Multi-storey and podium car parks are hard places for a sealant joint. The deck moves with temperature and load. Tyres roll over the joints all day. In winter, de-icing salt is carried in on wheels and washed into every gap. When the seal fails, salty water reaches the concrete and steel below. This guide is for car park operators, estates teams and FMs responsible for deck and ramp joints.
Where the joints are
- movement joints across the deck, which let sections of slab expand and contract
- construction joints, where pours of concrete meet
- joints at ramps, where the slope meets the level deck
- joints at upstands, kerbs, columns and walls
- joints on podium decks above occupied space, such as shops or offices
Some car parks also have proprietary expansion joint systems with metal or rubber components. Those are a separate product and are maintained to the supplier’s guidance.
Why they fail
Car park joints fail for the same basic reasons as other joints, but faster. Repeated movement stretches the sealant. Tyre loads and turning wheels abrade the surface and tear at the edges. Grit and debris get pushed in. De-icing salt and standing water attack the joint edges. Once a seal opens up, water and grit get in, the arrises can spall, and the damage spreads along the joint. Our guide to why expansion joints fail covers the causes in more depth.
What a reseal involves
The failed sealant and any loose material are cut out. The joint faces are cleaned back to sound, dry concrete. If the edges are broken, we’ll tell you if they need repairing before sealing, because sealant needs a firm face to bond to. A backing rod is fitted to set the depth, a primer is applied where the manufacturer specifies one, and a trafficable sealant of the right movement class is installed and tooled. PU sealants are common on decks because they resist abrasion. See our expansion joint sealing service.
Need the work done? Mastic Doctor covers South East England, London and all of Scotland, with a 12-month guarantee on our workmanship. Send details for a fixed quote.
Keeping the car park open
Closing a whole car park is rarely an option. Work can be phased by level, bay or lane, with cones and signage, so parking continues elsewhere. The sealant also needs time to cure before traffic runs over it, so each phase has to allow for that. Tell us your site hours and access windows and we’ll plan around them. Dry weather matters for open top decks, as the joint must be dry and within the product’s temperature range (see weather and sealant).
Inspection habits that help
Joints are easier to look after if someone checks them regularly. A walk of each level after winter, looking for open joints, missing sealant, debris and water marks on the soffit below, will catch most problems early. Note any leaks onto vehicles or into spaces below the deck, and record where they are. Fold the car park into your planned maintenance programme rather than treating each leak as a one-off.
Podium decks over occupied space
Podium decks sit above shops, offices or flats, so a failed joint can leak straight into someone’s space below. Leaks there are often reported first by the tenants underneath. Treat these joints as a priority in any programme, and check them after heavy rain. Where a podium has a waterproofing layer beneath the surface, the sealant joint is only part of the picture, and the deck’s designer or waterproofing specialist should be involved.
Quick answers
Can car park joints be sealed in winter?
Sometimes, on dry days within the product’s temperature range. Frost, damp joints and cold mornings often stop external work, so spring to autumn is easier to plan for open decks.
How soon can cars drive over new sealant?
That depends on the product, the temperature and the bead size. The data sheet gives guidance, and we’ll confirm the restriction time for the product used before each area reopens.
Do you repair broken joint edges?
We’ll tell you if the edges need repairing before sealing. A sealant can only perform if it bonds to sound, firm faces on both sides of the joint.
Related services
- Expansion and movement joint sealing
- Industrial and floor joint sealing
- Commercial sealant contractors
More advice
- Why Expansion Joints Fail and How to Fix Them
- Weather and Sealant: When Work Can Go Ahead
- Planned Sealant Maintenance for FMs
- Warehouse Floor Joints: Stopping the Damage
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.