Why does a patio cover leak at the wall?
A cover is attached to a wall, and the join is where water runs down the wall and under the cover's edge. Flashing and a cap are the defence, and they fail when they lift, are nailed through their face or are not lapped in the right order.
Water from the wall above the cover runs down onto the membrane and must be carried over the join and away from the house. A cap that is nailed through its face lets water run beneath it. A flashing that is lapped the wrong way round sends the water behind the membrane.
The technician checks the order of the layers at the join: the cap over the flashing, the flashing over the membrane and the membrane lapped down over the outer edge. Any reversal of that order is corrected.
What causes ponding on a flat cover?
Ponding is standing water that stays on a flat cover after rain. It comes from a drain set above the lowest point, a sag in the deck or a drain that is blocked, and it stresses the seams of the membrane.
A drain that sits higher than the lowest point of the cover leaves a pool beside it. The water stays until it evaporates, and the membrane above it is under constant load. The seams around the pool are the first to open.
A sag in the deck is harder to correct. The technician measures the fall and records the position of the pool, and the owner is told whether a tapered layer or a re-set of the deck is the right fix.
How are seams and blisters handled on a small membrane?
A seam is cleaned, dried and re-bonded or re-taped along its length. A blister is opened if it is wet, dried and patched with a bonded sheet that overlaps the sound membrane on every side.
Dust and moisture stop a patch from bonding, so the surface is cleaned and dried before the patch goes on. The technician checks the drying with a meter, and the patch is not laid over a damp area.
A blister that is dry on its underside is flattened and sealed. One that is wet is cut out, dried and then patched, since the moisture beneath it will otherwise cause the blister to return.
What does the owner keep for the next season?
The owner keeps a short record of the repairs, the drain checks and the photographs of the ponding areas. The record shows whether the drainage has changed and where the next check should look.
A dated set of photographs of the cover after each season shows whether the pools have grown or the seams have lifted. It is the simplest evidence of maintenance and the first thing a later technician will ask to see.
No warranty is stated on this page. Any manufacturer's terms for the membrane are read and kept with the file.
How are the wall and the covering re-joined after a wall repair?
After a wall repair, the cap and the flashing are re-made and the membrane is re-lapped under them, so the join is sealed in the right order. The new work is tested with water before the wall is closed.
Stucco or siding that has been opened to reach the flashing is closed up only after the test is passed. The technician checks the lapping from the cover side as the joint is sealed, and the water test runs against the wall to show that the join sheds the flow.
The house wall above the cover is checked for staining from earlier leaks. A stain that has dried in the wall is traced to its entry point, since a wall repair that does not find the source will soon show the same mark again.
What about a carport roof attached to a house?
A carport roof that shares a wall or a rafter with the house is read as part of the same junction. Its membrane, drain and flashing are checked together, since a leak at the shared line can show as a stain on the house ceiling some distance from the carport.
The carport is often a lower roof with a short run of membrane and a single drain. Water that reaches its wall junction runs down into the house wall, and the stain can appear in a room that seems far from the carport.
The technician records each junction and its flashing, so the owner knows which line is shared and which belongs to the carport alone. The scope names each.
