications for the ramp areas.

During the application of flow applied resin deck waterproofing materials on a slope, this can be problematic due to the resin products that are used for the waterproofing system build-ups are designed with excellent ‘flow’ characteristics, which conversely are also an important advantage in their application on ‘flat’ areas such as the parking decks themselves. Therefore it is also important to select and specify a ramp surface waterproofing system with a sufficiently thixotropic nature, for slump-free application when applied and broadcast with aggregates to build up the system thickness on the slope of the ramps on each project. The ramp waterproofing system must also still maintain its required level of abrasion resistance and the necessary crack-bridging properties.

NCC Resin Flooring Site specialists can advise you on all aspects of the selection and installation of the waterproofing system on the ramps and in all of these areas that require special consideration.

• Deck Waterproofing for Turning Circle Areas

The reasons for special consideration of the Turning Circles on a car park deck can be similar to those of the car park ramps apart from the slope. Dependant on the design of the car park and the size (radius) of the turning circles, these areas may well also be subject to increased dynamic load and mechanical stress, which will require additional deck waterproofing and protection – From experience at NCC Resin Flooring Site we normally find that this level of loading will usually be somewhere between the performance required for the systems that are appropriate for the parking decks and the performance that is required for the ramps.

This additional deck waterproofing system performance requirement must therefore be clearly defined and then detailed in the specifications for the overall deck waterproofing works.

• Waterproofing Externally Exposed Car Park Decks

It is clear that externally exposed decks will have the highest external weathering exposure to the elements and therefore are likely to be subject to the highest levels of thermal movement, thermal shock and UV light radiation. Therefore the anticipated effects of this exposure on the structure, the decks and the potential deck waterproofing system must be fully considered and evaluated. Then the appropriate performance requirements can be defined and the right deck waterproofing system selected, specified and detailed for the exposed and partially exposed parking decks.

• Waterproofing Below Ground Car Park Decks

Below ground parking decks and to a lesser degree, parking decks at ground level without lower parking-levels, can all be subject to water or water vapour penetration from below. This is a, particularly risk if there is inadequate or damaged waterproofing membranes and drainage systems in and below these parking decks on the structure.

As a result NCC Resin Flooring Site experts highly recommend that all below ground car parking areas should have an emergency automatic pumped drainage system installed at their lowest point (sump and pump approach) and that either:

- A vapour permeable deck waterproofing and wearing surface system should be selected.


- A suitable moisture barrier must be applied to the prepared concrete surface first, in order to allow a vapour-tight deck waterproofing and wearing surface system to be installed, which would otherwise not allow any trapped water and water vapour to escape by diffusion through the system, without risk of osmotic blistering and bubbling or delamination from the concrete deck surface.

• Waterproofing Parking Decks Over Residential and Commercial Premises

When car parking decks are directly above residential or commercial premises there are several additional criteria, such as incorporating thermal insulation above, within or below the concrete slabs to consider. There is also normally no chance of easy future access to the deck soffit for any routine or regular inspection and maintenance, so any future water ingress would undoubtedly cause severe disruption and no doubt also be extremely expensive to repair.

Therefore in these situations it is always prudent to ‘err on the side of caution’ and always ensure that an extremely high performance, tough and abrasion resistant, crack-bridging and durable deck waterproofing and wearing system is used. This may mean that in these areas the deck waterproofing system should possibly even be deliberately over-designed, even for those parking decks areas which will otherwise be non-exposed or intermediate decks in the structure. This is because the potential as the disruption and costs of any rectification of leaks and the consequential damages can be very punitive to everybody involved.

If you would like help and assistance with your specific parking deck waterproofing project, then please call any of our offices and one of our Resin Floor specialists will be pleased to assist you.

Criteria for the Deck Waterproofing System Selection:

The following may not be exhaustive or necessary for a specific structure, but this summary is intended as a Guide to the main requirements, conditions and exposure criteria that should be considered when defining the most important criteria and the performance required before being able to select the right deck waterproofing systems for your parking deck waterproofing project:

• Structural / Non-Structural Cracks in the Concrete Parking Decks: Are there any cracks in the concrete deck? – Are they in the top surface of the deck and if access is possible, are they also visible in the bottom of the deck slabs on the soffits i.e. do the cracks go right through the deck? Are the cracks of structural significance and what has originally caused them? Are the cracks still moving due to traffic vibration or other stress and loading for example? If so by how much are they moving and do these cracks in the reinforced concrete slabs have any structural significance?

- Important: For any crack or situation with structural significance then a suitably qualified and experienced Structural Engineer must be consulted for advice.(Please also refer to the 'Thermal Movement in Parking Decks’ section below)

• Joints in the Structural Concrete Parking Decks: Is there adequate joint movement capability in the Movement Joints in the deck to accommodate the anticipated levels of thermal movement, dynamic loading and any other anticipated movement of the deck? How have the other joints (i.e. Daywork joints / Construction joints / Isolation joints) in the reinforced concrete parking decks been formed and previously treated? Are these all securely and safely sealed for the future, or is additional joint pre-treatment and sealing required?

- Wherever there is any concern over the capability or capacity of movement joints to accommodate the anticipate movement then a suitably qualified and experienced Structural Engineer must be consulted for advice and refer to the Emseal NCC Joint Sealing approach on the ‘Joint Systems’ Page of this website.

• Drainage in and Around the Concrete Parking Decks: Is there adequate provision for rainwater collection, drainage and removal from the structure? How have the drainage details been incorporated in to the deck and sealed at their junction with any existing or proposed deck waterproofing membrane? Is there evidence of past or current ‘ponding’ of standing water on the deck surface? i.e. Are there adequate falls for the required drainage requirements, or must additional work be carried out to create or reinstate these falls? This type of work will normally need to be carried out with suitable cement or epoxy resin based screed for example?

• Deck Waterproofing System: Vapour Permeability Requirements: Is the reinforced concrete parking deck below ground level or at ground level? If so is there a secure and intact damp-proof membrane (DPM) installed between the concrete structure and the ground? ? Are any drainage or water pipes and channels in or below the deck? Does water vapour need to be able to escape through the new deck waterproofing system? If so then any proposed new deck waterproofing and wearing system must be waterproof, but water vapour permeable, in order to allow the water vapour to diffuse through the system and escape.

• Parking Deck Concrete Surface Profile: What is the surface profile of the existing concrete, or the new concrete surface? If yet to be placed, then what is the specified concrete surface finish and profile, plus how is this going to be achieved?

Is this concrete surface and its profile suitable to accept the new resin waterproofing and wearing surface system, or does it need any additional surface preparation to achieve the open textured, sand-paper like concrete profile that is normally required for the application of resin based waterproofing materials? If so then vacuum blast cleaning is usually the best method of carrying this out on new and existing parking decks.

On existing parking decks, vehicular traffic causes mechanical wear and abrasion of the surface which means that the surface preparation will need to be harsher and more aggressive, leading to increased consumption of the waterproofing system priming and levelling coat materials.

For more information and guidance on the concrete profile requirements and how to achieve this, please also refer to the ‘Deck Waterproofing on New Car Parking Structures’ and ‘Deck Waterproofing on Existing Car Parking Structures’ subpage sections above, together with the ‘Surface Preparation for Resin Flooring’ pages of this website.

• Deck Contamination: Has there been any liquid chemical exposure or other spillages on the decks that could affect the adhesion or performance of the new resin waterproofing and wearing surface system. i.e. automotive fluids including fuel – petrol and diesel, engine oil, grease, brake fluid etc., or chlorides from de-icing salts, etc.? As a result, is any additional surface pre-cleaning required prior to the mechanical surface preparation of the concrete? This is always necessary on existing car park decks that are to receive new resin based deck waterproofing system. Please also refer to the ‘Deck Waterproofing on New Car Parking Structures’ and ‘Deck Waterproofing on Existing Car Parking Structures’ subpage sections above, together with the ‘Surface Preparation for Resin Flooring’ pages of this website

• Concrete Deck Moisture Content: In both new and existing concrete decks the moisture content must be at an acceptable level, which is generally defined as not more than 4% parts by weight (pbw), before a new resin surfacing system can be applied. This could be from residual water after hydration in the concrete, water ingress from the ground or water penetration after rainfall; whatever the source, the water must be allowed to evaporate and the concrete must dry out before the deck coating system is applied. Alternatively an effective moisture barrier, or a surfacing system that is vapour permeable, should be used to allow the moisture to evaporate over time as water vapour.

• Future Use – Traffic Type and Level: What is the intended future type, activity and level of traffic in each area and also within each deck of the car park? This can effectively be evaluated and summarised for different areas as follows in order to relate this to developing the necessary deck waterproofing system performance requirements:

Pedestrian only = Low
Main Aisles and Car Parking Bays = Medium
Ramps and Turning Circles = High
Delivery Vehicle Parking / Turning and Unloading Areas = Very High

The deck waterproofing and wearing surface system selected must have a skid resistance and abrasion resistance that is suitable for the exposure in each of these different areas and that is suitable for maintaining this performance in both wet and dry conditions – according to the anticipated exposure in each are of each deck.

• Future Thermal Exposure – i.e. External or Internally Exposed: Externally exposed parking decks are subject to much greater thermal movement possibilities due to their wider surface temperature exposure range; from -15 to +40°C is now not uncommon over a full year throughout much of the UK. This degree of thermal expansion and therefore thermal movement in the parking decks, means that many exposed deck surfacing systems must be designed to be not just flexible, but also sufficiently elastic and crack-bridging to accommodate the Structural Engineers anticipated levels of this movement in the parking deck surfaces. The use of light coloured deck waterproofing externally can also help to considerably reduce the ‘heat island effect’ and reduce the higher limits of temperatures attained in the summer months – Always provided they can be kept clean and do not discolour in UV light.

• Future Chemical Exposure (Water & De-icing salts, Auto fluids etc.): Will the parking deck be subject to direct water and de-icing salt exposure and therefore the potential for freeze-thaw damage and if so to what degree? Whenever cars and other motor vehicles are parked for long periods there is the possibility for leaks and spillages of their different automotive fluids including fuel – petrol and diesel, engine oils, coolant and screen wash, etc., plus what is probably the most aggressive chemicals to synthetic resins and coatings – hydraulic oils such as brake fluid. What level of resistance to these automotive fluids and any other possible spillages is required?

The correct detailing of the waterproofing system around any surface penetrations such as joints and holding down bolts for barriers or equipment is also critical for maintaining this chemical resistance over the entire surface, to ensure the required system durability and a long service life.

• Behaviour in Fire: There are currently no specific fire resistance regulations for car park deck coating systems, but in accordance with normal UK Building Regulations, the applied resin waterproofing systems should have good resistance to the 'surface spread of flame'. In enclosed or underground car parks, there may be additional Building Regulations applied, such as restrictions made on requirements for preventing / restricting any possible fire decomposition products, including the quantities of any toxic fumes that could be released from the deck surface treatments in the event of fire. Therefore it is necessary to assess what Building Regulations should be applied for the deck waterproofing systems behaviour in fire, in each of the different areas of each deck?

• Colour and Design: Is there a modern environmental deck colour design scheme in place in order to establish a specific ambience or upgrade and create an increased level of light and security in the car park? (these improvements are usually undertaken in conjunction with lighting upgrades and other user improvements in the facilities i.e. wall coatings, soffit coatings, signage and security etc.).

• Parking Deck Service Life / Durability / Maintenance: What is the desired service life and durability of the structure and the deck surfacing to first maintenance? How easy is it to close or restrict access to each area for maintenance purposes and possible re-waterproofing in the future? The durability required, plus the options and possibilities of future closure and maintenance, together with their associated costs are probably the biggest decisions for the car park owner.

• Parking Deck Waterproofing System Sustainability: Sustainability is quite rightly also now becoming an important issue for car park surfacing materials; basically this involves the assessment and reduction of the environmental impact of the systems including their raw materials source, their processing, installation, service life expectancy and their eventual recycling possibility. Sustainability also relates to waste reduction of materials used on site, together with the recycling versus disposal of their packaging.

• Waterproofing Penetrations through Car Park Decks: Any penetrations through the reinforced concrete decks, such as holding down bolts or brackets for barriers and equipment, handrails, plus connections around drainage details, etc. must also be assessed, correctly detailed and securely sealed to prevent water ingress.

Conclusions and Checklist for Deck Waterproofing System Selection:

To prepare the right proposals for your Car Park Deck Waterproofing requirements NCC Resin Flooring Site has adapted a simple ‘Check List for Car Park Deck Waterproofing System Selection’ that you can download and use to identify and define the best procedures and materials for success.

Additionally if you would like help and assistance with your specific project requirements, then please call any of our offices and one of our Resin Floor specialists will be delighted to assist you.
For FREE Expert Advice Call Any NCC Office and Our Basement Waterproofing Specialists will be Pleased to Help.

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