Readying Old Gunite for Resurfacing: Chipping, Sandblasting, and Bond Coats

Most resurfacing jobs are won or shed long before the new coating goes on. They are made a decision in the messy, noisy, thankless hours of preparation, when you are staring at an old swimming pool covering and determining precisely just how aggressive to be with damaging, sandblasting, and bond coats.

I have actually walked into greater than one yard where a beautiful new Quartz accumulation finish or PebbleTec was flaking within a year, while the owners vowed the service provider had used "the good things." Typically the product was great. The problem lived underneath, in a slick, badly scarified substrate or a hurried bond coat.

If you recognize how old gunite behaves, just how to scarify it correctly, and just how to combine that surface with the appropriate bond system, you stay clear of those failures. You additionally save on your own from tearing back into a pool that must have lasted 15 to 20 years.

This is a deep dive into that preparation job: what you need to review, what to remove, and exactly how to develop a surface area that will really hold a modern-day finish.

Start with the shell, not the finish

Before you think of Hydrazzo, Diamond Brite, subjected stone coating, or any type of various other surface, you need to treat the structure honestly. Old pneumatically used concrete, whether gunite or shotcrete, can tell you a lot if you understand where to look.

I typically begin with 3 inquiries:

Is the swimming pool shell structurally sound?

Are there energetic leakages or pipes issues?

How a lot of the existing plaster system can legitimately stay?

If you do not address those very first, you take the chance of sprucing up a sick pool with an appealing coat.

Structural peace of mind check

Walk the covering gradually. Touch the walls with a hammer, not simply the floor. Pay unique attention to the pool bond light beam, the initial couple of feet below waterline tile, and any type of noticeable fixing locations from previous work.

Long, continuous fractures that mirror the light beam, or that run across the flooring and up the wall in a straight line, normally should have a lot more analysis. You are wanting to set apart in between a typical shrinking split in plaster and something that could be telegraming activity in the concrete.

If you think activity, you usually need a concrete fixing method before resurfacing: stitching the fracture, opening it up, packing with hydraulic cement, or in severe situations an architectural engineer's involvement. Placing a costs coating like PebbleTec or glass mosaic floor tile over a moving covering is a dish for callbacks.

Plumbing and leak assessment

Next action in any kind of significant gunite resurfacing is confirming control. You do not intend to fill up a newly glued pool and find a line failure or skimmer leak.

On professional jobs, I always advise a swimming pool pipes pressure examination, also if the house owners promise the pool has actually "never shed water." Old suction and return lines, maturing skimmer throats, and rusty light niches can shock you. When you are already stripping plaster and subjecting fittings, it is the most economical time to deal with them.

If the test exposes concerns, timetable repair services prior to you concentrate on finishes. Skimmer throat fixing, substitute of weak installations around swimming pool light niches, and addressing any type of noticeable covering penetrations with hydraulic cement and, where ideal, a local waterproofing membrane layer, all occur in the prep phase.

Existing plaster: when to chip, when to feather

Most old concrete pools have at the very least one prior resurface. Sometimes 2 or three. Each layer transforms the strategy.

You normally fulfill among these problems:

• Original plaster only, worn yet primarily intact
• One prior resurface, with some bond failings
• Multiple layers, evident "white line plaster" at steps and tile line

That "white line plaster" is the thin brilliant line you see where old coping stones or waterline ceramic tile were eliminated in the past and plaster was patched limited to them. It is typically weak and improperly keyed to the concrete below. Treat it with suspicion.

A simple policy: if there is any type of sign of plaster delamination, hollow places, or numerous past layers, intend on a much more hostile substratum scarification. Leaving doubtful plaster is just how you inherit someone else's pending failure.

The hammer test and what it informs you

A 2 to 3 pound hammer is your ideal device. Tap the surface area and listen. Solid, well bound plaster offers a high, crisp tone. Peeled locations audio dull, nearly like tapping cardboard over a void.

On a common 500 to 700 square foot swimming pool, it is regular to discover scattered delamination. When it is separated and little, you can often chip those local sections down to sound material and cut clean transitions. When large wall or floor sections sound hollow, you are much better off devoting to a complete chip out.

Homeowners frequently intend to stay clear of the price and mess of full elimination. The issue is, every pocket of weak material you leave is a location where the new coating can later shear off. I have enjoyed immaculate Quartz accumulation surface peel away in pizza-slice areas, flawlessly adhering to the footprint of old, hollow plaster. No one mores than happy when that happens.

Substrate scarification: exactly how aggressive is aggressive enough?

When specialists discuss "substate scarification" for gunite resurfacing, they suggest mechanically roughing up the old surface area sufficient that the new system can bite right into it. No amount of chemical hoax defeats great texture.

There are 3 primary methods made use of on old gunite and shotcrete shells: breaking, sandblasting, and grinding, usually combined with acid etching.

Chipping: the heavy work

Chipping is not elegant, yet it is crucial when plaster delamination or numerous layers are present.

On a full chip out, the objective is to get rid of all existing plaster and reveal solid, sound pneumatically applied concrete all over. The resulting gunite surface area will not be completely consistent. That is great. What issues is that it is strong and rough.

On a partial chip, which prevails when the existing plaster is normally audio however has local failings, the cracking team cuts tidy, square shoulders around bad locations. Do not feather these bent on a razor edge. You want deepness and a mechanical secret, not a thin taper of old material.

There is a judgment telephone call below. Some crews leave a slim, highly bonded "scratch" of old plaster in position, particularly on vertical wall surfaces, and rely on aggressive scarification and a top quality bond layer to wed old to new. Others demand taking every little thing to bare gunite. The appropriate option depends upon the age of the swimming pool, previous chemistry misuse, and your tolerance for risk.

One information that divides excellent prep from bad: careful operate at installations and infiltrations. Around skimmer throats, pool light niches, major drains pipes, and returns, you want best angles and clean concrete, not loosened chips or undercuts. Commonly we will return with hydraulic cement to load around conduits and penetrations, producing a tight pocket before any bond layer goes on.

Sandblasting: opening up the pores

Sandblasting is not a substitute for cracking, yet it is an effective enhance. After plaster removal or heavy scarification, the surface frequently has laitance, old layers, or slimed feeling scale that have to be removed.

Good sandblasting does two things at once. It removes pollutants and it better roughes up the surface, particularly in edges and limited areas where breaking hammers do a poorer work. On many of the longer lasting resurfacing jobs I have seen, sandblasting is the peaceful hero. It infiltrates the shell where devices and grinding pads can not reach.

You need to handle the mess and shield adjacent Travertine coping, bullnose block, or cantilevered coping. Masking and short-lived shields take even more time than the blasting itself, yet you can not just pepper stone and tile and hope no person notices.

Blast until you see consistent, fresh concrete or plaster profile without any shiny spots. That sheen usually shows continuing to be laitance or scale, and it is precisely what bond layers do not like.

Grinding and acid etching

Rotary mills with ruby cups have their place. They are outstanding for high spots, feathering sides where old and brand-new plaster will certainly meet, and tidying up the pool bond beam just below the waterline floor tile band.

Acid etching, generally with diluted muriatic acid, is not a cure all. Think about a muriatic acid wash as a method to remove fine cement laitance, mineral range, and oils, not as a main prep work step. It must not be the only thing you do to obtain profile. You want the acid to fizz and bite, after that be counteracted and rinsed thoroughly. Recurring acid left in a porous covering can deteriorate a bond layer or begin rusting rebar where cover is thin.

An usual mistake is to acid wash a slick, unscarified covering, rinse it, and call it prepared. That is not substrate scarification. If you can run your turn over the surface area and it feels like smooth porcelain, you are not prepared for a contemporary plaster, PebbleTec, or Quartz accumulation finish.

Managing the bond beam of light, coping, and waterline tile

The leading 12 inches of a pool wall surface are busy. You have the structural bond light beam, coping rocks or a cantilevered deck, the waterline floor tile and floor tile underlayment, mastic joints like Deck-O-Seal between deck and coping, and often evidence of previous repair work loaded right into that white line plaster zone.

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How you handle this location dictates whether your floor tile stays true, your cement lines remain tight, and your coping appears like it belongs.

Coping: reset or preserve

With Travertine coping, bullnose block, or customized coping stones, you typically can not afford to be reckless. Tearing or hammering also boldy splits stones and bricks that might be difficult to match.

On remodels where coping remains, secure it during breaking and sandblasting, but likewise evaluate it for activity. Loosened rocks or a falling short mortared beam can telegram cracks right into the ceramic tile line. Often it is smarter to suck it up and reset a couple of direct feet of coping so you can repair pool water circulation systems the pool bond beam of light and produce a strong edge.

For older cantilevered coping, which is actually the deck put over the beam with foam developing the overhang, the major factor to consider is the growth joint between deck and ceramic tile. If Deck-O-Seal or various other mastic is hard, shrunken, or missing out on, the deck can bear on the ceramic tile and pop it. Prepare for mastic joint substitute throughout or right after resurfacing so the new floor tile band is protected.

Waterline tile and underlayment

Stripping and resetting waterline tile is where sloppy preparation is most visible. Under the floor tile, you need to see a regular, level ceramic tile underlayment of mortar or compacted render. In many older swimming pools that has been patched consistently, typically with whatever got on the vehicle that day.

Before new waterline floor tile or glass mosaic tile enters, strip that location to seem material. Re-render it right and plumb, considering the planned thickness of the new interior finish. If you are switching over from a slim white plaster to a thicker revealed pebble coating, for example, you might need to readjust the ceramic tile band height so the brand-new coating terminates cleanly.

Waterproofing membrane can be helpful at the waterline in frost prone climates or on specifically porous coverings, however it requires to be suitable with the ceramic tile thinset and plaster system. Slapping on a random membrane that will certainly not bond to cementitious coverings is worse than doing nothing.

Grout shade matching is another subtle information. When you spot isolated ceramic tiles or prolong an action strip with new glass mosaic ceramic tile, you want the cement to blend with the existing band. This is not simply visual. Exceptionally soft or polymer hefty cements can act differently in a continuously damp tile band, causing spotting or staining.

Bond layers: the bridge in between old covering and new finish

Once the covering is structurally sound, scarified, cleansed, and any type of repairs around installations are strong, you get to the heart of resurfacing: the bond coat.

A bond layer is not simply "glue." It is a thoroughly proportioned layer that chemically and mechanically secrets the brand-new indoor coating to the ready substratum. If you skimp on this part, you invite plaster delamination later on, regardless of whether you are using fundamental marcite, Diamond Brite, a Quartz accumulation coating, or costs pebble.

There are 3 wide bond layer strategies you see in the field:

• Neat cement slurry over moistened substrate
• Proprietary polymer changed bond layers from plaster makers
• Two phase systems with a scratch coat and a setting coat

Neat concrete slurries can work, however they provide little forgiveness. Mixes that are as well rich in water, or that are applied to a dirty, unscarified covering, will shear. I hardly ever see simple slurries utilized above end job anymore.

Polymer customized bond layers, especially those from producers that likewise create the indoor finish, have chemistry on their side. When you match a PebbleTec style finish to a suitable bond system, for example, you are utilizing an item developed to chemically get both the shell and the covering. The trick is following their precise water ratios, pot life, and treatment time. Over thick application or duplicated retempering in the pail can create weak layers.

Two phase systems, where a harsh scratch layer goes on very first and a slightly richer setup layer bonds the plaster, appear a lot more on very harsh or greatly fixed shells. The scratch works into all the pits and repairs, the second layer makes a merged, keyed surface.

Regardless of system, surface area prep work right prior to the bond layer issues. The covering needs to be tidy, structurally dry yet surface area damp, and free of puddled water. Any kind of dust from eleventh hour grinding should be blown and rinsed away. You want the bond coat to damp right into the pores of the scarified covering, not drift on a layer of slurry dust.

A useful series that actually works

Here is an area checked series for old gunite resurfacing that integrates every one of these aspects, from very first handshake to prepared for plaster:

Document and test

Photograph existing conditions. Execute a pool pipes stress test. Mark splits, hollow areas, and trouble areas around skimmers and light particular niches. Agree with the proprietor on which things are totally cosmetic and which are non flexible repairs.

Strip, chip, and scarify

Eliminate existing interior coating by cracking to seem material, which might suggest full plaster elimination in older or abused swimming pools. Address white line plaster and previous fixing bands dog-eat-dog. Sandblast to open the pores and tidy continuing to be surface areas, after that grind local highs and transitions.

Repair and information work

Open up structural or dubious cracks, pack with hydraulic concrete, and tie in with any shotcrete fixing where product loss is extreme. Tidy and fixing skimmer throats, return installations, pool light specific niches, and main drains. Consider localized waterproofing membrane around persistent leak areas, following producer guidelines.

Prep the light beam, coping, and ceramic tile band

Maintain or reset loosened coping stones, addressing the pool bond light beam as needed. Get rid of old waterline tile and ceramic tile underlayment to a consistent depth, after that re-render the band to the intended finish density. Prepare for mastic joint substitute with products like Deck-O-Seal after coatings cure.

Clean, etch, and bond

Perform a controlled muriatic acid wash if specified, neutralize thoroughly, and wash to clear water. Allow the covering to drain however maintain it from bone dry problems prior to bonding. Apply the bond coat according to its specification, keeping consistent thickness and preventing puddling or starvation.

Follow this, and you stack the odds strongly in your support. Shortcut any one of those actions, specifically scarification or bond application, and your probabilities swing back towards early failure.

Choosing and matching the new interior finish

Once the covering is straightforward, your option of coating comes to be a blend of aesthetic appeals, feel underfoot, and anticipated solution life.

Traditional smooth white plaster stays the spending plan requirement. It is forgiving to apply, provides an intense blue water shade, however is much more susceptible to hostile water chemistry and etching. When owners insist on white, I press them to devote to tight chemistry control and occasional upkeep like mild acid etching, not radical drain and blast cycles that chew with the surface.

Quartz aggregate coating and subjected pebble surface systems, from business like Ruby Brite and PebbleTec, add solidity and texture. They typically take care of minor chemical misuse far better and hold color longer. They likewise need a slightly more durable substrate profile and bond system, because their mechanical interlock depends on a sound underlayer.

Hydrazzo and other polished accumulation finishes sit someplace between, with a smoother final polish that still has the strength of aggregate however an extra refined feel. These are much less forgiving of bad preparation, especially slim bond coats or uneven substrate account. Any variant beneath telegraphs via a polished surface.

Whatever you pick, match the bond coat and prep strategy to the surface maker's guidance. If the spec calls for a certain substrate scarification deepness, a certain polymer customized bond, or a no acid engrave strategy, presume they have seen enough failings to justify it.

Details that divide strong job from expensive mistakes

By the moment a homeowner is appreciating fresh Glass mosaic floor tile at the waterline, a crisp cement shade matching the coping, and a sparkling new interior coating, they seldom think of what is hidden under the surface area. Specialists do.

Business Name: Adams Pool Solutions
Address: 3675 Old Santa Rita Rd, Pleasanton, CA 94588, United States
Phone: (925)-828-3100

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A couple of less apparent points that come from experience:

Pool light specific niches and skimmer throats are persistent failure areas. Old steel niches can rust at the flange, while skimmer mouths typically break where plastic satisfies concrete. Fixing these with hydraulic concrete, sometimes incorporated with a suitable waterproofing membrane, bores but stops leaks that attack the bond in between shell and brand-new plaster.

Shotcrete repair and patching should be handled with respect for cure times. If you splice in brand-new pneumatically used concrete to repair architectural loss, that patch requires time to treat before it sees a bond layer and new indoor surface. Plastering fresh, wet shotcrete can lead to differential shrinkage and tension at the joint.

Mastic joint substitute is not a cosmetic second thought. When the joint in between coping or deck and floor tile is fired, decks move with heat and cold, after lazy river installation that hammer versus the stiff ceramic tile band. Fresh established waterline floor tile or glass mosaic ceramic tile will certainly not endure that misuse. Effectively applied Deck-O-Seal or comparable products bring back that buffer.

Finally, chemistry and filling procedures after resurfacing belong to the preparation story. You can do book substrate scarification and bond work, after that wreck it by allowing unbalanced fill water, high chlorine shocks, or strong acid enhancements hit a fresh surface area in the very first few days. Education and learning and created startup directions matter.

Gunite resurfacing is unpleasant, loud, and occasionally seems like demolition for its very own benefit. However every piece of old plaster broke off, every square foot very carefully sandblasted, and every appropriately combined bond layer is insurance coverage on your finish.

Prep is where you transform an old, weary shell into a strong base that deserves high end products. If you value that work, the waterline tile stays tight, the Travertine coping looks intentional, the PebbleTec or Quartz accumulation surface stays adhered, and you do not obtain the telephone call two winters months from now about "white lines" and hollow noises. Instead, the swimming pool simply looks right, year after year.