Flagstone question.

[Rick Arrese 14]

I been asked to clean only, not brighten or seal aprox. 2800-3000 sqft of flagstone consisting of walkways, pool apron, pool patio, steps up to another patio then 2 flights of stairs leading to another flagsone deck. Main problem is heavy black mildew in areas covered with shade and near vegetation. There is also English Ivy growing on walls and partially covering the edge of the upper deck 3-5 inches at most. I have a cw 4000psi 4gpm 16hp unit and plenty of hose to get around. I'm concerned a little bit about too much pressure causing some damage. I also have a 20" Cyclone but I don't think it's wise to use on uneven surface like flagstone. My question is should I pre-soak with SH and wash solution first and then rinse or just wash with SH solution and let dry. Also at what pressure range would be safe to operate, if I need to drop PSI can I do that with a 40 degree tip with a larger orifice, 070 maybe? If the HO wants to seal, what would be the best product for this type of surface.Thanks for all your help.

Rick Arrese

Affiliated Svcs. Inc.

Atlanta, GA

[seymore 90]

I've cleaned some Flag stone not much all i used was a S/H/soap mixture sprayed with a shurflo.Let it dwell then rinse. You shouldn't need much pressure.

You might have to wait and see if there are rust spots etc.

I've sealed some with a addement product but i think you can use V-Seal but i'm not sure.The V-Seal rep might chime in on this one.

[MMI Enterprises 289]

Wish we had pictures...

Is it lite color?.. Is it all grouted?.. when they not it sure makes for luvly muddy mess.. If you got any of that white efflorescence situation you may have to go with speciality acid based cleaners and low pressure..may even have to use a sealer to help prevent..

Regardless, to get the black mildew you'll need anywhere from 1 to 6% SH and you may even need hot water or (scary as it may sound) a turbo head on some areas like the ivy if you don't wish to chlorinate it. Set it up with a disclaimer that chlorine could do some the vegitation in even though you'll do your best to prevent it.

Prevent it by not overspraying chems directly of course onto the plants but more importantly do plenty of pre-watering so the plants have their fill and dirt becomes open to absorbtion. Then while doing job and directly after you deep water until you believe the chems have absorbed under the root line of the vegitation. I also tell the customer to water real good over next few days.

I've done this on stepping stone areas and tight flower garden areas and only stuff to ever show any browning or death is that ground cover stuff they sometimes plant between steps...you know it like moss and sometimes has little white baby breath type flowers.

Here's an interesting video link...wanted to run from them myself though:

Efflorescence on Flagstone Can Be Tough To Get Out. Check Out This Free Video!

[Rick Arrese 14]

I will try to get some before pics. The Flagstone is cemented on all butted edges about 1.5" to 2" thick, the mildew in the worst places is carbon black color, no efflorescence noted per se.

[Rick Arrese 14]

Its irregular shaped and several shades of light gray, tan, orange color.

[Scott Paul 164]

It is not advisable to seal flagstone with an acyrlic "wet look" type sealer. The sheen level can be extremely blotchy. If you want to seal it you would want a sealer that would not enhance the color or add a "wet look". I would suggest the SuperSeal-M.

SuperSeal-M Concrete Water Repellent

[MMI Enterprises 289]

Scott,

I understand what your saying and would somewhat agree with the shying away from acrylic if it situation of customer wanting natural look or lower prep costs on a remaintenance.

Have to take issue though with the generalization or imply of no "wet look" on stone though.

When customer wants "wet look" I respect their wants and try to accomodate just like thousands upon thousands of other contractors and manufactures. They have their reasons like easier maintenance and the awesome look in mind.

Although surely there are solvent based acrylics suitable for interior or exterior I go with the 'wet look' lacquers myself.

Here is example found just about any place: Glaze N' Seal (wetlook 2000)

Thing people need to realize is it like anything else and that recoating 1 to 5 year down the road is on the menu and they need to prep it correctly each time.

[sflasealcoatinginc 14]

Wet loook means different things to people..... Alot of people think wet look should mean (high gloss) in most casses it does not and i wouldnt usually recommend putting the sealer on thick enough to make it a high gloss anyway. However, you can put acrylic on Flagstone. Though there are many variations of flagstone.. Sprayed and thinned with xylene very lightly applied should work just fine. We install many flagstone patios and its comming to bemore common down here in florida. And ive sealed many And remember this..... though flagstone does have pores its not as porous as concrete of pavers or brick...so even with a water base sealer you may still get a sheen and wet look on something as slick as flagstone or marble.

[MMI Enterprises 289]

With that said I'll stress the importance of slip resistance of a product...they not all equal at all and the coating is what in the end makes the slickness. Measured it is called slip resistance coefficiency and some product have info avalable, some don't. There is no need these days whatsoever to think that if something is shiny that it has to be slick or slippery. Uncoated concrete, stone, vinyl..you name it can be made to have better characteristics for both wet or dry via coatings....scary though is that they can also be made worse with a coating... i.e- I have a Behr product meant for sealing that you would never ever ever want to place at an entryway less you like to hurt people and have lawsuits against you..

[sflasealcoatinginc 14]

With that said I'll stress the importance of slip resistance of a product...they not all equal at all and the coating is what in the end makes the slickness. Measured it is called slip resistance coefficiency and some product have info avalable, some don't. There is no need these days whatsoever to think that if something is shiny that it has to be slick or slippery. Uncoated concrete, stone, vinyl..you name it can be made to have better characteristics for both wet or dry via coatings....scary though is that they can also be made worse with a coating... i.e- I have a Behr product meant for sealing that you would never ever ever want to place at an entryway less you like to hurt people and have lawsuits against you..

I agree.....anytime we do pool decks.... especially marble,travertine, flagstone... we add shark scale....or 60 grit anti slip.....I buy my stuff from specialty products however they do have similar products at home depot/lowes. Its clear crushed glass beads and you add it to the clear seal...creates a sandpaper-like surface

[MMI Enterprises 289]

I agree.....anytime we do pool decks.... especially marble,travertine, flagstone... we add shark scale....or 60 grit anti slip.....I buy my stuff from specialty products however they do have similar products at home depot/lowes. Its clear crushed glass beads and you add it to the clear seal...creates a sandpaper-like surface

HAHA.. coincidence has me talking elsewhere about that same stuff right before you did..too funny man. :)

Off topic but.....for slip resistance they sell them finely ground glass beads at the decorative concrete suppliers. It can go in just about any type sealer. Can be a PITA though if you don't constantly stirr it or try to do two coats with it. Messes with my whole burnishing plan thingy so I discourage

I should be more specific with other reasons why I discourage it's use in general... (This speaks to the small containers of the glass beeds only)

..In some installations such as decorative crete in hair salons the floors become slick in same amount of time as usual when it put in regular acrylic sealer. Situation is that of sprays and loose hair polishing (abrasion) the surface and after but only a month or less it is back to square one on resistance. It really should not be advised for use in the non permenant coatings is my experience and debatable in the permenant as well. If you picture a microscopic 'hill and valley' situation the hills have no choice but to wear down eventually due to the increased traffic posed on them compared to the valleys. After the top points of hills that dig in to shoes are gone then what you end up with is actually less traction due to less contact/friction points of the shoe traffic.

I prove it regularly on both floors with the beeds or without by the act of burnishing (heat melting) the acrylics or urethanes to gain more resistance. Yup it is true, a flatter/smoother surface is actually more slip resistant. When shoes seem to smooth a floor they actually create microscopic scratches that lessen contact/resistance..

With all that said... if it situation like outside around a pool apron there will not be heavy shoe traffic and it will hold up good in a permenant coating. Commercial forget it...harder grit materials are available for such.