The Drummy Slab: Why Your Porcelain Patio Sounds Hollow Underfoot

Your new porcelain patio looks spot on.

Straight joints. Clean cuts. Nice expensive slabs.

Then you walk across it and hear it.

Clunk.

One slab sounds completely different from the others. Hollow. Almost like there's nothing underneath it.

A few months later the pointing around that slab cracks.

Then the corner starts moving under your boot.

The porcelain isn't the problem.

It's what the bloke underneath it didn't do.

The Slab Shouldn't Be Floating

Porcelain paving needs proper support underneath it.

Not four blobs of mortar shoved under the corners.

Not five big dollops and a prayer.

A proper full mortar bed.

The idea is simple. The underside of that slab needs solid, consistent contact with the mortar supporting it.

When someone starts spot bedding porcelain, they're leaving empty pockets underneath.

You can't see any of that once the slab goes down.

From above, it can look absolutely perfect.

That's what makes it such a good cowboy shortcut.

Give It a Tap

A badly supported slab will often grass itself up.

Tap across a properly bedded patio and you should hear a fairly consistent solid sound.

Then you hit one badly bedded slab.

Donk.

Completely different.

That's the hollow or "drummy" sound people notice on new patios.

Now, sound alone doesn't automatically mean the patio is about to collapse. Different conditions can change how paving sounds.

But if you've also got movement, cracking joints or loose slabs?

Now we're interested.

Something underneath isn't doing its job.

Those Empty Pockets Cause Trouble

A 20mm porcelain slab is strong.

But it still needs support.

Leave big voids underneath and the load isn't being spread evenly through the mortar bed.

Put a heavy table leg over the wrong spot.

Drop something.

Keep walking over an unsupported section.

You're asking that slab to bridge an empty space it was never supposed to bridge.

Water can also find its way into poorly constructed areas underneath.

Then winter turns up.

Now you've got moisture, movement and unsupported paving all working together.

Eventually something gives.

Sometimes it's the joint.

Sometimes the bond.

Sometimes the slab itself.

Porcelain Needs to Actually Bond

There's another part cheap installations miss.

Porcelain is extremely dense.

That's one reason it's brilliant outside.

It's also why you can't treat it like an old concrete paving slab.

The back needs proper preparation with a suitable bonding slurry or primer before it goes onto the mortar bed.

Skip that and you can have a lovely full bed of mortar underneath while the porcelain itself hasn't properly bonded to it.

The mortar stays down.

The slab comes up.

We've seen them lift surprisingly cleanly.

That's not clever engineering.

That's an expensive paving tile sitting loose on some cement.

Pointing Won't Hold a Bad Patio Together

This is where people try to repair the wrong thing.

Joint cracks.

Someone scrapes it out and repoints it.

Three months later it's cracked again.

Of course it has.

Pointing isn't there to hold a loose slab down.

If the paving underneath is moving, the joint is simply showing you the movement.

Fix the bedding.

Then fix the joint.

Not the other way around.

The Important Bit Disappears

This is the annoying thing about good porcelain patio installation.

The most important work gets covered up.

Proper sub-base.

Correct mortar.

Full bedding.

Bonding slurry.

Falls.

Drainage.

Then £10,000 worth of porcelain goes over the top and nobody ever sees the work underneath again.

That's exactly why it's such an easy place for cowboys to save time.

We don't.

Because we'd rather your patio sounded boringly solid under your boots than get a phone call next winter because the pointing is cracking and the slabs are rocking.

Stop letting cheap builders ruin your property. Pop down and see the lads at 78 Alma Rd, Bournemouth BH9 1AN, UK, or ring the site phone on 07840151036.