Experts in Concrete Patio installation

How to Fix Poor Drainage After a Bad Patio Installation

A patio that collects puddles, sends water toward your home, or stays soggy after rain is often the result of poor drainage planning. In many UK gardens, rushed or unprofessional installations fail to include proper fall, edge flow, or sub-base structure.

In this guide, we break down the common signs of a drainage issue, explain why they happen, and outline the best fixes to make your patio dry, safe, and long-lasting.

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What Causes Drainage Issues in Patios?

Water should always flow away from your home and off the patio surface quickly. If your patio holds water, drains poorly, or sends moisture toward buildings, one of these construction mistakes may be the cause.

Insufficient Fall or Slope

Concrete patios should have a gentle slope (typically 1:60) to allow water to run off the surface. If the patio is level or tilted back toward the house, water will pool or flow into your walls and foundation. Many bad installations skip this crucial grading step or fail to measure it properly.

Poor Sub-Base Preparation

Without a compacted, permeable sub-base, patios can settle unevenly or trap water underneath. This leads to soft spots, puddling, and long-term sinking. A proper sub-base should include layers of MOT Type 1 or similar material, compacted in stages to form a solid foundation with good drainage.

Blocked or Missing Edge Drainage

Patios near garden beds, fences, or structures need an outlet for water to escape. If edging is sealed with mortar or hard barriers, water has nowhere to go. In some cases, overflow gets forced under slabs or toward the property. Drainage channels, gravel borders, or open joints can help.

No Drainage Channels Installed

Large patios or those near homes may require dedicated channel drains or French drains. Without them, heavy rainfall simply sits on the surface or soaks into the wrong areas. This is especially important in clay soils or high-rainfall regions like much of the UK.

Settling or Movement Over Time

Even a well-built patio can develop drainage issues if the ground shifts or if heavy furniture compresses sections unevenly. This can cause small dips where water collects. These low spots often go unnoticed until they become puddles during wet spells.

Fixing a Badly Drained Patio

Adjust the Fall or Surface Level

Use levelling compound or remove and re-lay affected slabs to reintroduce proper slope.
A fall of 1:60 is standard, roughly 1cm drop for every 60cm of patio length.
This helps direct water away from buildings and toward a suitable drainage area.

Install Drainage Channels or Gravel Borders

Channel drains collect and redirect surface water, ideal along door thresholds or at the base of slopes.
Gravel strips or soakaway trenches can absorb overflow and reduce pooling on edges.
Ensure drainage runs toward gardens or storm-safe outlets.

Lift and Relay Sinking Sections

If poor sub-base prep is the issue, affected areas may need to be broken out and rebuilt from the ground up.
Recompact the foundation using proper base materials, and consider using geotextile membrane for added stability.
This ensures long-term drainage performance and prevents further movement.

Frequently Asked Questions

Pooling water, damp walls near the patio, moss buildup, and puddles that linger for more than 24 hours are all signs of poor drainage. Slopes should run away from your home.

Yes. Water flowing toward your home can seep into foundations or basements, cause damp problems, and create long-term structural issues. It should be addressed as soon as possible.

Not necessarily. If the drainage problem is isolated to one area, lifting and relaying that section may solve the issue. Full replacement is only needed if the entire installation was done poorly.

A standard fall is 1:60, meaning 1cm of drop for every 60cm of length. This gentle slope ensures water flows away without being noticeable underfoot.

In some cases, yes. Installing surface drainage channels, adding gravel soakaways, or regrading adjacent soil can help. But severe slope issues may require concrete to be lifted and adjusted.