No Comments Written by Sam on September 22, 2026. Posted in Concrete Floor

Protecting Car Park Decks from Winter Salt Damage

Every winter, cars drive into multi-storey and rooftop car parks carrying slush, grit and de-icing salt from the roads. Gritting also takes place on the decks themselves to keep ramps and walkways safe. That salt is one of the main causes of long-term damage to reinforced concrete car park structures. This article explains how salt damage happens, why deck coatings and waterproofing are the main line of defence, and what owners and facilities managers should check before and after the winter months.

How salt damages a concrete deck

Concrete looks solid, but it contains a network of tiny pores and, over time, cracks. When salty water sits on an unprotected deck, chlorides are carried into the concrete through those pores and cracks. This process is called chloride ingress. Repeated wetting and drying, especially on exposed decks, tends to concentrate the chlorides further over successive winters.

Corrosion of the reinforcement

Steel reinforcement inside concrete is normally protected by the alkaline environment around it. Once enough chloride reaches the level of the steel, that protection breaks down and the bar begins to corrode. Rust takes up more space than the original steel, so it pushes against the surrounding concrete and causes cracking and spalling. Pieces of concrete can break away from soffits and edges, exposing more steel and speeding the process up.

The difficulty is that this damage is largely hidden until it is well advanced. By the time rust staining, cracking or spalling is visible, chlorides may have travelled a long way into the deck, and repairs become more extensive and more disruptive.

Freeze-thaw and surface wear

Salt is not the only winter problem. Water that soaks into the surface can freeze and expand, gradually breaking up weak surface concrete. Snow ploughs, tyre wear and turning traffic on ramps add abrasion, which removes any surface protection that is already worn and leaves the concrete beneath more exposed.

Why deck coatings and waterproofing matter

The most effective way to slow down chloride ingress is to stop salty water reaching the concrete in the first place. Resin deck coatings and waterproofing systems form a continuous barrier on the surface, while also giving the slip resistance and wear resistance that a busy car park needs.

Car park systems are usually specified by deck level, because each level faces different conditions:

• Top decks are exposed to rain, frost and UV light, so they need a waterproof, UV-stable system that can cope with temperature changes and often some movement in the structure.
• Intermediate decks are covered but still see salty water dripping from vehicles, so they need waterproofing and good wear resistance in traffic lanes.
• Ramps and turning areas take the heaviest abrasion and need a high-grip, hard-wearing finish.
• Ground and lower decks may be on grade and face different moisture conditions from below.

Our car park systems can be applied to concrete, asphalt and polymer-modified cementitious screeds, and provide slip resistance, chemical resistance, wear resistance and a UV-stable finish. Different colours can also be used to separate parking bays, pedestrian walkways and traffic aisles, which helps with safety and wayfinding.

Preparation and repair before coating

A coating is only as good as the deck underneath it. Before a new system goes down, damaged and contaminated concrete has to be dealt with. On car park decks this typically involves:

• Captive shot-blasting or grinding to remove old coatings, oil, rubber and weak surface material
• Breaking out and repairing spalled or delaminated concrete
• Treating exposed reinforcement as part of the concrete repair
• Repairing cracks and detailing movement joints so they stay watertight
• Checking falls and drainage so water does not pond on the deck

Ponding water is worth special attention. Low spots that hold salty water through the winter are often where damage starts, and correcting falls or improving drainage at outlets can make a real difference to how long the deck lasts. Our surface preparation page explains our approach to getting substrates ready for resin systems.

Inspection: what to check each year

A regular inspection regime helps catch problems while they are still small. Structural assessments of car parks should be carried out by a suitably qualified engineer, but facilities teams can also keep an eye out for early warning signs. Autumn, before gritting starts, and spring, once the worst weather has passed, are good times to look.

1. Coating condition. Look for worn traffic lanes, cracking, blistering or areas where the coating has lifted, particularly on ramps and at entrances.
2. Cracks and joints. Check movement joints for failed sealant and look for new cracks in the deck surface.
3. Rust staining and spalling. Brown staining, hollow-sounding areas or loose concrete, especially on soffits and edges, can indicate corrosion of the reinforcement.
4. Drainage. Make sure gullies and channels are clear and that water is not standing on the deck after rain.
5. Line marking. Faded bay markings, arrows and pedestrian routes affect safety and are often a sign that the surface beneath is worn too.

Small areas of damaged coating can often be repaired locally before winter, which is far less disruptive than waiting for a larger refurbishment later.

Keeping the car park open during works

Most car parks need to stay in use during refurbishment, so works are normally phased level by level or bay by bay, with temporary marking and traffic management. Cure times also need planning. As a general guide, we recommend waiting at least 48 hours before allowing vehicular and heavy traffic onto a newly installed system, and 16 to 24 hours for pedestrian traffic, although this depends on the system and the temperature.

For multi-level structures, our multi-storey car park flooring page covers deck coatings, ramps, line marking and resurfacing in more detail.

Frequently asked questions

Why does road salt damage car park decks?

Road salt contains chlorides that are carried into the concrete by water. Once chlorides reach the steel reinforcement, they break down its natural protection and cause corrosion. The rusting steel expands, cracking and spalling the concrete, which can lead to costly structural repairs if left untreated.

How do you protect a car park deck from salt?

The most effective protection is a continuous waterproof deck coating that stops salty water reaching the concrete. This should be combined with good drainage so water does not pond, sound joints and crack repairs, and regular inspections so worn areas of coating are repaired before winter.

How long before cars can use a newly coated car park?

As a general guide, we recommend waiting at least 48 hours before allowing vehicles and heavy traffic, and 16 to 24 hours for pedestrians. The exact time depends on the system used and the temperature during installation and curing.

When is the best time to refurbish a car park deck?

Many resin systems are easier to install in milder, drier weather, so spring to early autumn is often preferred, particularly for exposed top decks. Carrying out repairs before winter also means the deck is protected before gritting begins.

If your car park is showing signs of wear or salt damage, call us on 01782 865099 or request a quote to arrange a survey of your decks.

Written by Sam on August 12, 2023. Posted in Concrete Floor

How Long Does Screed Take to Dry?

The wait is on. You’ve just had a new floor screed laid, and now the question on everyone’s mind is: when can we walk on it? When can we install the final floor covering? Unfortunately, there’s no one-size-fits-all answer to “how long does screed take to dry?”. Several factors influence drying times, and understanding them is crucial for effective project planning.

At Optimum Flooring Services, we take pride in delivering exceptional flooring solutions and transparent communication. In this blog, we’ll delve into the world of screed drying times, exploring the key factors at play and offering guidance on what to expect.

Understanding Screed Types and Drying Rates:

The type of screed material used significantly impacts drying times. Here’s a breakdown of some common screeds and their drying characteristics:

Traditional Sand & Cement Screed: This workhorse of the screeding world offers good strength and durability but has a relatively slow drying time. Typically, traditional screeds require 1mm of drying per day for the first 50mm, followed by an increasing drying time for each additional millimetre. A 50mm thick traditional screed, under ideal conditions, might take around 2 months to dry fully.

Fast-Drying Screeds: Modern screed formulations incorporate additives that accelerate the drying process. These screeds can achieve drying rates of 10-15mm per day, significantly reducing waiting times. However, they may come at a slightly higher cost compared to traditional screeds.

Liquid Screeds: These self-levelling screeds offer a smooth finish and faster drying times compared to traditional screeds. They can achieve drying times as low as 1mm per day, with some formulations reaching full walkability within 24-48 hours.

Beyond Material: Factors Affecting Drying Time

While screed type plays a major role, other factors also influence drying times:

Thickness of the Screed: As a general rule, thicker screeds take longer to dry. The increased volume of material requires more time for moisture to evaporate.

Ambient Conditions: Temperature and humidity significantly impact drying rates. Warm, well-ventilated environments promote faster drying. Conversely, cold or humid conditions can slow down the drying process considerably.

Subfloor Characteristics: A porous subfloor like concrete allows moisture to transmit upwards, aiding in drying. However, a non-porous subfloor like vinyl may require additional measures like a DPM (damp-proof membrane) to prevent moisture from becoming trapped beneath the screed.

Optimum Practices for Faster Drying:

Maintain Good Ventilation: Ensure proper airflow throughout the space during the drying process. Open windows and doors whenever possible, and consider using fans to circulate air.

Control Temperature and Humidity: If possible, maintain a moderate temperature (around 15-20°C) and control humidity levels (ideally below 65%). Dehumidifiers can be helpful in achieving these conditions.

Cover the Screed (Partially): While complete exposure promotes drying, covering the screed loosely with breathable membranes can help prevent rapid drying and minimise the risk of cracks.

When Can You Walk on the Screed and Install Floor Coverings?

The answer depends on the type of screed, its thickness, and drying conditions. Here’s a general guideline:

Walking: For traditional screeds, waiting at least 48 hours is recommended before walking on the surface. Fast-drying screeds and liquid screeds might allow for foot traffic sooner, depending on the specific product. Always refer to the manufacturer’s recommendations for your chosen screed material.

Floor Coverings: Installing floor coverings like tiles or wood requires a completely dry screed. The residual moisture content (RMC) needs to be within the acceptable range specified for the chosen floor covering. Moisture meters can be used to measure the RMC of the screed.

Partner with Optimum Flooring Services for Expert Advice

At Optimum Flooring Services, we understand the importance of accurate drying time estimations for successful project planning. Our experienced team can assess your specific project requirements, including screed type, thickness, and desired timeline. We can then provide you with a realistic timeframe for screed drying and advise on any necessary measures to optimise the drying process.

Contact us today for a free consultation and let’s ensure your floor screeding project runs smoothly and efficiently.

No Comments Written by Sam on August 11, 2026. Posted in Concrete Floor

Why Concrete Moisture Testing Matters Before Resin Flooring

Moisture in the concrete is one of the most common reasons a resin floor fails early. The floor can look perfect on handover, then weeks or months later blisters appear, the coating starts lifting at the edges, or whole sections debond. In most cases the problem was in the slab before the first coat went down. This article explains why concrete moisture testing matters, how it is done, and what the options are when a slab is too damp.

Why moisture causes resin floors to fail

Concrete is porous and holds water long after it looks dry. New slabs contain mixing water that takes a long time to leave, and older slabs can draw moisture up from the ground if there is no effective damp-proof membrane underneath. Resin floors are largely impermeable, so when they are laid over a damp slab the moisture has nowhere to go.

Osmotic blistering

Osmotic blistering happens when moisture is drawn through the concrete towards the underside of the resin. Soluble salts in the concrete and at the bond line create pressure differences that pull water in, and over time this builds into liquid-filled blisters. They often start small and grow, and when they are cut open they may contain a liquid that can be alkaline. Once osmotic blistering has started it is rarely solved by patching the blisters alone.

Delamination and poor adhesion

Even without blistering, too much moisture at the surface can stop the primer bonding properly in the first place. Some resins react with water during cure, leaving a weak layer at the interface. The result is a floor that sounds hollow when tapped, peels at edges and joints, or breaks up under traffic.

How concrete moisture is measured

There are several ways to check moisture, and they do not all tell you the same thing. A reliable assessment uses the right method for the job and takes readings in enough places to represent the whole floor.

Relative humidity (hygrometer) testing

The method most commonly referred to in UK flooring guidance, including the BS 8203 and BS 8204 series of standards, is relative humidity (RH) testing with a hygrometer. An insulated hood is sealed to the surface, or a probe is placed in a drilled hole, and left until the air inside reaches equilibrium with the concrete. The RH reading reflects how much moisture the slab is likely to release into a sealed covering. Readings need time to stabilise, so this is not a five-minute test, but it gives a far better picture than a quick surface check.

Many resin manufacturers set a maximum RH for their standard primers, often around 75%, although limits vary by product. The manufacturer’s data sheet is always the reference point for the system being installed.

Surface moisture meters

Handheld meters that read moisture at the surface are useful for a quick comparison between areas, for finding damp patches, and for deciding where to place hygrometers. On their own they are not a substitute for RH testing, because they only see the top few millimetres and can be affected by salts, reinforcement and surface finishes.

Other checks

A survey should also check air and slab temperature, humidity and the dew point, as condensation during application causes similar adhesion problems. It is worth asking how old the slab is and whether it has a membrane underneath.

Why the concrete itself matters

Moisture testing goes hand in hand with checking the quality of the slab. Weak surface concrete, heavy laitance, contamination from oils and old coatings, or poorly finished new concrete all affect how a resin floor will bond and perform. We cover this in more detail in our article on the importance of quality concrete for your resin floor.

What if the slab is too damp?

A high moisture reading does not always mean the project has to wait. The options depend on the programme, the cause of the moisture and the system being installed.

• Allow more drying time. For new slabs, time with good ventilation and heating may be enough, but drying can be slow, particularly for thicker slabs.
• Use a damp-proof membrane (DPM) primer. Specialist epoxy DPM primers are designed to go down on concrete with higher moisture levels and suppress moisture before the main system is applied. They are often finished with an aggregate scatter to give a mechanical key for the following layers.
• Choose a breathable or moisture-tolerant system. Some systems are designed to cope better with moisture vapour, though they still have limits.
• Deal with the source. Leaks, poor drainage or a failed membrane under the slab need investigating, as no coating will overcome a constant supply of water.

In our own projects, DPM primers with an aggregate scatter are a regular part of the build-up under polyurethane screeds, particularly in food production and brewing areas where the slab and the environment are often damp.

Testing as part of proper preparation

Moisture testing should sit alongside the rest of the preparation process: mechanical diamond grinding to remove laitance and contamination, repairs to cracks and joints, and checks on the strength of the surface. You can read about how we approach this on our preparation page. Getting these steps right is far cheaper than lifting and replacing a failed floor.

If your existing resin floor is already blistering or lifting, our guide on how to repair resin flooring explains the common causes and the repair options. Where moisture is the cause, it needs to be dealt with as part of the repair, otherwise the same problem is likely to return.

Frequently asked questions

What moisture level is acceptable for resin flooring?

Many resin primers are limited to a relative humidity of around 75%, measured with a hygrometer, but the limit depends on the product. Always check the manufacturer’s data sheet. Where readings are higher, a damp-proof membrane primer or a moisture-tolerant system may allow work to go ahead.

What causes blisters in a resin floor?

Blisters are most often caused by moisture or osmotic pressure building up beneath the resin. Moisture moves through the concrete and is trapped by the impermeable coating, forming bubbles that can grow and fill with liquid. Contamination, poor preparation and application in cold or humid conditions can also contribute.

How long does concrete need to dry before resin flooring?

There is no fixed time. Drying depends on slab thickness, the concrete mix, temperature, ventilation and whether there is a membrane underneath. Rules of thumb are unreliable, so the slab should be tested with a hygrometer before work starts rather than relying on its age alone.

Can resin flooring be laid on damp concrete?

Not with a standard primer. On damp concrete, a specialist epoxy damp-proof membrane primer can be applied first to suppress moisture, followed by the chosen flooring system. The source of the moisture should still be investigated, especially if water is entering from below or from leaks.

If you are planning a new resin floor and want the slab assessed properly before work starts, call us on 01782 865099 or request a quote to arrange a site survey.

No Comments Written by Sam on February 21, 2023. Posted in Concrete Floor

The importance of quality concrete for your resin floor