Raised Patio Against the House: Avoiding a Bridged Damp Course

What the Damp Proof Course Does, and How to Find It

Every house built to modern standards has a barrier built into the walls, usually a few brick courses above ground level, whose job is to stop ground moisture climbing into the brickwork and, eventually, into your home. That's the damp proof course, or DPC, and it isn't decorative. Without it, moisture would climb steadily up the wall by capillary action, the way water climbs a paper towel dipped in a saucer.

On most houses you can find it yourself. Look at the brickwork close to ground level for a horizontal line in the mortar that looks slightly different from the courses above and below it, or a visible strip of black or grey material sandwiched between two brick courses.

It isn't always easy to spot. Rendered walls, older properties and houses that have been reclad can hide it from view, and some genuinely old buildings never had one fitted in the way we'd expect today. If you can't identify it with confidence, that's a job for someone who can, not a guess.

What Bridging Means, and Why It Matters

Bridging happens when raised soil, a flower bed, decking or paving is built up against the wall to a height that reaches or covers the DPC line. Once the ground or paving sits level with or above the barrier, you've given moisture a route straight past it and into the brickwork above.

The damage rarely shows outside at all. It usually appears as a damp patch on an internal wall, sometimes with a musty smell or flaking plaster at skirting height, often a year or more after the work was done. Putting it right generally means taking up the offending paving and re-establishing the clearance, occasionally alongside plaster repairs, and none of that is cheap. It's also entirely avoidable. The same clearance principle protects air bricks near ground level too, worth reading about separately if your plans go anywhere near one.

The Rule That Matters

Here's the principle, and I won't pretend to give you a number I don't have. Paving and finished ground level need to sit clear below the damp proof course by a margin, and that clearance is set by Building Regulations and established good practice, not a figure I could quote in a blog post. The exact distance depends on your wall construction, the paving detail and the drainage arrangements, and it needs confirming for your specific house rather than taken from anything you've read online, including this. If a contractor gives you a number without having looked at your wall, ask more questions, not fewer.

So Can You Have a Raised Patio? Yes, Done Properly

This is the part that matters to you, so I'll say it plainly: a level, raised patio against the house is genuinely achievable. It just needs designing properly at the point where paving meets wall, rather than simply built up to the height you fancy. There are several approaches I use, depending on the site.

Keep It Down, With a Drained Margin

Often the best answer is to keep the paving comfortably below the DPC and deal with the step by softening it, not raising the patio to meet it. A narrow gravel or shingle margin against the wall, or a discreet channel drain running along the house side, keeps rainwater and splash-back away from the brickwork without ever touching it at the wrong height.

Bring It Up, But Hold It Away From the House

Where a raised, level surface really is the goal, it can be built up, but it needs to stop short of the wall, with a gap and a proper drainage detail between paving and brick rather than running straight up against it. That gap does the same job as the gravel margin: it stops the paved surface and the wall ever meeting at a height that matters.

Sometimes the Honest Answer Is a Small Step

Not every threshold can be made level without compromise, and I'd rather say so than pretend otherwise. Sometimes the better design is a shallow, well-proportioned step in a non-slip material, rather than a level surface that puts the wall at risk. A step doesn't have to feel like an obstacle if it's designed with intent.

A Genuinely Level Threshold Needs a Builder

If what you actually want is a true, flush threshold straight from the kitchen onto the patio, that's achievable too, but it's a building detail, not a paving one. It typically involves a drainage channel set into the floor at the doorway and changes to the door and flooring build-up, and it needs a builder working alongside the design. I'd rather tell you that now than have you find out halfway through a project. I've written elsewhere about designing seamless indoor and outdoor paving without compromising the wall behind it, and that's worth reading alongside this if a flush threshold is what you're after.

Retaining the Raised Area

If any part of the new patio sits above the surrounding ground, something has to hold it up, and that's a retaining structure with its own rules around drainage and stability, and sometimes Building Control. It's a subject in its own right, one I'll cover separately, but worth knowing now: a raised patio and a retaining wall are usually a package deal, not two separate decisions.

If It's Already Been Done

If you're reading this because paving or a raised bed is already hard against your house and you're worried, don't panic, and don't start digging it up on a Sunday afternoon. Bridging is a common problem and it's usually fixable. Get someone qualified to look at the wall and the ground level together, rather than assume the worst, or assume it's fine. A damp patch inside doesn't always mean bridging, and bridging doesn't always show up as damp straight away. Either way, a proper look beats a guess.

Conclusion

The level, indoor-outdoor patio most people want against their house is genuinely achievable, and there's no reason to give it up. What decides whether you end up with a beautiful new space or a damp problem eighteen months later is the detail at the wall, not the ambition itself. Get that detail right and everything else about a raised patio is simply good design.

If you're planning a patio against the house and want the levels thought through properly from the outset, that's exactly the kind of detail I like to get right before anyone picks up a spade.