Hollow Sound Basement 18" Tiles [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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10-04-2006, 05:46 AM
I have a guy installing 18" porcellain tiles in my basement over 10 year old concrete.

His first try 30% of the tiles had a hollow sound after 12 hours.

I pulled them up and there was less than 10% coverage on the back of each tile.

I also saw that his trowel marks were not being touched by the tiles.

He is using a 1/4 x 1/4 trowel.
He claims his mix was too dry.
He won't add an additive to the grey cheap thinset.
He claims hollow sound is fine.


Should I accept any hollow sounding tiles
(I think not)

Should I upgrade to a flexible mortar with any admix?

Can he switch to 1/2 x 1/2 trowel and push tiles down?

Should he butter each tile?

Thanks for a great forum...


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John K
10-04-2006, 05:59 AM
Fire him! He just doesn't know how to set tile properly. The cheap thinset will not stick well to porcelain.

Do some research on here and you'll see what it takes to do the job right. Remember, a cheap price will cost more in the long run. ;)

Dave Taylor
10-04-2006, 06:18 AM
A bit severe, I know but... it's your house and money.



Hollow sounding tiles: Accept none, nada, zip.

Use modified mortar: Yes indeed for the situation you describe.

1/2" x 1/2" x 1/2" square notch and push: Mebee' a bit large but yes.... just get some-one-else to do this.

Backbutter: Yep.

Having said all that...... I would worry that your cement floor was inspected (correctly) and deemed (correctly) to be suitable for ceramic, then prepared (correctly).

Search these forums using the word "concrete" and "cement" and "basement" for good concrete inspection and preparation criteria.

Any more questions.... just ask :---)

Good luck to you Dean.

John Bridge
10-04-2006, 02:36 PM
Hi Dean, :)

Sounds like your man has problems. Was he the low bidder? ;)

10-04-2006, 10:58 PM
Doesn't sound like this guy knows what he is doing. 1/2 x 1/2 trowel, backbutter without a doubt. Hollow sound means one thing. You are sure to have a serious problem very soon, especially with as little coverage as 10%.
If possible use a thinset product such as TEC Superflex or similar(Most man. make a thinset with extra adhesive properties specifically for tiles with lower absorbtion)for porcelain. It is expensive but will do the job.

10-05-2006, 06:47 AM
Just as I thought.

Thanks for all the advise.

This is a project that was seven years in the making.

Living in Greenwich CT, we don't get realistic prices and I have been resisting for years.

This guy has been our handyman for years, but this is a big project for him.

We have been checking with friends in the business and to show you how skewed it is, a contractor friend of ours just got a quote to tile a 12 foot by 12 foot room with the material furnished which was 8,000.00. There was nothing special about the site conditions.

Over twenty five Years ago I was in the business as an site engineer on the construction of a nuclear power plant so I can figure a few things out.

As he finishes the floor, I work on a 3,000 bottle wine rack with individual holders for each bottle. I figure I have 100,000 feet of painting 1x1 boards which I ripped from 1x8's

Thanks again...