In brief
- A low mortar bid usually omits sieving, gauging, curing or wastage, not the cement itself.
- Inconsistent bond strength shows up when sand is unmeasured and water is added by eye.
- Ask bidders to price sand, water and curing separately, then match each line to the specification.
Contents
How do mortar mixing underbidding risks in Qardho start?
Answer by price, not by specification, and the cheapest mortar line wins the tender. Mortar is the cheapest visible line in a masonry bill, so a bidder can cut it hard and still look competitive. The saving rarely comes from cement. It comes from what the winning bidder leaves out: sieving sand, measuring by gauge box or bucket, controlling water, covering the mortar board, and curing the finished wall. A bill that says "mortar 1:5" with no route to test it invites each bidder to imagine a different mix. Ask the municipal engineer's office, or read the plot's drawings, to confirm the mix design and sand source the specification expects, then compare every bid against that written description rather than against the lowest number. Check what the contract allows before you reject a line; some bills permit substitution with approval.
Which costs do low mortar bids leave out?
Sieving, gauging and wastage head the list. Sand delivered to a site can carry roots, clay lumps and oversize gravel, so inspect your own sand source and confirm the acceptance criteria against the project's specification before batching. Sieving it through a screen costs labour hours that a lean bid can quietly drop. Gauging needs a box or bucket of known volume for sand and cement, plus a marked container for water. Wastage and rework matter too: mortar mixed too wet cannot be stacked, so it is scraped off and thrown away, and that sand and cement are never recovered. When a client asks two suppliers for written quotes on sand and cement, the quantity gap between a sieved and an unsieved wall becomes visible. Ask each bidder to show the sand volume, the water source, and the curing method as separate lines. A bid that cannot separate them has not priced them.
How does inconsistent bond strength show up?
It shows up at the joints, not in the bag. Unmeasured sand and water added by eye produce mortar that is too rich in one batch and too lean in the next. Lean mortar crumbles under the trowel and grips the block poorly; rich mortar shrinks and cracks. Both leave weak bond at the bed joint, which is where wind and rain load the wall. On site, scrape a hardened joint with a trowel point: mortar that powders away may have too little cement or too much water. Ask for cube or prism test records for the batch, and check the record's date and mix against the wall it claims to represent. Where no records exist, a laboratory can test a core or a sample. Ask the laboratory for its method and rate before you commission anything.
How can a client close the gap?
Close it in the tender, not on site. Write the mix by volume and the sieve size, then ask for a price per cubic metre of finished mortar rather than a lump sum. Add lines for water, curing and making good. During the work, keep a daily mixing record: sand source, number of gauges, water added, and who checked it.
What to do next
Take the current mortar bill to two bidders and ask each to price sand, water, sieving and curing separately in writing. Then walk a recent wall built by each bidder and scrape a hardened joint. Compare what you see against the written mix. If the two do not match, ask the bidder to reconcile them before you sign.
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.