How to check for voids under tiles

[smurfitt]

Another piece of advice given to me is to check this by tapping the tile with my knuckles.
When I tap the middle, most tiles sounds solid but off centre on some I get a sort of hollow sound.
Majority of the hallway tiles sound hollow in the middle.
Any cause for concern?
What will happen?
How to rectify?

Thankyou for any advice.

[Sir Ramic]

Were you able to see what method was used to fix these tiles. Sounds as if they have been dot and dabbed ???

[smurfitt]

They spread the adhesive on the floor then combed it and placed the tile down and hit it with open palm.

[Sir Ramic]

Then in theory it should be fine but it would take an experienced fixer a site visit to say anymore on this matter really.

[mikethetile]

tiles can sound hollow if tapped which is why it takes an experianced ear to tell the difference

but if its a concrete subfloor with 100% addy coverage then the tiles wouldnt normally sound hollow if tapped

[doug boardley]

what is the subsrate in the hallway?

[smurfitt]

Thanks for response, both floors are concrete.

[user123]

Same on our floor!! I did the setting out in the hall and kitchen, hubby did the adhesive spreading and laying the tiles, no dot and dabbing, but boy do these tiles sound hollow, horrible. Some in the middle, some in the corners... concrete underneath but not very even, granted... we didn't know about SLC then. Is that to blame? Looks fine, sounds awful.

[whitebeam]

Could the tiles have bowed in the firing process which gives a hollow in the centre

[Dave]

The higher the sound pitch the more solid they are and the deep hollow sound means not so well bonded.

[doug boardley]

crOft will have a looksee

[timeless john]

The higher the sound pitch the more solid they are and the deep hollow sound means not so well bonded.

Do you always get a blind bloke in to check your tiling?
My parents used to get their piano tuned this way.

[doug boardley]

Do you always get a blind bloke in to check your tiling?
My parents used to get their piano tuned this way.

Ray Charles?

[user123]

The higher the sound pitch the more solid they are and the deep hollow sound means not so well bonded.

Wow, Dave, that is really useful, thanks!!