How to Re-Bed a Loose Ridge Tile Using Mortar Yourself

Re-bedding a loose ridge tile is one of the more achievable roofing DIY tasks for a confident homeowner — provided you can work safely at height and the damage is limited to a small number of tiles. If the mortar has simply cracked or crumbled away and the tile itself is intact, a fresh bed of mortar is usually all that's needed to secure it back in place.

Safety First — Working at Height

Before you touch a tile, take height safety seriously. Falls from roofs are a leading cause of serious injury in New Zealand. WorkSafe NZ recommends that any work at height requires a safe means of access, a stable working platform, and ideally a second person on the ground. At minimum you should:

• Use a roof ladder (one with a ridge hook) to spread your weight and avoid cracking tiles
• Wear non-slip footwear
• Never work on a wet or frosty roof
• Let someone know you're working up there

If your roof pitch is steep (generally above 25°) or you're not comfortable at height, stop here and call a qualified roofer — you'll find local professionals on tradedirectory.co.nz.

Tools and Materials You'll Need

• Cold chisel and club hammer (for removing old mortar)
• Wire brush and stiff brush
• Pointing trowel
• Bucket and mixing paddle or stick
• Safety glasses and gloves
• Roof ladder and extension ladder
• Bagged mortar mix or the ingredients to mix your own (see below)

Choosing the Right Mortar Mix

For re-bedding ridge tiles, a standard 1:3 cement-to-sand mix (one part Portland cement to three parts coarse sand) is the traditional approach. Some tradespeople add a small amount of lime (roughly half a part) to improve workability and reduce cracking — a 1:0.5:4 cement:lime:sand mix is a common variation.

Pre-mixed mortar products are available from Bunnings and Mitre 10 and can be a convenient option for small repairs. Check the packaging to confirm the product is suitable for external, exposed applications.

Avoid using a mix that is too rich in cement — it will be brittle and prone to cracking in New Zealand's variable climate, particularly in areas that experience freeze-thaw cycles (Central Otago, alpine regions) or strong UV exposure.

Step-by-Step: Re-Bedding a Ridge Tile

1. Remove the Loose Tile Carefully

Lift the ridge tile off and set it aside somewhere safe. If it's still partially bonded, use your cold chisel and club hammer to gently break the old mortar bond — work carefully to avoid cracking the tile.

2. Chip Away All Old Mortar

Using the cold chisel, remove all loose and crumbling mortar from both the ridge tile itself and the bedding surface on the roof (the tops of the two courses of tiles on either side of the ridge). Old mortar that is still firmly bonded can be left, but any loose material must go — new mortar won't bond properly to a dusty or crumbling surface.

3. Clean the Surfaces

Brush away all dust and debris with a stiff brush or wire brush. If conditions allow, lightly dampen the surfaces with water — this prevents the dry tile and substrate from drawing moisture out of the fresh mortar too quickly, which weakens the bond.

4. Mix Your Mortar

Mix to a firm but workable consistency — it should hold its shape when squeezed but not be sloppy. Mix only as much as you can use in about 30–45 minutes, especially on a warm or windy day.

5. Apply the Mortar Bed

Using your pointing trowel, apply a generous bed of mortar along both sides of the ridge — typically 25–40 mm deep is appropriate, but follow the profile of the existing bedding. The mortar should fill the gap between the ridge tile and the roof tiles beneath it, providing full support.

6. Set the Ridge Tile

Press the ridge tile firmly down into the mortar bed, aligning it with the adjacent ridge tiles. Tap it gently with the handle of your trowel to seat it. Check alignment by eye along the ridge line.

7. Point the Joints

Use your trowel to neatly finish the mortar at the ends and along the edges of the tile. Smooth it off at a slight angle so water runs away from the joint. Match the style of the existing pointing as closely as possible.

8. Allow to Cure

Keep foot traffic off the ridge and avoid heavy rain on the fresh mortar for at least 24–48 hours. Full strength is reached after around 28 days.

A Note on Flexible Pointing Systems

Many modern roofers now use flexible pointing compounds (sometimes called re-pointing systems or ridge tile adhesives) rather than traditional mortar. These products are more resistant to cracking and movement, which suits New Zealand's seismic activity and temperature swings. Products from Sika are one example. If your existing ridge has been pointed with a flexible system, match like with like.

Does This Need a Building Consent?

Re-bedding a small number of ridge tiles is generally considered like-for-like repair and maintenance and is typically exempt from building consent under Schedule 1 of the Building Act 2004. However, rules can vary — always confirm with your local council if you're unsure. You can find guidance at MBIE Building Performance.

When to Call a Professional

Call a qualified roofer if:

• Multiple ridge tiles are loose or the entire ridge needs re-bedding
• The roof pitch is steep or access is difficult
• You notice cracked or broken tiles, sagging, or signs of water damage in the ceiling below
• You're not confident working at height
• The roof is older and may contain asbestos (common in NZ homes built before the 1990s — do not disturb without professional assessment; see WorkSafe NZ for guidance)

A licensed roofer will also be able to inspect the full ridge line and identify any other issues while they're up there. Find a trusted local roofer on tradedirectory.co.nz.

Sources & Further Reading

• WorkSafe NZ — Working at Height
• MBIE Building Performance — Building Consent Exemptions
• BRANZ — Roof Maintenance Guidance
• Sika NZ — Roofing and Sealing Products
• Bunnings NZ — Mortar and Roofing Supplies
• Mitre 10 NZ — Building and Roofing Materials