How to Install Parapet Coping Metal: Cleats, Slope, Joint Covers, Fastening and Wind
Coping caps the top of a parapet and keeps water out of the wall. The cleats, the slope and the joints decide whether it stays on in a storm.
- Professional
- 1 to 3 days depending on parapet length
- Updated
The short answer
Install parapet coping by fastening a continuous cleat to the outside face of the wall, running the roof membrane up and over the top of the parapet, then hooking the coping onto the cleat and fastening the roof side. Slope the coping about 1/4 inch per foot toward the roof, leave a joint gap of about 1/4 to 3/8 inch between lengths, cover each joint with a welded or sealed plate, and follow the wind design.
The top of a parapet wall is one of the most exposed surfaces on a building. Rain lands on it, wind hits it from every direction and snow sits on it. A bare parapet top with a sealant line across it will leak into the wall. Coping is the metal cap that covers the top of the wall, sheds water to the roof side and protects the membrane and wall below.
A good coping job is about the parts you do not see: the continuous cleat that holds the outer edge, the waterproof layer under the cap, the slope toward the roof so water does not run down the face of the building, and the joints that let the metal move. A coping that is fastened tight across its whole width, with no gaps or cleats, tears or rattles off in the first big wind.
This guide covers metal coping on a flat roof parapet. For the membrane details under it, see how to flash TPO walls, curbs and corners and how to flash a parapet in torch-on. For edge metal on roofs without a parapet, see how to install TPO-coated edge metal.
Tools
- Tape measure, level and chalk line
- Drill or impact driver with depth control
- Metal shears and nibbler
- Brake and hand seamer for shop pieces
- Caulking gun
- Hot-air welder if using clad coping
- Marker, spacer blocks for joint gaps
Materials
- Coping metal in the specified profile, often aluminum or galvanized steel, pre-finished or TPO-clad
- Continuous galvanized or stainless cleats
- Joint cover plates or splice plates
- Corner and end pieces
- Fasteners suited to wall and cap material
- Self-adhering underlayment or waterproof membrane for the top of the wall
- Sealant compatible with the membrane and metal
Safety first
- Parapet work means leaning over an edge. Tie off and do not work on a parapet top alone, and keep tools and offcuts from falling to the street or yard.
- Long lengths of coping catch the wind like sails. Carry them with two people, lay them flat and weigh them down before fastening.
- Metal edges are sharp and the top of a parapet is narrow. Wear cut-resistant gloves and secure your footing before setting a length.
Step by Step
Step 1: Check the parapet and the membrane below
The top of the parapet should be flat, solid and wide enough for the coping. Check the blocking or sheathing for rot, loose fasteners and level. A coping can only be as straight as the wall. Fix any dips, since they hold water under the metal.
The roof membrane is run up the inside face of the parapet and either over the top or terminated beneath the coping, as the design shows. Apply a waterproof layer, such as self-adhering underlayment or membrane, over the top of the wall and down both faces a few inches. This is the real waterproofing. The coping is the weather cover that protects it.
Step 2: Choose the profile and plan the layout
Coping profiles include a flat top sloped to one side, a peaked top, and an angled face with a drip edge. The coping must be wider than the wall so the legs hang down past the top of the wall, typically with the face leg extending at least 3 inches below the top of the wall on the outside, and the roof side leg shorter. Follow the manufacturer's detail and any design drawing.
Coping lengths are commonly 10 feet. Plan joint locations so a short piece is not left at a corner. Corners are made with factory or shop corner pieces, and each corner needs its own cover plate or sealed splice.
Step 3: Fasten the continuous cleat on the outside face
The cleat is a long metal strip with an upturned edge, fastened to the wall face so the drip edge of the coping can hook onto it. A continuous cleat is stronger than clips, because it spreads the wind load along the whole length. Fasten it at about 12 inches on centre or as the wind design requires, into solid backing.
Keep the cleat straight and at the same height along the wall, so the coping sits true. Seal the penetrations through the cleat into the wall so water does not follow the fasteners inward. Choose metals that will not react: galvanized steel with galvanized fasteners, stainless with aluminum, and so on.
Step 4: Set the first length with slope to the roof
Water that runs down the outside face of a building stains the cladding, collects dirt and rots the wall. Sloping the coping toward the roof sends the water onto the membrane and into the drains. A typical slope is about 1/4 inch per foot across the coping width, often built into the profile, but confirm the design and the manufacturer's detail.
Start at one end or at a corner, and check that the first length is straight and level along its length. A chalk line on the top of the wall gives a guide for the roof-side leg. Errors in the first length carry through the entire run.
Step 5: Fasten the roof side and leave joint gaps
The roof-side leg is fastened to the top or inside face of the wall through the pre-punched slots, at spacing set by the wind design, often every 12 to 24 inches. Slots let the metal move. Fasteners should sit in a neutral position in the slot and not be over-driven, and stainless or coated screws with neoprene or sealant washers resist leaks. Do not fasten through the top surface of the coping where the design does not call for it.
Metal expands and contracts with temperature, so each joint needs a gap, commonly about 1/4 to 3/8 inch, and a spacer makes it consistent. On a long parapet, a joint with no gap buckles in summer heat. Confirm the gap and maximum run length on the manufacturer's specification.
Step 6: Cover each joint and form the corners
A joint cover is a strip of metal or membrane, often 4 to 6 inches wide, placed under the gap so water that passes the joint is caught and sent to the roof side. Set it in a bead of sealant, fasten it on one side only so it can move, and cover it with the next length. Some systems use a clad cover strip that is welded to clad coping. See how to install TPO-coated edge metal.
Corners are the most exposed points. Use formed corner pieces, seal and cover every seam and make sure water running off one length cannot run into the gap at the next. A corner without a cover plate is one of the most common coping leaks.
Step 7: Seal, inspect and plan for maintenance
Seal the end caps and any places where the coping meets another surface. Sealant is a secondary barrier in this detail, since the joint plate and the slope do the main job, but it needs to be checked every year or two because sun and movement crack it.
Check the coping from the roof and from the ground. Look for lifted edges, loose fasteners, gaps wider than planned and staining on the wall below, which shows water is running down the face. In the Fraser Valley, check after every major wind event, since outflow winds and storm gusts lift poorly secured coping first.
Wind and Coping
Wind creates strong suction at the roof edge and at corners, and coping sits right there. Many coping systems are tested against wind uplift standards for edge metal, and the tested fastening, cleat and metal gauge work as a set. Do not change one without checking the others.
Loose coping does more than fall off. It lets wind in under the membrane at the edge, where the membrane termination is held, and the damage can spread across the roof. A coping that rattles is already telling you something is loose.
Material Notes
- Aluminum: light and corrosion resistant, expands more than steel, and needs separation from dissimilar metals and fresh mortar or concrete.
- Galvanized steel: strong and less expansion, but cut edges rust if not protected.
- Clad metal: steel with a membrane coating that can be welded to the roof membrane, removing one sealant line.
- Fasteners: use the type the manufacturer specifies, because the wrong fastener will corrode and stain the metal.
Common Mistakes
- No slope to the roof side. Water runs down the wall face, stains the cladding and rots the wall.
- No waterproof layer under the coping. The metal is only a cover, and a leak at a joint has nothing behind it to stop water.
- Zero joint gap. Expansion in summer buckles the joint and tears the cover strip.
- Face-fastening through the top. Fasteners through the top of the coping are a leak path unless the detail specifically calls for them.
- Missing or short cleat. Clips without a continuous cleat leave the outer edge free to lift in wind.
- Unsealed corners. Corner joints without cover plates are the first place water gets in.
When to Call a Professional
Coping is an edge detail that is exposed to the strongest wind on the building and is usually at height. It needs metal fabrication, a proper cleat and a waterproof layer underneath, and the wind rating depends on getting those right. It is not a good first project.
Call a roofer if coping is loose or missing, if water is staining the wall below the parapet, if joints have opened, or if the membrane at the parapet has lifted. Wall leaks often start at coping and travel far before they show.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Flat Roofing and Torch On service or the towns we cover.
How to Install Parapet Coping Metal: Questions
What is coping on a parapet wall?
Coping is the metal or masonry cap on top of a parapet wall. It sheds water off the top of the wall, protects the roof membrane and wall structure below, and gives the edge a finished look. Metal coping hooks over a continuous cleat on the outside face and is fastened on the roof side, with joint covers over each gap.
Which way should coping slope?
Toward the roof side, at about 1/4 inch per foot across its width, so water runs onto the membrane and into the drains instead of down the outside face of the building. Water on the face stains cladding and rots the wall. The profile often has the slope built in, but the manufacturer's detail governs.
Why is there a gap between lengths of coping?
Metal expands and contracts with temperature, so lengths are set with a gap, commonly about 1/4 to 3/8 inch, to allow movement without buckling. Each gap is covered by a joint plate or cover strip set in sealant, which catches water and carries it to the roof side while allowing the metal to move.
How do you fasten parapet coping so it does not blow off?
Use a continuous cleat on the outside face, fastened close to the wall every 12 inches or as the wind design requires, and fasten the roof side through slots at the specified spacing. The metal gauge, cleat and fasteners work as a tested set, so do not substitute pieces. Corners need the tightest fastening.
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This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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