[Paul79]

Been sent a couple of photos of these Indian stone flags customer said they've been sealed but salt is starting to show through. Flags laid 3 years ago sealing was done last year. Wants cleaning/resealing. Happy to pass it on it's up Standish/Wigan send me a message as I don't do sealing.

[Slacky]

Who sealed them?

What makes you think that's salt coming through?

[Paul79]

Who sealed them?

What makes you think that's salt coming through?

Got no idea on that mate it was the customer that said salt is coming through I don't have a clue about sealing to be honest.

[Smudger]

if its salt then re-sealing won't help it requires stripping

at a guess it looks like  areas of cement bed underneath are drawing salts up into the stone - maybe it was sealed too quickly before  the stone had time to release the salts

if not and its been laid badly this could be an ongoing problem

Darran

[Splash & dash]

A job to avoid at all costs I think 😬😬

[Jonny Swirljet]

I'd be tempted to suggest to the customer that because of this anomaly, you'd be happy to just to jet wash the stones, maybe use some hypo then see what happens to the surface throughout the coming summer months. If this procedure solves the problem then repeat the process next summer and seal it with good quality sealant, say, the all purpose sealant products Spinaclean sell.     

[Kev Martin]

Been sent a couple of photos of these Indian stone flags customer said they've been sealed but salt is starting to show through. Flags laid 3 years ago sealing was done last year. Wants cleaning/resealing. Happy to pass it on it's up Standish/Wigan send me a message as I don't do sealing.

Talk to the customer at length and find the history of what’s been done to it thus far.  That’ is in my opinion efflorescence albeit minor.  If so it needs dry brushing with an SIC brush on a mono rotary machine leaving for a week or so then check it.  If it’s OK clean it and then seal it with a Water Based Enhancing MVT ( breathable) sealer.

[the king]

Looks like it was sealed  when still bit damp !

[Slacky]

Looks like it was sealed  when still bit damp !

Thats what I was wondering.

[Kev Martin]

Looks like it was sealed  when still bit damp !

Thats what I was wondering.

Not to me as the efflorescence would be more prevalent around the grout.  I think it was laid on wet mortar without a dpm.

[Slacky]

D'you mean a damp-proof membrane?

[Kev Martin]

Yes

[Smudger]

Yes

get with the lingo slacky - p/w - wfp - Hypo - ADCOMSUBORDCOMPHIBSPAC - wtf 

Darran

[Slacky]

DPMs on patios is new to me. When I was landscaping this wasn’t something that was done, never been aware of it before.

[Kev Martin]

DPMs on patios is new to me. When I was landscaping this wasn’t something that was done, never been aware of it before.

So you were one of the Landscaping lot that has been contributing to my company funds over the last 15+ years or so

A bit like all the  so called Tilers who think that a heavy use shower  doesn’t need any tanking prior to tiling

[Slacky]

Ive looked online on installing a DPM for patios, can't find anything.

The purpose of a DPM, so far as Im concerned is to keep damp from rising up the walls and floors of a property. But this doesn't apply to patios surely...


Have you got any links which explain this please?

[Splash & dash]

I have never seen or Hurd of a dpm being used on patios regardless of there construction, a guy down the road from me dies all kinds of hard surfaces so I spoke to him about this and he said it’s not needed and in 35 years he has never had a problem, so ime a bit confused why you say it’s needed , Indian sandstone is a natural product and it wouldn’t have any membrane before it’s dug out of the ground and no councils that I know that have extensively used this ever put one down and they don’t get problems.

[Kev Martin]

I have never seen or Hurd of a dpm being used on patios regardless of there construction, a guy down the road from me dies all kinds of hard surfaces so I spoke to him about this and he said it’s not needed and in 35 years he has never had a problem, so ime a bit confused why you say it’s needed , Indian sandstone is a natural product and it wouldn’t have any membrane before it’s dug out of the ground and no councils that I know that have extensively used this ever put one down and they don’t get problems.

This reply is for both  you and Slacky.  I never said you needed a DPM to lay a patio I said it looks like efflorescence due to the fact a DPM wasn’t used.
Slacky if you are an experienced Landscaper you will know  that laying a patio is relatively easy as long as you follow the rules.  So prepare the surface, get your hardcore down, compact it level / ish,  then use a fairly DRY MORTAR / CEMENT MIX.  Lay the slabs, tamp them down level,  mix a dryish/ apple crumble type grout and sweep it in to the grout joints .  Run a hose ( appropriate to the width of grout joint) down the grout joints to smooth them and force the excess moisture out so it’s smooth, seal it with a water based impregnating sealer and it’s job done.

The mistakes are made when people  with virtually no  or very little knowledge start getting involved because they believe they are the next Alan Titchmarch or Capability Brown when deep down they know virtually SFA.  So they prep or what they think is a well prepped surface , mix a load of wet mortar and slap the slabs down.  Then they usually grout with a wet grout and leave that all the grout haze over the surface as well.  It is they who should be using a DPM because invariably the cement mixture is the wrong ratio, this causes the water to mix with the ground salts then it climbs up through the slabs and lo and behold efflorescence. 
I am sure you have both seen new build houses with the walls covered in white efflorescence?  It’s the same thing idiots trying to build with the wrong ratio mortar.
So IMO  You don’t need a DPM if your experienced. Sadly lots aren’t and if they used a DPM it would most likely reduce or even eliminate the efflorescence because the wet mortar wouldn’t really have the ground salts only those in the badly mixed mortar.  However personally I wouldn’t let them near my Lego let alone my Patio.

[Slacky]

I would never brush a dry mix in to point up a patio. Always a wet mix. Brushing in is likely to create its own problems. Particularly when laying a sandstone patio as the gaps between the slabs are much bigger than regular sized slabs.

I find it odd you say this issue has occurred because a DPM wasn’t used. Show me a patio with a DPM, I’ve never seen one in the 11 years I was a landscape foreman, whether the patio was laid by a novice or an experienced landscaper. I think these kinds of beliefs profligate in the same waythat window cleaner folklore encourages ridiculous statements about ladders being banned.

[Kev Martin]

I would never brush a dry mix in to point up a patio. Always a wet mix. Brushing in is likely to create its own problems. Particularly when laying a sandstone patio as the gaps between the slabs are much bigger than regular sized slabs.

I find it odd you say this issue has occurred because a DPM wasn’t used. Show me a patio with a DPM, I’ve never seen one in the 11 years I was a landscape foreman, whether the patio was laid by a novice or an experienced landscaper. I think these kinds of beliefs profligate in the same waythat window cleaner folklore encourages ridiculous statements about ladders being banned.

I am happy to discuss anything  with you regarding floors, flooring, tiles, tiling, slabs,  Patios, concrete, grout, grout joints,  BS, DDA, regs anything you like.  However, what I won’t is get into a debate with you on what you did, do or believe.  I have  personally tiled 100’s of floors and laid god knows how many patios.  As a company we have supervised many more.  Additionally we have restored 100’s of patios and floors both exterior and interior laid by builders and so called specialists.  90 % of all patios laid, the grout joints, were grouted with a dry mixture brushed in.  The other 10% were epoxy based grouts or fillers.  The width of the joint has no bearing on strength or longevity as long as BS minimums are met in that the grout joint is a minimum of 2mm on walls and 3mm on floors., there is no maximum that we are aware of.  We have never been called back to a floor or patio we have laid or overseen being laid, neither have we ever had a single problem with efflorescence, blooming or sealing any floor regardless of whether it was inside, outside, a driveway, block paving, tiled or slabs.  We have also advised on some fairly large projects undertaken by other companies that have gone wrong and subsequently written reports used as evidence in court.  The knowledge we have, teach or advise on is based on first hand experience.  Advice offered on this Forum is written freely with the sole purpose to help others.  We do this from choice and it is all based on first hand experience.  Whether you or anyone else reading it accepts it is their choice.