Short answer
A marble threshold (also called a door saddle) is a solid strip of stone set across a doorway where tile meets another floor. It covers the joint, bridges small height differences with a bevelled edge, and gives a clean line under a closed door. Marble, engineered stone, quartz and porcelain are all common. It is cut to fit the opening, set in a full bed of mortar so it's supported end to end, and sealed if it's natural stone. Where floors differ by more than a bevel can handle, a metal transition profile is often the better choice.
Look at the doorway of many tiled bathrooms and you'll find a strip of white marble across it. A marble threshold is a small piece, but it does a real job, and a poorly set one is often the first thing in a bathroom to crack. This guide covers what a tile threshold does, the materials and profiles, sizing, how high it should sit, how it's installed, and when a metal profile is the better answer.
What a threshold does
Where two floors meet at a doorway, something has to finish the edge. A threshold does that in one solid piece. It covers the cut edges of the tile and the other floor, so neither is exposed to chipping or catching a toe.
It also handles height differences. A bathroom floor with a membrane, mortar and tile often ends up a little higher than the hallway floor beside it. A threshold with a bevelled edge steps down gently instead of leaving an exposed lip.
It gives a clean line under a closed door. The classic detail is to have the change of floor fall under the door, so that from each room you see one floor, not a sliver of the other.
And in a bathroom, a raised saddle can hold back a small spill or overflow for a moment. That's a bonus, not waterproofing. The tile floor and its membrane do the real work.
You'll hear several names for the same piece: threshold, saddle, door saddle, marble sill. Many suppliers call bathroom versions a bathroom threshold or tile threshold. They all mean a solid strip across a door opening.
Threshold materials: marble and the alternatives
Natural marble
Marble is the classic choice, usually white with grey veining, though grey, beige and black marble thresholds are common too. It looks right with almost any tile, it is solid stone that can be honed or polished, and small chips can be repaired. The downsides come with being natural stone. Marble is porous, so it needs sealing. Acids such as vinegar and many bathroom cleaners etch it. Veins and natural fissures can be weak lines, and a long, narrow piece of stone cracks if it isn't fully supported.
Engineered stone and quartz
Engineered stone and quartz thresholds are made from crushed stone or quartz bound with resin. They are very consistent in colour, dense, and resist stains better than marble, so most don't need sealing. They can cost more, and stock sizes and profiles are more limited. Cultured marble, a cast product with a coated surface, is another lower-cost option; check how its maker says to clean and repair it, because its surface doesn't behave like solid stone.
Porcelain
Some tile collections include matching porcelain thresholds, and a threshold can be cut from a tile. Porcelain is dense, stain-resistant and needs no sealing. It is thinner than most stone saddles, so full support underneath matters even more. On a cut edge, a glazed porcelain shows its body colour, so through-body or colour-body tile looks cleaner. See porcelain vs ceramic tile for the difference.
Solid surface
Solid-surface thresholds are made of the same acrylic-based material as some countertops. They are uniform and can be sanded to remove scratches, but they are softer than stone and scratch more easily.
Metal profiles
Aluminum, stainless steel and brass transition profiles do a similar job in a much thinner line. They handle larger height differences, allow movement between floors, and suit modern interiors and openings with no door. They are a different look from a stone saddle; more on choosing between them below.
Threshold profiles: flat, Hollywood and double bevel
The edge shape of a threshold is chosen to match the floors on either side.
A flat threshold has square or slightly eased edges on both sides. It is used where both floors finish at about the same height.
A single bevel, often called a Hollywood threshold, is flat along one long edge and bevelled down along the other. The flat side meets the tile flush, and the bevel steps down to a lower floor, usually in the hallway.
A double bevel threshold is bevelled on both long edges. It suits a saddle that sits slightly above the floors on both sides, a common case where an older house has floors at slightly different heights.
A ramped or accessible threshold has a longer, gentler slope for a bigger height difference or where a smooth step-over matters, such as for walkers and wheelchairs. U.S. suppliers often sell these as ADA thresholds.
The ends of a threshold, where they show at the door jambs, are usually cut square and hidden under the casing. If an end will be exposed, it can be polished or eased so it doesn't show a raw saw cut.
Sizes: length, width and thickness
Thresholds are sold in standard lengths, widths and thicknesses, and the exact sizes vary by supplier and by material. You buy the length that is at least as long as the opening, then it is cut to fit.
Length runs the full width of the door opening, from jamb to jamb. In most installations, the ends slide under the door casings and into the jamb so there's no visible gap at the ends.
Width is chosen to cover the wall thickness at the doorway. The tile side usually lines up with the face of the wall or the door stop, and the other edge reaches the other floor. The joint with the other floor should land under the door when it is closed, so the width is chosen with the door position in mind. Measure the full depth of the jamb, not just the door, and allow for the trim.
Thickness matters because it sets the height. A thick stone saddle over a thin floor build-up sits proud; a thin saddle over a thick one sits low. Choose the thickness after you know how high the finished tile will be. Cut thresholds on a wet saw with a blade made for stone or porcelain, and protect your eyes and lungs from the dust. Our guide to cutting porcelain tile covers safe cutting.
How high a threshold should sit
The goal is as close to flush as possible on the tile side, and the gentlest possible step on the other. A threshold that stands proud of both floors is a trip edge, especially at night or for someone shuffling in slippers.
Accessibility standards generally allow only a very small vertical edge at a change in floor level, and ask for anything taller to be bevelled or ramped. Even in homes where those standards don't strictly apply, they are a good target. If someone in the house uses a walker or wheelchair, or might in future, plan for the smallest step you can get.
Height is easiest to fix before the tile goes down. The tile, mortar, any membrane and any heated floor system all add height. Sometimes a different membrane, a thinner tile or levelling the floor on the lower side solves it. Sometimes the right answer is a ramped profile instead of a saddle. Our guide to what subfloor tile needs explains the build-up under tile.
Check the door too. A raised floor or threshold reduces the gap under the door, and doors are often trimmed so they swing clear of the saddle and any bath mat. In a bathroom, the gap under the door also helps air move for the exhaust fan, so don't seal it off completely.
How a marble threshold is installed
A threshold can be set at the same time as the tile or after it. Setting it first gives a fixed height to tile to. Setting it last lets it be cut precisely to the finished floors. Either way, the basics are the same.
- Plan the heights of the tile, the threshold and the other floor before anything is set.
- Undercut the casings and jambs with a jamb saw so the threshold slides underneath. It looks far cleaner than scribing stone around the trim and caulking the gaps.
- Cut and dry-fit the threshold to length. Notches around door stops are weak points in stone, so cut them cleanly and make sure they are fully supported.
- Prepare the substrate. It must be flat, solid and clean. Doorways are often where two subfloor sheets or two framing directions meet, so check for movement there.
- Set it in a full mortar bed. Trowel the floor, back-butter the threshold and press it in so the mortar supports it from end to end. Use white mortar under light marble so grey mortar doesn't shadow through.
- Level it with a straightedge across the tile and the threshold, and check it is flat along its length.
- Finish the joints once the mortar has cured, as described below.
- Seal it if it's natural stone.
The biggest mistake is setting a threshold on dabs or a thin, uneven layer of mortar. A hollow spot under a long, narrow piece of stone turns it into a beam, and the first heavy step cracks it.
The joints on either side are treated differently. On the tile side, the joint is usually grouted like any tile joint, or filled with sealant where it doubles as a movement joint at the doorway (see tile movement joints). On the other side, hardwood, vinyl and laminate all need room to expand, so that joint is left soft and filled with a flexible sealant or covered as the flooring maker shows. Never grout or mortar a wood or floating floor tight to the stone.
Why thresholds crack and how they're replaced
Most cracked thresholds come down to support. Hollow spots under the stone, from spot-bonding or poor coverage, leave it spanning a gap. A subfloor that flexes at the doorway, or a joint between two subfloor sheets right under the saddle, adds movement in exactly the wrong place. Notches cut for door stops, natural fissures in the stone, and heavy loads such as an appliance rolled across the doorway finish the job.
A crack across a threshold usually means it should be replaced rather than filled. The grout and sealant around it are cut out, the broken stone is lifted or broken out carefully so the neighbouring tile isn't damaged, the old mortar is scraped off, and a new threshold is set in a full bed. If the cause was movement under the doorway, that is fixed first, or the new one will crack too. Small surface chips on marble can often be filled with a tinted stone epoxy instead; see how to fix chipped tile. Replacing a threshold is a typical tile repair job.
Sealing and caring for a marble threshold
Marble is porous, so a marble saddle is usually sealed with a penetrating stone sealer after installation, and some installers seal it before grouting too, so grout pigment doesn't stain it. Reseal when water stops beading on the surface.
Clean it with a pH-neutral cleaner made for stone. Vinegar, lemon and many bathroom cleaners etch marble and leave dull marks, which is a common sight on bathroom saddles next to the toilet. Our natural stone care guide explains the water test and how to deal with etching and stains.
Threshold or metal transition profile?
A stone threshold is the better choice where there is a door, where you want a classic look, where the doorway is deep enough that the saddle covers the whole jamb, and where the floors are close in height. It also hides small irregularities in the cut edges of both floors.
A metal profile is often the better choice where the height difference is too big for a bevel, where a floating floor needs to move freely, in wide openings with no door, in modern spaces with very thin lines, and in commercial corridors where an edge takes heavy carts. Metal profiles can also be set into the tile as it goes down, which gives a protected, precise edge. Our guides to floor transition strips and tile edge trim compare the profile options.
Shower curbs and stone curb caps
The same solid stone is often used to cap a shower curb. A one-piece cap on top of the curb has no grout joints along its top, which is where water sits and grout wears. The cap usually slopes slightly toward the inside of the shower so water runs back in rather than out onto the bathroom floor.
The curb is waterproofed first, wrapped in the same membrane as the rest of the shower, and the cap is set on top in mortar. A stone cap is never the waterproofing itself. Many bathrooms match the curb cap, the door threshold and a shower window sill in the same stone. If you're planning a curbless or low-curb shower, see our guide to walk-in showers.
Ottawa homes: bathroom tile meeting hardwood or vinyl
The most common threshold in Ottawa homes is between a tiled bathroom and a hallway of hardwood or vinyl plank. Each floor behaves differently. Tile and stone are rigid. Hardwood shrinks in the dry heating season and swells in humid summers, so a joint that looks tight in July can show a gap in February. Our guide to hardwood floors in an Ottawa winter explains why. Floating vinyl and laminate need a clear expansion gap at every edge, including the doorway.
A saddle handles all of this neatly. The tile side is set solid. The other side keeps its gap, finished with a colour-matched sealant or the profile the flooring maker allows. The bevel takes care of the height difference that often appears when a renovated bathroom with a membrane meets an older hallway floor. If you are replacing the hallway floor at the same time, plan the heights together. See our hardwood flooring and vinyl flooring pages for those floors, and how to tile a floor for the tile side.
Frequently asked questions
What is a Hollywood threshold?
A threshold with one flat edge and one bevelled edge. The flat side meets the tile flush, and the bevel steps down to a lower floor on the other side.
What size threshold do I need?
Measure the door opening from jamb to jamb for the length, and the full depth of the wall at the doorway for the width. Buy a stock size at least that long, choose the thickness to suit the finished tile height, and cut it to fit.
Should a marble threshold be grouted or caulked?
On the tile side, it's usually grouted, or sealed where the doorway needs a movement joint. On the side facing hardwood, vinyl or laminate, it should be a flexible sealant, because those floors need room to move.
Does the threshold go in before or after the tile?
Either works. Setting it first gives a fixed height to tile to; setting it last lets it be cut to the finished floors. What matters is a full mortar bed under it.
Do I need a threshold between tile and hardwood?
Not always, but you need something to finish the joint and leave the wood room to move. A stone saddle or a metal transition profile are the usual choices; see floor transition strips.
Why does my marble threshold keep cracking?
Usually because it isn't fully supported, or because the floor flexes at the doorway. A new saddle will crack again unless the substrate is fixed and the stone is set in a full mortar bed.
Do marble thresholds need to be sealed?
Yes. Marble is porous, so seal it after installation and reseal when water stops beading. Engineered stone, quartz and porcelain thresholds usually don't need sealing.
