The Brew Cabin

Posted: **Thu Dec 20, 2007 3:15 pm**

Hi,

I mailed this question and Tony kindly replied - but I wondered whether any others had experienced this phenomenon (sorry for mailing and now posting):

When it's freezing cold, one or two of my Indian sandstone steps "clicks". I cannot detect any movement whatsoever - so I wondered if it was perhaps some kind of wicking and then internal freezing (or something!) and when I stand on it the stone compresses slightly and causes a "click".......! Or, am I just mad?!

The steps are made of brick risers, sandstone treads, and the sides are supported by Azobe sleepers (again, I wondered if it was the difference in materials and the way they behave when frozen, but I cannot detect any visible signs of movement). It feels, under foot, as if there is a "switch" under the sandstone slab that makes the click, not the actual slab itself rocking. The steps are formed in to a lawn, so there could be moisture present from the grass/soil.....

Having typed this, I am now slightly worried that I am going insane!!

Any input welcome,

Matt

Posted: **Thu Dec 20, 2007 5:03 pm**

It's the paving fairies taking the p*ss out of you.

Posted: **Thu Dec 20, 2007 5:23 pm**

I haven't noticed it with sandstone but I have with slate. I assumed that there is some degree of delamination in the slab which is sufficiently slim not to be noticeable normally. As long as the pointing is sound and the slab well bedded it's something I wouldn't worry about. In time the slab may well fully delaminate and need to be replaced.

I once did a job with sandstone that the client had bought cheap herself and noticed that some of the slabs were 'flimsy' and could well delaminate in the future. This was of course excluded from the guarantee!

Posted: **Thu Dec 20, 2007 6:12 pm**

Air contracts when cold and holds its moisture. obviously it doesn't freeze , or we would all drop dead,. all other gasses are held with the air. I suspect that the energy applied to the the slabs would be enough for the air to expand releasing other gasses thereby causing a click. Its like cracking your knuckles, the knuckles don't actually crack, its just the gas releasing. Who was it said "the world is a triangle?" :p

Posted: **Thu Dec 20, 2007 8:04 pm**

Hi Mattster

If your anything like me in the cold it's probably "YOUR" joints clicking and not the flags :p

Darren

Posted: **Fri Dec 21, 2007 2:10 am**

i like sean's explanation,sounds like one of those anomalies that you just have to get used to,it doesn't sound good ,but without movement what can you do?
LLL

Posted: **Fri Dec 21, 2007 2:02 pm**

Thanks everyone, I appreciate your replies.

I guess I was thinking more along the lines of the delamination that Rich H mentioned, but I am intrigued by Sean's suggestion!

Sean - do you mean air within the slab (back to delamination?) is having my (considerable!) force applied to it and is expanding and "clicking" (but when the air is warm it cannot / does not expand when said force is applied)?

Either way, since the slab appears to be well bedded and the pointing appears to be absolutely fine I presume I can relax a little and enjoy Christmas.....

Cheers one and all for your time,

Matt

Posted: **Fri Dec 21, 2007 5:09 pm**

kinetic energy.

Posted: **Sat Dec 22, 2007 6:59 am**

isnt it called a pavefart ????
Everyone blames me !!! now i can print this topic off and prove to them that it is a pavefart..
cheers

The Brew Cabin

Mysterious clicking..... - When it's freezing cold....slabs "click"