How to bid concrete work as a subcontractor

What you are actually bidding

Settle the boundary before you price a yard. On a commercial job the concrete package is split across several MasterFormat sections, and the splits are where money leaks:

• 03 11 00 Concrete Forming and 03 15 00 Concrete Accessories. Forms, bulkheads, keyways, waterstop, dowels, chairs and bolsters, and embed setting.
• 03 20 00 Concrete Reinforcing. Rebar and welded wire reinforcement. Routinely split between furnish and install.
• 03 30 00 Cast-in-Place Concrete. Footings, grade beams, foundation walls, piers, columns, slab on grade, elevated decks, finishing and curing.
• 03 40 00 Precast Concrete. Usually somebody else's package, so say so rather than leaving it unaddressed.

Then draw the line against Division 31 Earthwork, because that is where concrete subs actually lose money. The drawings show a footing at an elevation and a slab sitting on a base course. They do not show who digs, who trims, who compacts, who tests and who hauls the spoils. Decide item by item whether you carry:

• Structural excavation for footings, pits and grade beams, and whether that includes over-excavation to competent soil per the geotechnical report
• Subgrade preparation and compaction testing under the slab
• The granular aggregate base and the vapor barrier under the slab on grade
• Backfill against foundation walls, and compaction of that backfill
• Exterior flatwork: sidewalks, curb and gutter, equipment pads, paving

Those last items sit in Division 32 Exterior Improvements on the civil sheets, and on plenty of jobs the site contractor has them. A concrete proposal that is silent on exterior flatwork will be read as including exterior flatwork.

The third boundary is embeds. Anchor bolts, embed plates and weld plates are commonly furnished under 05 12 00 Structural Steel Framing and set by you. See anchor bolt. Supply and setting are two different scopes, and the tolerance liability travels with the setting, not with the supply.

Read the drawings for your sheets

• S-series structural sheets. Foundation plan, footing schedule, column schedule, wall sections, typical details and the structural general notes.
• Schedules beat plans. The footing schedule governs width and depth by mark. Plan linework is not reliable for either.
• The general notes carry your rebar. Lap splice lengths, hook dimensions, cover, corner bars and bars added at openings live in the words, not the geometry.
• Typical details carry the volume you will otherwise miss. Thickened edges, interior thickenings under masonry partitions, haunches, drop panels, curbs and keyways.
• Architectural sheets. Slab depressions at tile and terrazzo, housekeeping pads, stair pans and the exterior flatwork layout.
• Mechanical, plumbing and electrical sheets. Trench drains, sumps, elevator pits, equipment pads and under-slab conduit. Congested under-slab MEP changes your placing production even when it changes nothing about the volume.
• The anchor bolt plan on the steel sheets, plus the embed details it references.
• The geotechnical report and the specification sections. Mix designs and strengths by element, admixtures, curing method, sealer or hardener, floor flatness and levelness, and who pays for testing. Flatness and levelness numbers are in the spec, never on the drawings, and they decide whether you laser screed with a small crew or hand finish with a large one.

Getting the quantities right

Concrete is bid in three units at once, and they do not scale together:

• Volume in cy. Length by width by thickness, divided by 27.
• Formwork in sfca, square feet of contact area, counting every face that touches concrete, so a wall formed both sides is length by height by two.
• Rebar in tons, taken off in linear feet by bar size, converted to pounds at the ASTM unit weights, then to tons.

Finishing and curing run in sf, edge forms and joints in lf, and accessories by count.

Forming is often the largest single line in a cast-in-place package, ahead of the ready-mix itself. So price the forms, not the yards. Break the form takeoff out by type and by height bracket, and carry your assumed number of reuses as a stated assumption. The same 800 sfca of wall form prices very differently on a job with four repetitive pours than on a job with four different shapes, and reuse is a judgement you make, not a fact the drawings give you.

Tons is the rebar unit, and tons is a poor predictor of placing labour. At the standard unit weights, a ton of #4 bar is roughly 2,990 linear feet and a ton of #9 is roughly 590 linear feet. Same ton, around five times the pieces to handle, place and tie. A congested wall of small bars and a footing mat of large bars should never share a placing rate. Build your rates per ton by bar size and by element from your own crews' history rather than from a published average.

What the obvious volume takeoff misses:

• Over-pour on grade. The drawing assumes a flat subgrade at exact elevation. Real subgrade was trimmed by someone else's machine, and the slab takes whatever the low spots ask for. A 6 in slab on a subgrade averaging a quarter inch low is a 6.25 in slab, over 4 percent more concrete across the entire floor. You pay for that unless your proposal states that subgrade tolerance belongs to whoever trimmed it and that over-pour beyond the specified tolerance is a unit price add.
• Thickened edges and interior thickenings. Take them off in lf, convert to added cy, and keep them as their own line so they survive a scope question.
• Trench bottoms are not neat. Footing volume runs over the scheduled dimensions in real dirt.
• Laps, hooks, dowels and added bars on the reinforcing side, plus accessories.
• Ready-mix charges that are not per yard. Minimum load and short load charges, after-hours delivery, truck standby time, cold weather heating and protection, and pump versus chute versus crane and bucket.

What the GC checks when leveling concrete bids

Bid leveling is the GC normalizing every concrete proposal onto one common scope. Expect them to check:

• The cy, sfca and tons you carried. An outlier gets a phone call, and a quantity you cannot defend loses the job on credibility rather than on price.
• The earthwork line, item by item. Structural excavation, over-excavation, subgrade prep, base, vapor barrier, backfill, spoils removal.
• Rebar furnish versus install, and who details it.
• Embeds and anchor bolts. Who furnishes, who sets, who owns the setting tolerance, and who pays for the fix when a bolt pattern misses.
• Finishing scope. Flatness and levelness, hard trowel versus broom, sealer or hardener, curing method, and whether the curing compound is compatible with the flooring adhesive that arrives months later.
• Joints. Saw cutting and timing, control joint layout, and joint filler. Semi-rigid filler is commonly specified for installation after the slab has done most of its shrinking, which is a return trip long after your crew demobilized. Price the remobilization or exclude it in writing.
• Pumping, winter protection and overtime or weekend pours.
• Exterior flatwork, in or out.
• Unit prices for adds, and any allowances you carried and for what.

Anything you leave silent gets filled in with an assumption, and the assumption will not favour you.

Structure the proposal

A concrete proposal that survives leveling has five parts, in this order:

1. The number, with the cy, sfca and tons it covers and the spec sections it covers.
2. Inclusions, listed as items rather than as a paragraph.
3. Exclusions, listed the same way. This is the most valuable section in the document.
4. Clarifications and assumptions. Subgrade tolerance and who trims, form reuses assumed, mix designs and strengths priced, pump or chute, cold weather protection, crane and site access, pour sizes and sequence, embed supply, testing responsibility.
5. Unit prices for the likely adds: added cy by mix, added sfca by form type, rebar per ton by bar size, added sf of finish, and over-pour per cy.

Price your markup on a cost you can defend line by line, and keep the takeoff that produced the quantities.

Where this fits

When the GC calls to level, the concrete sub who can open the takeoff and show which sheet a quantity came from wins the conversation. If you are running the takeoff itself, Ruh reads the drawing set, measures the scope, and prices the measured quantities against your own price book, with every line traceable back to the sheet it came from, which is exactly what you need when a GC questions your yards.