In brief
- A parapet leaks where the waterproofing turns up at the base and where the coping sits on top, both of which are small details that busy supervision often leaves unchecked.
- Confirm the upstand height, fixing method and coping joint against the project's drawings and specification before each stage is covered.
- Photograph and sign off each stage before the next trade covers it, because defects show up during rain, not on the day the work is finished.
Contents
Parapet detailing supervision gaps in Qardho show up as damp patches on the ceiling after rain. The parapet is the low wall around a flat or low-slope roof. It fails at three small points: the base of the upstand, the top of the upstand and the joints of the coping. None of those points are hard to build. They are easy to skip when nobody checks before the next layer goes on.
Why does parapet detailing fail at roof edges?
It fails where the waterproofing turns up the wall, because the turn-up is small, slow work that gets covered first. Water entering at a roof edge does not need a hole. It needs a lap that is not sealed, a stop end that is short, or a drip that lets rain run back onto the wall. Once the screed or tiles sit over that detail, nobody can see it, and the first sign is a stain on the ceiling below.
The same applies to the coping on top of the parapet. A coping joint can open with movement or thermal cycling, letting water into the wall core. Rain then tracks down inside the wall and appears far from the roof. Ask the site supervisor for the approved detail drawing and the inspection record for the edge before the surface layer went down. If no record exists, treat the edge as unverified and check it from the roof and from inside the room below.
What should a supervisor check before the coping goes on?
Check the upstand height, the seal at the base and the fixing of every coping unit against the spec, not against habit. General practice is to raise the waterproofing up the inside face of the parapet well above the finished roof level and to fix the top of the upstand with a drip or a capping that throws water clear of the wall. Confirm the required height and the cover to any embedded reinforcement with the project engineer, because the drawings for the job govern, not a general rule.
Then check sequence. The membrane and its turn-up should be complete and inspected before screed, insulation or tiles cover them. The coping should be bedded and jointed so water cannot sit in the joint. On site, the supervisor should walk the roof edge, look at the base of the upstand and photograph the detail before it is covered. A client can ask to see those photographs at handover. Test records for any waterproofing product should come from the supplier or the applicator, not from memory.
How do you catch a miss before handover?
Catch it at the stage inspection, because after handover the cost of opening the roof falls on the client. Walk a recently finished building and look at the same edge detail on a wet day. Note where water stands, where the coping joint is open and where the wall shows a damp line. Those signs are visible without instruments.
On your own job, agree a simple hold point: no surface layer over the edge detail until the supervisor has signed the inspection sheet. Ask who signs, what they check against and where the sheet is filed. If the contractor's method statement does not name a hold point at the parapet, ask for it in writing before the roof starts. The municipal engineer's office can say whether it holds drawings or records for the plot, which helps confirm what was approved.
What to do next
Request the project's parapet detail drawing, list the three inspection points (upstand base, upstand top, coping joint) and agree in writing that each one is photographed and signed before it is covered. Walk the roof edge of a recent building in Qardho after the next rain and compare what you see with the drawing. If the detail cannot be found, ask the engineer to issue one before work continues.
Frequently asked questions
Can I check a parapet without opening the roof?
You can check the coping joints, the upstand height above the finished surface and any damp line on the inside wall. The base of the upstand and the membrane turn-up stay hidden once covered, so only an inspection record or a photograph taken before covering proves that detail.
Who should sign off the parapet detail on a Qardho build?
The project's engineer or nominated supervisor signs against the approved drawing. Confirm in the contract who holds that role and where the inspection sheets are filed, so the record can be produced at handover.
Local reporting: this article is written for building work in Qardho and Puntland. Ground conditions, prices and rules differ between places; confirm the details for your own site.