Roofs and flat roofs
What is a dry-ridge system, and does it mean the mortar ridge was a defect?
A dry ridge is a mechanical fixing for ridge tiles, with no mortar bed. Mortar bedding is the older method. Mortar that has cracked is a maintenance defect. A dry ridge is an alternative way of holding the tiles, not proof that every mortar ridge has failed, and not something a survey can pass or fail by brand.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Ridge tiles cap the top of a slope. When the mortar goes, wind lifts the tiles. That is worth a rating if the tiles are loose. A dry-ridge kit uses screws and a ventilated strip. It can be a sound repair. It can also be poorly fixed. The surveyor sees whether the tiles are seated, not whether the kit was the right one for the tile. They do not pull tiles up to test the screws.
Do not read “mortar ridge” as an order to buy a dry-ridge system before exchange. RICS does not specify products in the consumer guide. If tiles are loose, ask a roofer what holding method they will use and whether the ridge is ventilated. A price without that scope is a guess. The rest of the slope may not need touching.
What should you ask your surveyor?
- Are the ridge tiles loose, cracked, or only bedded in old mortar?
- Did you see daylight at the ridge from the loft?
- Is any recommendation about the ridge alone?
What are the typical next steps?
- Do not walk the ridge to “check the screws”.
- If you want a quote, ask for the ridge only unless the surveyor has rated the slopes as well.
- Ask whether the ridge needs ventilation, rather than assuming a product name.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Is a mortar ridge illegal now?
No. New work often uses dry fixings. An existing mortar ridge is not unlawful because it is mortar. Loose tiles are the defect.
Does a dry ridge stop condensation?
Some systems ventilate the ridge. The survey has not tested that airflow. A branded ridge is not a condensation calculation.