Experts in Concrete Patio drainage and compliance

How to Fix a Patio That’s Higher Than Your Damp Proof Course

When a patio is laid too high, especially above the damp proof course (DPC), it creates a serious risk of moisture bridging into the walls of your home. This can lead to internal damp, mould, and even structural damage over time.

In this guide, we explain how to spot if your patio is breaching the DPC, why it’s a problem, and what practical solutions you can use to fix or isolate the issue without a full rebuild.

Free quote More topics

Why a High Patio Causes Damp Problems

UK building regulations require the external ground level to sit at least 150mm (two bricks) below the DPC. If your patio breaches this, here's what could go wrong.

Moisture Bridging into Brickwork

The most common issue is moisture soaking into the wall from below. When your patio sits level with or above the DPC, rainwater can travel up and into the masonry via capillary action. This bypasses the protection the DPC provides, leading to rising damp inside the home.

Penetrating Damp from Splashback

Hard surfaces reflect rainwater back onto the wall. If there's not enough clearance, water can splash above the DPC line and be absorbed higher up. This is especially common in exposed patios during heavy UK rain, worsening damp patches and even affecting internal plaster or insulation.

Blocked Air Bricks or Sub-Floor Vents

A raised patio often covers air bricks, which are vital for ventilating suspended timber floors. Blocking them causes condensation to build up below your floorboards, increasing the risk of rot and mould. It also affects the overall breathability of your home’s foundations.

Non-Compliance with Building Regulations

In the UK, patios should not be constructed above the DPC unless a cavity tray or other moisture management solution is installed. If your patio was added without consideration for the DPC, it may fall short of current building standards, which can cause issues when selling your home or during property surveys.

Trapped Water Against the Wall

Without proper drainage, a high patio edge can cause water to collect directly against your home’s foundation. This constant contact accelerates deterioration of mortar joints and increases the likelihood of long-term water damage and frost-related cracking.

Ways to Fix a Patio That’s Too High

Lower the Patio Level

The most thorough fix is to remove the patio and relay it at the correct height, 150mm below the DPC.
This involves breaking up the existing slab, adjusting the sub-base, and re-pouring or laying new materials to correct depth and slope.
It’s labour-intensive but restores full compliance and long-term safety.

Add a Drainage Channel Along the Wall

If relaying isn’t possible, install a narrow linear drain or French drain between the wall and patio.
This collects and redirects water away from the house and helps break the capillary path to the wall.
Make sure the channel is sloped properly and backfilled with clean aggregate or protected with a drain grille.

Install a Vertical Damp Barrier

Use a vertical DPC membrane or tanking slurry applied to the wall where the patio meets it.
This creates a waterproof surface that blocks water penetration from the patio into the brickwork.
Can be used alongside other fixes, such as drainage or surface sealing.

Uncover or Extend Air Bricks

If air bricks are buried, carefully excavate a recess in the patio to expose them.
Use air brick extension sleeves or grille boxes to maintain airflow while preventing water ingress.
Never fully block or cover air bricks, especially in suspended floor properties.

Consult a Surveyor for Damp Diagnostics

If damp is already visible inside, have a qualified surveyor inspect the property.
They can determine the extent of moisture ingress and recommend whether internal DPC injection or further patio alterations are necessary.
Great for peace of mind when buying or selling a property.

Frequently Asked Questions

Check the brickwork on your home. The DPC is usually a visible line or change in brick colour about two bricks (150mm) above ground level. If your patio meets or covers this line, it's too high.

Sealing can help in the short term but won’t solve deeper moisture ingress. It’s best used alongside proper drainage or physical barriers, not as the only solution if the patio is too high.

It could be flagged as a potential defect. Most surveyors will note patios that breach the DPC or block ventilation, which can impact property value or sale negotiations.

It isn’t recommended and may breach UK building guidance. Any patio that doesn’t maintain a 150mm gap should include damp protection, drainage, and ventilation allowances.

Yes, a gravel soakaway trench can improve drainage and reduce splashback. It’s a temporary measure but can be useful while planning a more permanent solution.