Parapet walls and parapet copings

What a parapet is

A parapet is the part of the external wall that is built up above roof level. On a flat roof it holds the edge of the waterproofing and the thermal insulation, and on the facade it gives the house a straight top edge. It is usually built of masonry or concrete, or, on timber-frame houses, of timber studs clad with boards.

A parapet coping has three jobs: to protect the top of the parapet from water, to shed water from the top clear of the facade, and to cover the top edge of the waterproofing dressed over the parapet.

Section through the detail

1. parapet coping (oplechovanie atiky) falling towards the roof
2. continuous clip (zaťahovací pás) fixed along the full length
3. timber backing board, with a separating layer if required
4. parapet masonry
5. external wall insulation with render
6. roof waterproofing dressed over the top of the parapet, under the metal
7. drip nose held clear of the finished facade

Drawing no.

KV-03

Title

Parapet coping, cross-section

Scale

diagram, dimensions in mm

Revision

14 October 2026

Dimensions and rules

The joints between pieces must allow for expansion. PREFA describes several options, for example a C-shaped sliding joint strip; the method must be decided before work starts.

Substrate and layers

Under the coping there is usually a backing board, which creates the fall and gives the clips something to fix into. PREFA says that a bituminous separating layer on timber evens out small irregularities and protects the timber during the works, and that ventilating the coping should also be considered.

A warning about titanium-zinc: RHEINZINK points out that unprotected bitumen membranes without a mineral finish and some membranes (PVC, ECB) release acidic substances that damage zinc. If water from such a roof runs onto zinc, the manufacturer requires a protective coating or written confirmation of compatibility from the membrane manufacturer.

Material

Parapet copings are most often made from pre-painted galvanised steel in the colour of the windows or facade, pre-painted aluminium or titanium-zinc. In modern architecture with long straight edges, the stiffness of the sheet matters – thin sheet on a wide parapet ripples. Check the combination of metals on the roof with the material comparison.

The most common defects

• a flat top, or one falling outwards – water runs down the facade, leaving streaks and algae on the render,
• a short nose – water gets behind the coping into the insulation,
• sheet screwed down through the top – every screw is a potential hole,
• long pieces with no expansion joints – rippling, torn joints,
• no proper corners – a corner made up from cut pieces and sealant.

Cost

Numiq (updated 14 May 2026) gives €12–35 per m excl. VAT for roof flashing – parapet, ridge – materials not included. The cost of materials depends mainly on the girth: a parapet coping with a 500 mm girth uses half a square metre of sheet per linear metre. The price is also affected by height (scaffolding), the number of corners and whether the backing board is replaced.

The authorities

Under Section 18(5)(a) of Building Act No. 25/2025 Coll., repairing and replacing the surface of a flat roof needs neither a decision on the building plan nor a notification. If you are changing the appearance of the building from public space (for example with a markedly different colour or shape), or the house is a listed monument or in a heritage area, see Flashing – when you need the authorities.

Questions and answers

Which way should a parapet coping fall?

Towards the roof, so that water from the top of the parapet does not run down the facade. PREFA specifies a fall of at least 3° (5.25%); a steeper fall helps stop dirt settling.

How far should the drip nose of a parapet coping project beyond the facade?

PREFA gives 40 mm from the finished wall surface; for surfaces that are not sensitive to moisture, such as ventilated aluminium cladding, 25 mm is enough. According to an expert answer by Coleman quoting it, the Czech standard ČSN 73 3610 specifies a 25 mm drip nose.