How To Repair All Types Of Natural Stone
To repair natural stone you must first identify the type of stone that you have. The most common types of natural stone I encounter are marble, granite, limestone and slate. Besides these, I also repair items made of travertine, sandstone and onyx, but not as often. The repairs below cover damaged worktops, vanity tops, floors, stairs, walls, fireplaces, hearths, tables and ornaments, across all of these stone types.
There are many articles written on how to identify different types of natural stone. Most of them are very well-researched, well written and interesting. Most people in the industry understand them, and some like myself may have studied geology. For the layperson trying to identify their piece of stone, these articles can be confusing, as they offer too much information. What difference will understanding the difference between siliceous and calcareous stones, or igneous and sedimentary rocks, really be to them? Very little, I think.
Table of Contents
How To Identify A Piece Of Natural Stone
There are several choices for the layperson to identify a piece of natural stone. If you have a sample piece of the stone, or a piece of the damaged stone, you can take it along to a local stone masons’ yard. In most cases, they are happy to help you. In addition to this, take some photos of the item or area to show them. If the damaged piece is a floor tile, or from a limestone fireplace, or a chip from a granite countertop, visiting a local company specialising in those products is a good start.
High-quality images of natural stones online have never been better. You can start by looking at the websites of companies that supply natural stone. As before, you can try the websites of fireplace companies, kitchen companies, or tile shops. If you are unable to identify your piece of stone from the images on those websites, you can email them a photo of it and follow it up with a phone call.
A simple online search for natural stone images can also help you identify your stone. A search for green marble, white granite or purple slate will give you hundreds of images. The links within the images will take you to the suppliers.
The Names Of Natural Stones
A word of caution with the names of natural stone. The naming of a particular colour of marble or granite will start with the owner of the original quarry. The wholesalers will then give it another name, normally a variation of the name used by the quarry. Individual suppliers — be they kitchen companies, fireplace companies or tile shops — will most likely then give the stone another variant of the original name. All of these companies do this to protect their source and for marketing purposes.
When identifying your stone, go by what you see. Do not be swayed by the name given to the stone.
Different Types Of Finish
Once you have identified the type of natural stone, next you must consider the finish. For example, marble and granite are both supplied with a polished or matt finish. It is easier to repair a matt finish stone than one with a polished finish — the process and some materials are also slightly different.
A good example of this is repairing a piece of black granite. To repair a piece of honed granite, you would use a black resin filler. Once it has set, sand it down to blend it in with the rest of the stone. To repair polished granite, it is better to use a clear resin and add a black pigment to it. When it has set, remove the excess with a knife blade as opposed to sanding down.
Different Types Of Repair
Depending on the damage, there are different ways to repair natural stone. Where a piece of the stone is missing, the damaged area has to be squared off before knitting in a piece of matching stone (read more on this type of repair). If it is a small chip, a resin repair is best. Deep scratches that cannot be sanded down can be repaired with a water-clear resin. It is also possible to repair cracks with this type of resin, however, it will take 24 hours for the water-clear resin to set.
What To Expect From A Repair
You should first decide what you want from a repair. In the case of damaged stairs or a cracked floor tile, safety will be your first concern. Obtaining a perfect colour match of any natural stone really does depend on the age of the original stone — the older the stone, the more likely the colour will have changed since it was quarried. A striking example of this is in The Louvre, where a section of a Carrera marble carving was repaired hundreds of years later; the stonemason used a piece of marble from the original quarry to achieve the match.
It is possible to achieve near perfection with a resin repair. However, the deciding factors are the size of the damage, the position of the damage in the stone, and finally the lighting in the area.
Examples Of Natural Stone Repairs
Below are several examples of natural stone repairs across worktops, vanity tops, floors, stairs, walls, tables, ornaments, fireplaces and hearths. Each one gives a brief outline of the process and the materials used in the repair. Some examples have a link to a longer article where I think a more detailed breakdown will help you.
Carrera Marble Stairs
The marble entrance stairs to this property in West London had several problems. The nosing of the marble steps and threshold were chipped. There were missing pieces of marble. The chip on the threshold had to be matched with an old and stained piece of marble, and I also had to match the level of yellow staining in the original marble.
Before any works could be done the stairs had to be cleaned. Once the marble was cleaned, a good colour match could be found.
How To Repair Travertine
Here are three examples of how to repair travertine on floors and steps. A large chip repaired with a small piece of travertine, a long crack repaired with a resin filler, and a large hole also repaired with a resin filler. Finally, some advice on filling small holes in travertine.
1. A damaged travertine step — This travertine step was damaged during a delivery to an office building in Central London, a common problem. Travertine comes in many different colours and different shades within each colour. You must first clean the stone as best as you can; once clean you can then match the colour of the travertine, and then try to match the veining.
The damaged part of the travertine is cut away, and a small piece is cut to fit into the space, matching the veining in the travertine step. Repairs like this can be repaired with the same resin adhesive used to fill holes in travertine — the basic buff colour resin is a good match for this piece, with pigments added if needed for a closer colour match.
The excess resin is removed, and finally, to give the repair a nice clean look, the rest of the nosing is sanded back.
2. A cracked travertine floor tile — To repair a crack in travertine, thoroughly clean the stone before you start. The last thing you want is dirty lines on either side of your repair, drawing the eye to a repair that should be invisible.
Most cracks in travertine happen along the vein, which makes them easy to repair and hide. I use a buff coloured resin filler and mix about 3 or 4 batches, each a slightly different shade. Aside from the original buff colour, two further batches are mixed — one with a brown pigment added, the other with white — and sometimes a fourth, varying the amount of pigment, is needed.
Applying the resin: mix each batch separately with the hardener and apply each one intermittently along the crack — this breaks up the colours and looks more natural. Depending on the finish, scrape off the excess with a knife blade if polished, or remove it with a 120-grit abrasive (followed by 220 or 320 for a finer finish) if honed. Silicon carbide is the best abrasive disk for natural stone.
3. A large hole in a travertine floor tile — This cross-cut travertine floor tile was damaged by a carpet fitter. I needed three different shades of filler to match the colours and pattern, using a pigment called Ochre to give the resin a yellowish/brown tint.
I mixed them with the hardener separately, adding each colour intermittently in various shapes to form a pattern. Once set, I sanded them down to blend them in further, then polished the travertine to match the rest of the floor.
Some advice on filling holes in travertine — The process is the same for filling small individual holes, but just one shade will usually do; the larger the hole, the more shades are needed for a natural look. To avoid waste, mix your filler and hardener in very small batches, and to remove the excess, use a scraper with a new knife blade fitted rather than sanding, which can leave light patches on the surrounding floor. For more on repairing chips in a similar way, see my guide on repairing a chipped limestone fireplace shelf.
Botticino Marble Vanity Top
The image below is of a Botticino marble vanity top with two main problems: limescale damage and the use of the wrong cleaning products. Unfortunately, the limescale had eaten into the marble around the taps and the marble was breaking away, with pitting as deep as 4mm in places — for more on this kind of damage, see my guide on how to remove limescale from a marble vanity top.
The surface of the other parts of the vanity top was badly scratched, though not deeply. The use of the wrong cleaning products left the marble looking very dull and flat.
Repairing the damaged area around the taps — the area could not be sanded back, as this would leave a dip where water would collect and limescale would form again.
The area around the taps is cleaned, then the damage is repaired with a resin matched to the colour of the marble. Once the resin had set and hardened, the marble was restored using diamond polishing pads.
To restore the colour and shine, I used a marble polishing compound and finally Lithofin MN Polish.
Black Granite Cladding
The damage to this piece of granite wall cladding was close to the goods entrance of a commercial property — it may have been caused by a vehicle, or it had been vandalised. The client did not want to remove the piece of granite at the time, just wanted a cosmetic repair, and would later match and replace the piece.
I used some suction pads to pull out the granite and straighten it as best as possible. Some wedges were inserted into the joints and under the window sill to help hold the granite in place. There was one large chip to repair in the middle, and some pieces had flaked away. To match the granite colour, I used a transparent resin and added a black pigment to it.
The excess resin could not be sanded off, as this would affect the original polished finish of the granite, so I removed it with a knife blade. Finally, the surface was polished with Lithofin MN Polish.
Carrera Marble Fireplace
This marble fireplace was damaged by contractors during refurbishment works in a North London property. The damage was made worse when the contractors tried to repair it themselves.
The pieces of marble had to be carefully separated, cleaned and repaired. Some pieces were kept together to help when fitting the fireplace back into its original position, and new fixing blocks of marble were made — the original fitters had used pieces of brick and large blobs of adhesive.
The opening of the fireplace was already fixed in place, so the marble had to be fitted around it.
White Marble Chip Repair
This new Arabescato marble fire surround was damaged by contractors while it was being fitted, and they had filled the chip with white grout. White marble is very difficult to match perfectly, so where there is veining in the stone I match the colour and pattern of the veining instead of trying to match the white.
I carefully removed the temporary repair with a new knife blade, cleaned the area with white spirit and a clean white cloth, and gently scraped around the edges of the chip. Any residue of the old filler left behind will show on white marble once it is repaired. I then mixed several shades of grey resin, chose two or three of them, added the hardener and applied small dabs to the chip. Before the resin set, I dragged the colours across the damage with a clean knife blade to recreate the veining. Once the resin had set but was not quite hard, I shaved off the excess with another clean blade.
As this was new marble with a honed finish, I shaved off the excess rather than sanding it, which would have meant blending in a larger area, and the repair did not need polishing. On a polished finish I would apply a very thin film of clear resin over the repair and polish it — see my guide on removing a scratch from marble for more on polishing.
A Marble Ornament
There were 2 challenges when repairing this marble ornament. The damage occurred when it was dropped while being moved within a property in West London. The first challenge was repairing it so the break line in the marble couldn’t be seen; the second was that the client did not want the weathered look of the piece to change.
To repair this piece, I had to mill out the middle of the stone without touching the outer edges. A white resin adhesive was used in the middle, with a water-clear resin on the outer edges. The excess adhesive could not be sanded off, as this would affect the finish, so I removed it just before it had fully set with a knife blade.
Granite Bar Top
This damaged granite bar top in a London casino had to be repaired with resin alone, as the original material could not be found. A challenge with repairing granite using just resin is not only matching the colours and pattern, but also allowing for changing light conditions — granite and resin never look quite the same as the light changes.
The bulk of the repair is a black resin filler, roughly shaped to match the profile of the bar top and left 3mm to 4mm short of the surface.
The second and third layers of resin have the various colours added to match the granite. I used two resins with pigments added, making about three batches of white resin in different shades of brown, layered over the black resin. Once set, the excess was removed flush with the rest of the granite — the white resin with pigments does not shine as much as the granite when polished.
A transparent resin with a very small amount of brown pigment was used to match the vein-like patterns, added between and over the white resin, as the transparent resin shines more.
The resin repair is then shaped and polished to match the profile of the bar — the two different resins, with different shades of brown, will react differently as the light changes.
Onyx Table Repair
This is how I repaired part of an onyx table with a piece of marble and a resin adhesive. The trim around the bottom edge of this table had broken off, with part of it missing. Onyx is very expensive to buy and there are not many suppliers in London, so matching the missing piece exactly would have been very difficult — I decided to repair it instead with a small piece of Arabescato marble, together with a clear resin.
The Arabescato marble is cut from a 10mm thick floor tile, milled down to about 6mm and shaped to match the missing piece. The two saved pieces of onyx trim were fixed in place with resin adhesive, and the piece of marble fixed next to them, set back about 4mm from the surface.
I mixed six batches of clear resin with different levels of green pigment, plus 4 batches with different levels of brown pigment to form a vein — when complete, this vein forms a seam between the repair and the original onyx.
The resin is built up over the marble to match the surrounding onyx, with the brown resins added to match the veining elsewhere on the table.
Once the resin repair is complete, the new piece is sanded down and polished to match the rest of the onyx.
Carrera Marble Bathroom
This little project was not so much a repair — I was needed to dismantle the marble around the toilet and bath without damaging it, so the plumbers could access a faulty macerator pump.
The plumbers suspected the pump was located behind the bath panel. The marble around the top of the bath and the bath panel was carefully removed to reveal the pump, and the plumbers were then able to replace it.
To avoid the same problem in future, we decided to make an access panel for easier servicing next time.
I cut a section from the side panel and refitted it to allow easy access to the pump. A bead of silicone on both sides holds it in place — it would only need to be cut to gain access again in future. A gap at the top of the panel assists with removal and refitting when necessary.
The modified panel, together with the piece of marble around the top of the bath, is fixed back in place, and the bathroom is back in use without the cost of replacing any of the marble.
How To Repair A Natural Stone Hearth
Depending on the damage, natural stone hearths can be repaired with resin if it is a small chip — if you have the damaged piece, it can be fixed back in place with a resin adhesive mixed to match the colour of the stone.
Hearths broken into two or more pieces can be removed and repaired in a workshop, and where a replacement hearth is necessary, it can usually be replaced without affecting other parts of the fireplace — for a method that avoids removing the whole fireplace, see my guide on how to replace a limestone hearth without removing the fireplace.
Chipped edges — this black granite hearth was damaged by an outgoing tenant vacuuming the carpets.
The chips were repaired with a transparent resin filler with a little black pigment added. Once set, the excess was removed with a new knife blade and polished to match the rest of the granite.
This chip on a Crema Marfil marble hearth was caused by carpet fitters. A buff coloured resin with a little white pigment added was used for the repair, with the new carpet protected throughout.
Cracked or broken stone hearths — the damage to this black marble hearth was caused by somebody standing on it. Fortunately it was not fixed in place with adhesive or set into the floor, so it could be removed and repaired in the workshop.
I laid the marble on a flat surface and glued the individual pieces together, strengthening the underside with 3 pieces of granite across the full width. The surface was then sanded and polished to hide the break lines before fitting it back in place.
Scratched and chipped grey slate hearth — this hearth was damaged while chopping wood for the fire, with some minor scratches from general use.
The deep chips were filled with a black resin adhesive. Once set, I sanded off the excess and removed the lighter scratches at the same time, using a 120-grit abrasive followed by 320 grit for a finer honed finish, all done by hand to keep the dust down.
Finally, I cleaned the slate with a damp cloth and sealed it with Lithofin Colour Intensifier.
How To Repair A Chip On A Granite Countertop
One of the most common natural stone repairs I carry out is a chipped edge on a granite countertop. Though these repairs are common, it’s nothing to do with the quality of the granite — it’s usually just bad luck when the worktop is hit on the edge with an object. Something as fragile as a teacup can chip granite if it catches at the wrong angle.
This is how I repair a chipped countertop with an epoxy resin. The damaged granite here is Blue Pearl, chipped while loading or unloading the dishwasher below it.
Clean the damaged area — first I clean the damaged area; if the chip has been there for a few weeks or months there will be some ingrained dirt in it.
The best way to clean out the damaged area is to use a small amount of resin — mix it with the hardener, spread a thin layer over the damage and leave it to set, then just as it sets, use the edge of a knife blade to remove it. Most of the dirt and loose material comes away with the resin, and a final clean with a little white spirit leaves the chip ready for repair.
Transparent epoxy resin — I use a transparent resin for this granite, which is easier to polish once set and the excess removed, and takes a little longer to set, giving me time to adjust the pattern.
4 different colours — next, the resin is mixed with different colour pigments to match the granite — four different colours, starting with a dark blue mix and mixing lighter versions of it. Because of the mottled effect in the granite’s pattern, the colours don’t have to be exact.
Applying the resin — one at a time I add the hardener to the resin, applying the lightest then the darkest mix first. As they set, I use a bradawl tool to poke little holes in the resin and the edge of a knife blade to alter the pattern.
Adding the colours — once the first two colours are set, I remove the excess with a new knife blade, then add the other two colours into the holes poked earlier, adding them intermittently to break up the colours.
Remove excess and polish — finally, once all the resin has set, the excess is shaved off with a knife blade, lubricated with a little white spirit to make it easier. The repair is then sanded with ultra-fine silicon carbide abrasives, which won’t scratch the granite, before the whole countertop is polished with a good quality natural stone polish.
