If you replace single glazing or old double glazing with HR++ insulating glass, triple glazing or vacuum glazing, you will often have to deal with glazing beads. Glazing beads keep the window in place and, together with sealant, tape and blocks, ensure a neat and sturdy installation. The short rule is simple: You replace glazing beads when they are bad, rotten, damaged or too small for the new glass. With thicker insulating glass, new glazing beads, covering beads or nose slats are often needed.

In this article we explain what glazing beads are, when you need to replace them and what you should pay attention to with insulating glass — per frame material and with a selection aid and checklist.

What are glazing beads?

Glazing beads are narrow wooden, plastic or aluminum profiles that lock the window into the frame. They are placed against the glass and secured in the frame. They are then usually sealed or sealed.

Glazing beads have several functions:

  • they keep the glass in place;
  • they ensure a neat finish;
  • they protect the glass edge;
  • they help with water drainage;
  • they allow replacement of glass;
  • together with the sealant and tape, they provide a seal.

With wooden frames, glazing beads are often visible on the inside or outside. Plastic and aluminum frames often have click or clamp slats that are part of the frame system.

Why are glazing beads important?

Glazing beads may seem like a small part, but they are important for the lifespan of the glass and frame. Bad glazing beads can cause leakage, drafts, wood rot, loose glass, poor sealing, moisture in the rebate, damage to insulating glass and a shorter lifespan of the window.

This is extra important with insulating glass. The edge seal of HR++ glass, triple glass or vacuum glass must remain dry and protected. If water remains at the glass edge, insulating glass can leak more quickly.

Bad or too small glazing beads for thicker glass = replace. Good glazing beads keep the glass edge dry and protected — no wood rot, no leaking glass. If you invest in new glass, make sure that the surrounding components are also in order.

When should you replace glazing beads?

You replace glazing beads when they no longer function properly or do not fit the new glass. Replacement is wise for:

  • wood rot;
  • cracks;
  • loose glazing beads;
  • warped slats;
  • damage during removal;
  • bad old sealant seams;
  • too little space for thicker glass;
  • outdated nose slats;
  • poor water drainage;
  • switch from single glazing to HR++ glazing;
  • renovation of the frame.

If you do have new glass installed, that is often the best time to check or replace the glazing beads.

Image: wooden glazing bead with wood rot and open sealant seam next to a new, painted glazing bead

Glazing beads per glass type

The glass thickness determines whether your old slats still fit. Below is what you need to check for each situation.

Replace single glass with HR++ glass

Single glazing is often only 4 to 6 mm thick. HR++ glass is much thicker, usually around 24 to 28 mm. As a result, the old glazing beads often do not simply fit back in. Check:

  • is the rebate deep enough?
  • is there room left for glazing tape?
  • do the glazing beads still fit?
  • is there enough kit space?
  • can the glazing bead be firmly secured?
  • Does the appearance remain neat?
  • is a cover slat or nose slat necessary?

New glazing slats are often used for old wooden frames, because the old slats are too narrow or damaged. See also replacing single glass: options.

Replace old double glazing

If there is already double glazing in the frame, there is a greater chance that new HR++ windows will fit. However, new glazing beads are sometimes necessary. For example, old double glazing can be thinner than modern HR++ glass. Old glazing beads can also be damaged when removing the window. Therefore check:

  • current glass thickness;
  • new glass thickness;
  • condition of the glazing beads;
  • condition of the kit;
  • space for glazing tape;
  • connection to the frame;
  • drainage on the outside.

In the case of leak double glazing, it is wise to also carefully check the glazing beads and sealant seams. Poor glazing can be a cause of moisture problems. You can read more about this job in replacing double glazing.

Triple glass

Triple glass is much thicker and heavier than HR++ glass. As a result, it usually does not simply fit into existing window frames. Pay extra attention:

  • deep rebate;
  • sturdy glazing beads;
  • sufficient support;
  • weight of the window;
  • screw mounting;
  • gap sealing;
  • frame strength;
  • hinges on rotating windows.

Triple glazing is often difficult to install in existing window frames. When you install new window frames, glazing beads and profiles are immediately made suitable for the correct glass thickness.

Vacuum glass

Vacuum glass is thinner than HR++ glass and triple glass. This often makes it fit better in old window frames. However, it still needs to be placed properly. NB:

  • flat rebate;
  • right support;
  • suitable glazing beads;
  • protection of the glass edge;
  • instructions from the supplier;
  • sufficient sealing;
  • no tension on the glass.

Because vacuum glass is technically different from standard insulating glass, correct installation is extra important. Use glazing beads that match the prescribed installation method.

Nosing slat, covering slat or putty?

What is a nose bar?

A nosing slat is a special glazing bead on the outside of a wooden frame. The slat has a protruding or sloping shape, which allows water to drain away from the window better. Nosing slats are often used for insulating glass in wooden frames. Advantages:

  • better water drainage;
  • less chance of wood rot;
  • better protection of the glass edge;
  • longer lifespan of the frame;
  • neat finish;
  • suitable for renovation to HR++ glass.

Old single glazing often contained simple wooden glazing beads or putty. With modern insulating glass, a nose slat is often a better choice on the outside.

What is a rebated slat?

A top slat is used when the new glass is thicker than the old glass and the existing rebate does not provide sufficient space. The cover slat is placed as an extra profile to neatly enclose and finish the glass. Cover slats are useful for:

  • replacement of single glazing with HR++ glass;
  • rebates that are too shallow;
  • renovation of old wooden frames;
  • situations where glazing beads no longer fit;
  • retention of existing frame.

A cover slat can be technically useful, but sometimes changes the appearance of the frame. You can read more about fitting and measuring in will thicker insulating glass fit in my existing frame?.

Glazing beads or putty?

In old window frames, single glazing is sometimes still stuck with putty. Putty was widely used in the past to seal and secure glass. Modern insulating glass usually uses glazing beads, glazing tape, blocks and glazing sealant. Putty is less suitable for modern insulating glass because:

  • insulating glass is thicker;
  • the edge seal must remain protected;
  • good ventilation and drainage are important;
  • modern sealing performs better;
  • maintenance is easier with glazing beads.

When renovating old glass to HR++ glass, old putty edges are therefore often removed and replaced with a more modern glazing system.

Glazing beads per frame material

Replace wooden glazing beads

In wooden frames, glazing beads are often replaced during glass renovation. Wood can be damaged by moisture, paint problems or age. Look for wood rot, open paint, cracks, warping, loose nails or screws, bad sealant seams, moisture spots and soft spots in the wood.

New wooden glazing beads must be well protected with primer, lacquer and suitable sealant. The end edges in particular are sensitive to moisture and must be treated well.

Replace plastic glazing beads

With plastic frames, glazing beads are often part of the profile. They click or clamp in the frame. This means you cannot just use any slat. Check:

  • which profile type the frame has;
  • which glass thickness is suitable;
  • whether suitable glazing beads are available;
  • whether rubbers are still good;
  • whether the frame is suitable for HR++ or triple glazing;
  • whether the system is still available.

Customization is more difficult with plastic frames than with wood. You are dependent on the existing profile system.

Replace aluminum glazing beads

Aluminum frames also have system-related glazing beads. The options depend on the profile and the maximum glass thickness. Pay attention to the glazing bead profile, rubbers, thermal break, condensation risk, maximum glass thickness, condition of the aluminum and the connection with insulating glass.

With old aluminum frames, the frame itself can be a cold bridge. New insulating glass may help, but the frame may still feel cold.

How do you recognize bad glazing beads?

You can often recognize bad glazing beads by visible damage. Signs are soft spots in wood, peeling paint, black spots, cracks, open sealant edges, loose slats, rusty nails, moisture behind the slat, warped wood, leakage on the inside and condensation or dirt near the glass edge.

Do you see these kinds of problems? Then check not only the glazing bar, but also the rebate and the frame wood behind it.

What happens if you leave bad glazing beads in place?

Bad glazing beads can shorten the lifespan of new glass. This is a shame, especially with insulating glass. Possible consequences:

  • water remains at the glass edge;
  • sealant releases faster;
  • frame starts to rot;
  • insulating glass can leak more quickly;
  • drafts and moisture problems arise;
  • window is not secure enough;
  • painting deteriorates faster.

If you invest in new HR++ glass or vacuum glass, you want the surrounding parts to be good as well. Otherwise you are only solving part of the problem.

How are glazing beads replaced?

With wooden frames, replacement usually takes place in steps:

  1. Remove old sealant.
  2. Carefully remove old glazing beads.
  3. Remove window if necessary.
  4. Clean the rebate.
  5. Repair wood rot or damage.
  6. Install new glazing tape.
  7. Install or reset glass.
  8. Cut new glazing beads to size.
  9. Attach glazing beads.
  10. Seal with glazing sealant.
  11. Repair paintwork.

With new insulating glass, this usually happens immediately during installation. Glazing beads, glazing tape and sealant can be found in our glass articles.

Which sealant do you use for glazing beads?

For glazing beads, use suitable glazing sealant. It must be suitable for glass, frame material and outdoor use. Glazing sealant must remain elastic, adhere to glass and wood, be suitable for insulating glass, be weather-resistant, UV-resistant and be paintable if necessary.

Do not use acrylic sealant on the outside. It is not suitable for long-term moisture exposure. Don't just use silicone sealant if the paintwork needs to be touched up later. Are you in doubt? Read which kit do you use for what?.

Do glazing beads need to be painted?

Wooden glazing beads must be well painted. This protects the wood against moisture and extends its lifespan. Important:

  • treat end edges;
  • use suitable primer;
  • finish neatly all around;
  • only paint when the sealant is suitable for painting over;
  • check sealant seams regularly;
  • avoid open seams.

Untreated wood with glazing beads is asking for moisture problems, especially on the outside.

Glazing beads and ventilation of the frame

With insulating glass it is important that moisture does not become trapped in the rebate. That is why the glazing must be constructed properly, with the right blocks, tape, sealant and sometimes drainage. Water drainage is especially important for wooden window frames on the outside. NB:

  • water must be able to drain;
  • glass must not be in moisture;
  • sealant seams must be closed;
  • nose slats can drain water better;
  • frame wood must be protected.

Poor ventilation or drainage around glass can lead to wood rot or leaking insulating glass. Do you also want to solve ventilation through the glass? View our ventilation grilles or read ventilation grille in glass.

Can you replace glazing beads yourself?

With simple wooden glazing beads, a handy handyman can sometimes do this himself. However, caution is necessary, especially with insulating glass. Risks of doing it yourself: glass breaks, window comes under tension, incorrect sealant, poor sealing, insufficient support, damage to the glass edge, moisture problems and no warranty on installation.

For new insulating glass, professional installation is usually more sensible. Especially if you want to apply for a subsidy or have large windows.

Common mistakes when replacing glazing beads

  1. Leave old rotten glazing beads in place — new windows deserve good glazing beads; rotten wood causes new problems.
  2. HR++ Install glass without rebate check — thicker glass does not always fit with the old slats.
  3. Using the wrong sealant — use appropriate glazing sealant, not exterior acrylic sealant.
  4. Do not paint end edges — untreated end edges absorb moisture quickly.
  5. Do not use a nose slat where it is better — a nose slat can improve the lifespan of wooden frames.
  6. Placing glazing beads too tight against glass — glass should be well supported, but not under tension.
  7. Forgot about water drainage — stagnant water near insulating glass can cause problems.

Selection aid: when to replace glazing beads?

Situation Replacing glazing beads?
Glazing beads are rotten Yes
Sealants are bad Often yes
Single glass becomes HR++ glass Often necessary
Old double glazing becomes HR++ glass Sometimes
Frame being painted Check immediately
Glazing beads damaged when removed Yes
New glass thickness does not fit Yes
Outside slat drains water poorly Consider nose bar
Plastic profile has matching slats Only if necessary
Vacuum glass in old frame Depending on prescription

Checklist before replacing glazing beads

  • Are the glazing beads still hard and straight?
  • Is there wood rot?
  • Are the sealant seams open or torn?
  • Does the glass become thicker than before?
  • Does the new glass thickness fit in the rebate?
  • Are top slats or nose slats necessary?
  • Is the rebate clean and dry?
  • Is there sufficient water drainage?
  • Which glazing sealant is used?
  • Do the glazing beads need to be painted?
  • Have the ends been treated?
  • Is the frame suitable for insulating glass?
  • Is the glass professionally installed?

Conclusion

Glazing beads are an important part of properly installed glazing. They hold the glass in place, provide a finish and protect the glass edge. Good glazing beads are extra important for insulating glass, because moisture at the glass edge can lead to problems such as wood rot or leaking glass.

Replace glazing beads when they are rotten, damaged, bent or too small for the new glass. When replacing single glazing with HR++ glazing, new glazing beads, covering beads or nosing beads are often required. For wooden frames, a nose slat on the outside is often a good choice for better water drainage. So don't just check the glass, but also the parts around it — good glass in bad glazing beads is not a sustainable solution.

Get started? First measure your glass properly, order the insulated glass to size and view the matching glazing beads, glazing tape and kit. Are you unsure about the rabbet? Then read will thicker insulating glass fit in my existing frame?.