In brief
- A low flashing bid often omits laps, fasteners, sealant or the junction work that keeps wind-driven rain out.
- Ask for a measured take-off of every flashing run, including upstands and penetrations, before comparing totals.
- Confirm material grades, fixing spacing and workmanship tolerances against the project specification and engineer, not the bid.
Contents
A low roof flashing bid in Berbera usually wins by leaving work out, not by working cheaper. Flashing is a small share of the roof package, so estimators price it quickly and drop the laps, fasteners, sealant and junction details. The total looks competitive until wind-driven rain in the area finds the gap. The sections below explain how the gap opens, what it does to the roof, and how a client or supervisor closes it before the contract is signed.
Where does roof flashing underbidding risk Berbera start?
It starts when an estimator prices flashing from the roof area instead of a measured run, then allows a single figure for labour without checking how many junctions the roof actually has.
On a typical roof, flashing covers ridge and hip lines, eaves, verges, valleys, parapet upstands, pipe penetrations, tank stands and expansion joints. Each is a separate length, a separate fixing pattern and often a separate material. An allowance built from roof plan area misses the difference between a simple gable and a roof with six penetrations and two parapet walls.
Material grade is the second gap. Sheet thickness, coating class and fastener type decide how long a flashing lasts. Ask the supplier for written data on the grade quoted, then ask the engineer whether that grade matches the specification. Ask the engineer for the roof details and exposure information relevant to the project, so the coating class and fastener choice follow the actual site. Where the tender lists a generic item such as "flashing, all as required", the bidder controls the scope, and the scope tends to shrink.
What does the saving cost the building?
It shows up as water at the junctions, and water reaches the ceiling before anyone sees it on the roof.
Where a flashing run is short, the sheet does not lap far enough under the tile or sheet above it, or over the sheet below. Where fixings are spaced too far apart, wind lifts the edge and opens the lap. Where the sealant is omitted or the wrong type, the joint opens as the metal moves with heat. Water then tracks along the purlin, stains the ceiling and starts corrosion on the fixings it passes.
How long a fixing lasts depends on the site exposure and the coating class chosen. Confirm the fastener type and coating class against the project specification and the engineer's exposure assessment, and record the answer in the specification. Walk a recent roof with a similar pitch and exposure to see how its junctions have aged.
How do you close the gap before award?
You close it by making the bidder describe the work in measurable terms, then checking that description against the specification.
Ask every bidder for a take-off in running metres for each flashing type: ridge, hip, valley, eaves, verge, upstand, penetration and joint. Ask for the material grade, sheet thickness and coating class, the fastener type and spacing, and the sealant or tape proposed. Give a general practice figure for lap and fixing spacing in the tender documents, mark it as general practice, and require the bidder to confirm it against the project specification and the engineer's detail drawings.
Compare the take-offs, not the totals. A bid that shows fewer running metres than the drawings, or that leaves out penetrations and upstands, is cheaper because it is smaller. Ask that bidder to price the missing lines before you compare. Check what the contract allows on measurement and variations, and keep the priced take-off as a contract document so the scope cannot quietly shrink after award.
What to do next
Take the lowest flashing bid and the engineer's roof layout, and mark every flashing run on the drawing in colour. Count the metres, then compare that count with the bidder's take-off. Write to the bidder with the difference and ask for a priced correction before you sign. Keep that corrected take-off as part of the contract.
Frequently asked questions
What should a roof flashing bid in Berbera include?
It should list running metres for each flashing type, the material grade and thickness, the fastener type and spacing, and the sealant or tape. Penetrations, upstands and expansion joints each need their own line.
Can I reject a low flashing bid for being incomplete?
Check what the tender documents and contract allow first. The normal step is to ask the bidder to price the missing lines and resubmit, so you compare complete bids.
Local reporting: this article is written for building work in Berbera and Somaliland. Ground conditions, prices and rules differ between places; confirm the details for your own site.