How do you check roof sheet fixing claims in Qardho?

A roof sheet fixing claim in Qardho is only worth checking against evidence: a fixing schedule, screw and washer samples, pull-out or torque records, and a walk on a recently fixed roof. Without those, a client is buying a promise about the part of the building that takes the full wind load.

What does roof sheet fixing competency mean on a Qardho roof?

It means the crew can name the fixing, set the spacing and prove the fixing holds in the sheet and purlin actually supplied. Roof sheets are typically fixed with self-drilling screws and sealing washers at crest or pan as the sheet manufacturer and design require. General practice is that the fixings, their spacing and their position are set by the sheet manufacturer and the structural design, and the project specification or engineer should confirm them. A crew that cannot state the screw gauge, length, washer type and spacing for the sheet on site is working from habit rather than a schedule. Ask the supplier for the sheet's fixing guidance and the engineer for the design uplift. Ask the municipal engineer's office whether it holds records for similar roofs in the area.

A credible contractor answers these questions in one conversation:

• Which screw and washer, and why that length for this purlin.
• Spacing at the sheet ends and at intermediate purlins, with the edge zone treated separately.
• How the crew confirms the screw has engaged the purlin and not stripped in the sheet.
• Who inspects and signs off before the next run of sheets goes down.

How do unverified capability claims turn into loose roof coverings?

The gap is between what a bid says and what the crew can do on the day, and it shows up at the fixings. A team that has not fixed this sheet profile before may over-drive screws and crush the washer, under-drive them so the washer never seals, or misjudge purlin position and leave screws spinning in thin sheet. Each of those leaves a sheet that moves under gust load. Wind does not need the whole roof to fail. One run of lifted sheets lets rain in at the laps and the fixings, and the leak then travels along the purlin. The client sees a stain on a ceiling far from the loose sheet. Ask for pull-out or torque test records on the actual purlin and sheet thickness, or agree a small test area and have it checked. Check what the contract says about retesting and defects before work starts.

How do you test the claim before the sheets go on?

Set the evidence requirements in the tender, then verify them at the first bay. Ask each bidder for a fixing schedule, the sheet supplier's guidance, and two recent roofs the same crew fixed. Then do this:

1. Walk one of those roofs with a torch and look at the washer line: crushed, proud or sealed.
2. Ask to see the screws and washers delivered to your site against the schedule.
3. Agree a test bay, fix it, and check screw engagement and washer compression against the specification.
4. Record who inspected, when, and what was corrected.

If a bidder cannot produce records, treat the capability as unverified rather than proven. The decision then sits with the client: test the crew on your site first, or carry the risk.

What to do next

Before awarding, send every bidder the same written request: fixing schedule, screw and washer specification, and two Qardho roofs their crew fixed. Book one site walk with the preferred bidder this week. Ask the municipal engineer's office what roof records it holds for the plot or the street, and put the test bay and its acceptance check into the contract before signatures.