Concrete formwork, shoring, and reshoring field guide

What concrete formwork is, and why it is two systems at once

Concrete formwork is the temporary mold that holds fresh concrete to the shape you want and the support system that carries it there until the concrete can stand on its own. The mold is the part people picture: the plywood face, the panels, the column tube. The support is everything behind it, the studs and walers and ties on a wall, the shores and joists and stringers under a slab. ACI 347 defines formwork as the whole system, mold plus shores plus reshores plus bracing plus hardware, and that definition matters because the failures happen in the support, not the face.

Here is the part that separates formwork from carpentry. Fresh concrete is a heavy liquid. It does not hold its own weight, it does not hold its own shape, and for the first hours of its life it puts its entire load on the formwork. The form is not shaping a solid. It is containing a fluid that weighs about 150 lb per cubic foot and pushes outward on every wall and downward on every shore until it sets.

So formwork is a structural system and a life-safety system in the same breath. When a wall form blows out or a shoring tower buckles, you do not get a cosmetic defect. You get tons of liquid concrete and collapsing lumber coming down on a crew. That is why the trade treats form design like the structural work it is, and why this guide keeps coming back to one fact: the form carries the load until the concrete can, and not one minute before.

Formwork is engineered, not eyeballed

Formwork is a designed structure with a designer, loads, members, and connections, the same as the building it helps build. It is not framed by feel. ACI 347, the guide to formwork for concrete, is the document the trade designs to: it sets the loads the form has to carry, the lateral pressure the fresh concrete develops, and the safety factors on the hardware. A qualified person, often the formwork engineer or the form supplier's engineering group, sizes the members and lays out the ties and shores. The contractor is generally responsible for the means and methods, including formwork safety, but the in-place strength needed before forms or shores come off is specified by the licensed design professional for the project.

The split that gets crews in trouble is this. The form supplier rates the panels, ties, and shores and publishes a safe working load for each. The formwork engineer arranges those rated parts into a system for the actual pour: the tie spacing for the pressure, the shore spacing for the slab load, the bracing for stability. The field crew builds exactly what the drawing shows and changes nothing without going back to the designer.

The drawing is the deliverable. OSHA's concrete and masonry rules, Subpart Q, require that the formwork drawings, including the shoring layout, be available at the jobsite. When an inspector or a competent person walks the form before a pour, the first question is whether what is standing matches what was drawn. If the crew added a foot to the tie spacing or pulled a brace to get a cart through, the form is no longer the form that was designed, and nobody can vouch for it.

The loads a form has to carry

A form carries three kinds of load, and you size the members for all of them together. The dead load is the weight of the concrete itself plus the rebar plus the forms, and normal-weight concrete runs about 150 lb per cubic foot, so a slab's dead load climbs fast with thickness. The live load is the crew, the tools, the buggies, and the impact of concrete landing on the deck. ACI 347 sets a minimum design live load of 50 lb per square foot of horizontal projection, raised to 75 lb per square foot where motorized buggies run, and it sets a floor on the combined dead-plus-live design load of 100 lb per square foot, or 125 lb per square foot with motorized buggies.

Then there are the horizontal loads that try to rack and tip the whole assembly. Wind, the inclined pull of bracing, the lurch of a buggy starting and stopping, the dumping of concrete off-center, the tug of a pump line. The shores and braces have to resist those lateral loads, not just the straight-down weight, because a shoring tower that is strong vertically and weak laterally folds sideways under a push it was never sized for.

The load that has no equal on a vertical form is the lateral pressure of the fresh concrete, and it gets its own section because it is the one that drives the ties and causes the blowouts. Hold the three load types in your head as a set. The deck shores carry the downward dead and live load to ground. The wall ties carry the outward concrete pressure. The bracing carries the horizontal loads that try to push the whole thing over.

How much pressure does fresh concrete put on a form?

Fresh concrete pushes on a vertical form like a liquid, and the deeper the column of wet concrete, the harder it pushes at the bottom. If concrete stayed liquid all the way up, the pressure at the base would be full hydrostatic head, the unit weight times the height, which is why a tall wall poured fast can develop enormous pressure low on the form. The reason real walls survive is that concrete starts to stiffen and set as you place it, so the lower lifts begin carrying themselves before the top is poured, and the actual pressure tops out well below full liquid head on most ordinary pours.

Two field variables decide where it tops out: the rate of placement and the concrete temperature. Pour fast and the whole column stays liquid at once, so the pressure climbs toward full head. Pour into cold concrete and the set is slow, the stiffening that would have relieved the form never arrives in time, and the pressure stays high. Fast and cold is the dangerous combination. Slow and warm is the gentle one. ACI 347 turns that relationship into design equations for walls and columns, driven by the placement rate R and the temperature T.

The equations apply to ordinary mixes, concrete of about 7 in slump or less placed with normal internal vibration to a depth of about 4 ft or less. Outside those bounds, a self-consolidating mix, a deep vibrated lift, a heavy dose of retarder, you do not get to use the reduced pressure and you design closer to full liquid head. And there is a hard floor and a hard ceiling on the result: never design below 600 times the unit-weight coefficient in psf, and never above full liquid head. The full-liquid cap is the honest one. If anything about the pour is uncertain, designing for full hydrostatic pressure is the conservative move that has never blown a form.

Pmax

Maximum lateral pressure of fresh concrete on the form, in psf

R

Rate of placement, the vertical rise of concrete in the form, in ft per hour

T

Temperature of the concrete at placement, in degrees F

Cw

Unit-weight coefficient, 1.0 for normal-weight concrete in the usual density range

Cc

Chemistry coefficient, 1.0 for common cement types without retarders, higher for retarded or heavily blended mixes; verify against ACI 347

w, h

Unit weight of the concrete in pcf and the full height of fresh concrete in the form in ft, which set the full-liquid-head cap

Wall and column forms: studs, walers, and ties

A wall form is a sandwich built to push back against that lateral pressure. The face is the plywood or form panel against the concrete. Behind it run the studs, the vertical members that the face spans across. Behind the studs run the walers, the horizontal members that gather the studs. And tying the two faces together against the outward push are the form ties, which take the whole lateral load in tension and keep the two walls from spreading apart. The load path is face to stud to waler to tie, and the tie is the part holding the wall together.

Spacing follows the pressure, and the pressure is not uniform. It is highest at the bottom of the pour and falls off toward the top, so the ties and studs and walers are spaced tightest near the base and can open up higher on the wall. A column form is the same logic in a tube or a four-sided box, and columns see high pressure because they are poured fast in a small footprint, which is why the column equation in ACI 347 runs straight off the placement rate.

The detail that bites crews is treating the spacing as uniform top to bottom. Space the whole form to the average pressure and the bottom row of ties is under-designed for the real pressure down there, which is exactly where a blowout starts. The form is designed for the pressure at each height. Build it for the pressure at the bottom near the bottom.

Form ties and the blowout

A form tie has a safe working load, a number the manufacturer publishes with a safety factor already built in against its breaking strength. A snap tie, the common light wall tie, might be rated around a few thousand pounds; a coil tie or a she-bolt for heavy forms is rated much higher. You pick the tie for the load and then space the ties so that no single tie ever sees more than its rated safe working load given the pressure at its height on the form. That is the entire design logic, and it is unforgiving in one direction.

Under-space the ties, set them too far apart, and each tie carries more than its share. The pressure does not negotiate. The most loaded tie, almost always one of the bottom row where pressure is highest, reaches its limit and lets go, the load it was carrying dumps onto its neighbors, they overload in turn, and the failure unzips along the wall in a fraction of a second. That is a blowout: the form bursts, the wall spills tons of liquid concrete, and anything in the path of the wall going one way and the concrete going the other is in serious danger.

Blowouts are a pour-rate problem as often as a hardware problem. The ties were sized for a planned rate of placement, the pump got ahead of the crew, the concrete came in faster and colder than planned, the pressure exceeded what the ties were spaced for, and the bottom row failed. The hardware did exactly what it was rated to do. The pour broke the assumption the spacing was based on. Watch the rate, not just the ties.

Slab and deck forms and the shores under them

An elevated slab form is a horizontal deck held up in the air, and everything about it is about getting the downward load to the ground. The concrete sits on the deck sheathing. The sheathing spans to joists. The joists land on stringers, the larger horizontal members. The stringers are carried by shores, the vertical posts or frames that run the load down to a level that can take it, either the ground or a floor below. Load path again: sheathing to joist to stringer to shore to whatever is underneath, and the shore is the member that decides how much slab area each post is responsible for.

Shore capacity and spacing work like tie spacing. Each shore has a rated safe working load, and you space them so the slab's dead-plus-live load per shore stays under that rating. Pack them tighter and each carries less. The deck has to carry the full wet weight of the slab plus the crew and the buggies, which is why ACI 347's 100 to 125 lb per square foot combined-load floor matters most here, on the horizontal form where people and equipment ride during the pour.

The slab form is where the live load is real and moving. A loaded buggy crossing a deck is a rolling concentration of weight the shores have to take wherever it goes. That is the reason ACI 347 raises the live load to 75 lb per square foot when motorized buggies are in use, and the reason a deck that felt solid empty can feel different with three yards of concrete and a buggy on it. Size for the pour day, not the empty deck.

Shoring: getting the load to something that can take it

Shoring is the vertical support that carries a fresh slab's load down to a level strong enough to hold it. The whole game is the load path. A young slab cannot carry itself, so the shores carry it, and they have to land on something that can take the weight without crushing, sinking, or buckling. Land them on a slab-on-grade and the ground takes it. Land them on the floor below in a multistory frame and that floor takes it, which is the start of the reshoring problem covered further down.

Shores come in a few forms. Single post shores, adjustable steel or timber posts, are the simplest and suit lighter decks. Frame shoring and shoring towers, the scaffold-like assemblies, carry heavier loads and stack to reach tall floor-to-floor heights. Flying forms, large pre-assembled deck-and-truss tables, get craned from bay to bay on repetitive high-rise floors. Whatever the type, two things never change: the shore has to be plumb, and the system has to be braced. A shore that leans is carrying an axial load with a sideways component it was not designed for, and a leaning post is a buckling post.

Under every shore is its footing, the mudsill or base. A shore is only as good as what it stands on. A perfectly rated steel post on soft, unprepared ground will punch in, the slab above it will drop, and the load it was carrying will shed to the next shore. The bearing under the shore is part of the shore. Inspect it like one.

What is reshoring, and how is it different from backshoring?

Reshoring is the multistory concept that keeps young floors from getting overloaded by the floors being built on top of them. You cannot leave the original forms and shores in place forever, you need them for the next floor up, so you strip them. But a slab that is only a few days old cannot carry the construction load of the floors above by itself. So as you strip, you put shores back, the reshores, which spread the construction load down across several floors instead of letting any one young slab take it alone. The key detail: a reshore is set snug but does not pick up load until it is placed, and the slab it sits on has already deflected and taken up its own weight before the reshore goes under it. The reshore distributes the new loads from above, not the slab's own dead weight.

Backshoring is the stricter cousin, and the difference is whether the slab is allowed to deflect. Backshores are installed a small area at a time as the original shores come out, so the slab never deflects and never takes up its own weight. The backshore keeps carrying the slab. Where a slab is self-supporting you can use the cheaper reshoring; where it is not, the engineer calls for backshoring, which is more involved because the support is never fully released. ACI 347.2R, the shoring and reshoring guide for multistory buildings, lays out how to tell which one a structure needs.

How many levels of shores and reshores stay in place is an engineered answer, not a habit, because it depends on the slab's strength gain, the construction loads, and how the loads share between floors. Two or three levels is common, but the number comes from the reshoring analysis, and the worst overload often happens not at the new pour but a level or two down, where a young slab is asked to carry more than the finished design ever intended. ACI 318's minimum slab thickness does not account for early-age construction loads, so thickness is no safeguard. The reshoring plan is.

When can you strip formwork?

You strip formwork only after the concrete has reached the strength to carry itself and whatever sits on it, and that strength is set by the licensed design professional in the project specification, not by the calendar. Time is a proxy people reach for and it is the wrong one, because strength gain depends on the mix and the temperature, and a cold week can leave concrete far weaker at three days than the schedule assumed. ACI 347 is plain about the order of operations: supporting forms and shores do not come off beams, slabs, and walls until those members are strong enough to carry their own weight plus any approved load, with no excessive deflection and no cracking when the support is released.

Vertical forms and horizontal forms strip on different clocks. Forms for columns, piers, and walls carry mostly the lateral pressure, which is gone once the concrete sets, so those forms can come off relatively early, often the next day, as long as the concrete can take handling and edge damage. Forms and shores under beams and elevated slabs are a different matter entirely, because they are holding up gravity load that does not go away. ACI 347 recommends removing support from horizontal members only after the concrete reaches about 70 percent of its specified strength, unless the engineer approves otherwise.

Prove the strength, do not guess it. Field-cured cylinders broken to confirm in-place strength, or the maturity method calibrated to the mix, are how you show the concrete is ready before the shores come out. This is where the mix-design and strength discipline ties directly into formwork: the same w/c and the same f'c that the supplier proportioned are what you are now testing to clear the strip. Strip early on a slab that has not made strength and you can crack it, deflect it permanently, or drop it. The cylinder break is cheaper than the repair every time.

Controlling the rate of placement and lift height

The rate of placement is a control you hold in your hand during the pour, and on a wall or column it is the difference between staying under the form pressure and blowing it out. The form was designed for a planned rate, say a vertical rise of 4 or 5 ft per hour. Pour faster than that and the pressure climbs past what the ties were spaced for. The pump operator and the placing crew are, whether they think about it this way or not, holding the form pressure inside its design limit by holding the rate.

Lift height and timing are the levers. Placing a wall in controlled lifts, letting each lift begin to stiffen before the next loads it, lets the lower concrete carry itself and keeps the peak pressure down. Dumping the whole wall in one continuous fast column does the opposite and drives the pressure toward full liquid head. Cold concrete sets slowly, so on a cold day the same rate produces higher pressure, and the safe rate drops. The plan should state the maximum rate of placement, and on a tall or fast pour somebody should be tracking the actual rise against it, not eyeballing it.

There is a cold-joint tension running the other way, and it is real. Pour too slow, or let a lift sit too long before the next one, and the first concrete sets before the next arrives, leaving a cold joint, a plane of weakness where two pours did not knit. So the rate has a window: fast enough to avoid cold joints, slow enough to stay under form pressure. The pour plan picks a rate inside that window for the wall, the mix, and the temperature, and the crew holds it.

What the shores stand on: mudsills and bearing

Shoring on the ground is only as strong as the ground, and the mudsill is what turns a concentrated post load into a pressure the soil can take. A mudsill is the plank, mat, or pad under the shore base that spreads the load over enough area that the bearing pressure stays under what the soil can carry. Skip it or undersize it and the shore punches into the ground, the deck above drops, and the load sheds to the next shores in line, which can start a progressive failure across the tower.

OSHA's Subpart Q puts this in plain language: the sills for shoring shall be sound, rigid, and capable of carrying the maximum intended load. That covers the plank itself and what it sits on. The bearing under the sill is the part crews forget. Soft fill, saturated soil after rain, a sill bridging a buried trench or a soft spot, freeze-thaw heave under winter shoring, and scour where water runs across the bearing all reduce what the ground will hold, and none of them show up if you only look at the shore and not the dirt under it.

Plumb and bearing go together. A shore on a sill that settles unevenly goes out of plumb, and an out-of-plumb shore carries its axial load with a sideways component that invites buckling. Set the sills on prepared, drained, load-tested bearing, keep them level, and check them again after rain and during the pour, because the ground that held this morning may not hold after the water comes.

Bracing and the stability of the shoring tower

A shoring tower can be plenty strong straight down and still fall over sideways, and lateral stability is its own design problem. The vertical members carry the gravity load, but the horizontal loads, wind, the pull of the pump line, a buggy starting and stopping, concrete dumped off-center, all try to rack and tip the assembly. Diagonal bracing is what gives the tower the triangulation to resist those forces and stand instead of fold. A tower without adequate bracing is a stack of posts waiting for a push.

The mindset is the same one that governs tilt-up panel bracing, and it is worth borrowing here. A free-standing element that is only stable because it is braced is exactly as safe as its bracing and no safer, right up until the permanent structure takes over. A shoring tower during a pour is in that condition. The braces are not optional stiffeners. They are part of the load-carrying system, and pulling one to get equipment through, a common and deadly shortcut, removes capacity the engineer counted on.

Brace to the drawing and leave it braced. The diagonals, the lacing between towers, the lateral ties to a stable point are all sized for the horizontal loads the system will see during placement, including the impact and surge of the pour itself. Inspect the bracing as part of the pre-pour walk, confirm nothing was removed, and confirm the connections are made, because a brace that is in place but not bolted is a brace that is not there.

The pre-pour formwork and shoring inspection

The pour is a hold point, and the formwork inspection is the gate. Before any concrete is called, a competent person walks the form and confirms that what is standing matches the formwork drawings, because once the truck shows up the chance to fix anything quietly is gone. OSHA's Subpart Q backs this with timing: shoring equipment is inspected before erection against the formwork drawings, and erected shoring is inspected immediately before, during, and immediately after the placement. The during part matters, because that is when a tie or a sill tells you it is in trouble while there is still time to stop.

The walk has a short list that catches most failures. Are the ties the right type and spacing for the pressure, tight near the bottom where pressure is highest? Are the shores plumb, on sound sills with real bearing, at the spacing the drawing shows? Is the bracing complete, connected, and nothing pulled? Is the form clean, the face oiled, the reinforcement and embeds the inspector signed off in place? And is the planned rate of placement understood by the pump operator and the placing crew, because the form is only safe at the rate it was designed for.

Watch it during the pour and have a stop plan. Somebody should be watching the form for movement, the ties for distress, the sills for settlement, while concrete is going in, and everybody should know that if a tie starts to open or a shore starts to move, the pour stops. A blowout gives a few seconds of warning, a bulge, a creak, a tie singing, and a crew that is watching can clear the line before it lets go. A crew with their backs to it cannot.

Pour sequence and the cold joint

The order and timing of placement is part of the formwork plan, because the form pressure, the cold-joint risk, and the load on the shores all depend on how the pour moves. A cold joint forms where fresh concrete is placed against concrete that has already started to set, so the two do not bond into a continuous member and you are left with a plane of weakness. On a wall, that means placing in lifts and timing them so each lift goes against concrete that is still plastic, not against a surface that has stiffened.

The sequence also manages where the load lands. On a large elevated deck, placing in a planned pattern keeps the shoring from being loaded unevenly and keeps a wet edge moving so successive passes knit. Dumping concrete in one heavy spot piles live load on a few shores and leaves cold joints where the crew falls behind. The plan spreads the placement to match how the form and shores were designed to be loaded.

Where a real construction joint is planned, it gets detailed, located at a low-stress point, and prepared so the next pour bonds, which is a different thing from an accidental cold joint that nobody intended. Plan the joints you want and you avoid the ones you do not.

OSHA Subpart Q and the safety case

Formwork and shoring are governed for safety by OSHA's concrete and masonry construction rules, Subpart Q of 29 CFR 1926, and the section on cast-in-place concrete is the one that controls the formwork, shoring, and reshoring on a jobsite. It is not advisory. It is the enforceable floor, and a formwork failure is exactly the kind of event it exists to prevent.

A few requirements sit at the center of it. Formwork is designed, fabricated, erected, supported, braced, and maintained to carry, without failure, the vertical and lateral loads that could reasonably be applied, and the drawings or plans for the formwork and shoring, including revisions, are available at the jobsite. Shoring equipment is inspected before erection and immediately before, during, and after the pour. Reshoring is erected as the original forms and shores come out wherever the concrete cannot yet carry the load, and reshoring is not removed until the supported concrete has the strength to carry its own weight and everything on it. Forms and shores are not stripped until the structural members can support themselves.

Read those together and the safety logic is the same as the engineering logic. The form carries the load until the concrete can. You prove the concrete can before you remove the support. The drawings on site are how anyone, the foreman, the competent person, the OSHA inspector, checks that the thing standing in front of them is the thing that was designed to take the pour.

Heavy decks and thick mats: data center and industrial forming

The big-pour world, data centers, industrial plants, heavy structures, pushes formwork and shoring harder than ordinary commercial work, and in two directions. The thick mat foundation is the first. A mat several feet deep is an enormous dead load and, while it is being placed, a deep column of fresh concrete that develops high lateral pressure against any edge form and any blockout. These are also mass-concrete pours where the heat of hydration matters, so the placement is slow and staged, which interacts with the form pressure and the cold-joint window at the same time. The mix design and the thermal control plan ride alongside the form design on these.

The elevated decks are the second. Data center floors carry heavy equipment and often run thick, so the slab dead load is high, the shoring is dense and tall, and the reshoring analysis carries more load through more levels than a typical office frame. The construction loads from stacked trades and heavy materials staged on young floors are real and have to be in the reshoring plan, not discovered after the fact.

The lesson from these jobs is that scale removes the margin you get away with on small work. A tie spacing or a shore layout that is forgiving on a thin commercial slab is unforgiving under a deep mat or a heavy industrial deck. On these pours the form design, the placement rate, and the reshoring plan are engineered tightly and followed exactly, because the loads are too large to absorb a mistake.

What to document

The formwork record is what proves the system standing during the pour was the system that was designed, and it is what a reviewer reads after the fact if anything moves. Tie it to the drawing and the rated hardware, and capture it before the pour, not from memory afterward.

For each element, record the form or shore type and the rated safe working load of the ties and shores, the spacing actually built, the design pressure or the planned rate of placement the form was sized for, the bearing and sill condition under the shores, and the in-place strength required to strip along with how it will be proven. Keep the formwork and shoring drawings, including revisions, on site as Subpart Q requires, and note who inspected the form before the pour and that the standing form matched the drawing.

Common mistakes

• Building formwork by feel instead of to an engineered design and the drawings on site.
• Pouring faster than the rate the form was designed for, driving pressure past the tie spacing.
• Under-spacing the ties, especially the bottom row where pressure is highest, and inviting a blowout.
• Spacing ties and shores to the average load instead of the higher load at the bottom of the form.
• Setting shores on soft, undersized, or unprepared bearing so a sill punches in and sheds load.
• Pulling a brace to move equipment through and removing capacity the design counted on.
• Stripping forms or shores before the concrete has proven the strength to carry itself.
• Removing or skipping reshores, or guessing the number of levels instead of following the reshoring plan.

Field checklist

Standards and references

ACI 347, the guide to formwork for concrete, is the design document for the trade. It defines formwork as the whole support system, sets the design loads, gives the lateral pressure equations for walls and columns driven by the rate of placement and concrete temperature, sets the floor and the full-liquid-head cap on that pressure, and recommends the in-place strength for stripping, commonly about 70 percent of specified strength for horizontal members unless the engineer directs otherwise. ACI 347.2R is the companion guide for shoring and reshoring of multistory buildings, where the load-sharing across floors and the reshore-versus-backshore decision live.

ACI 318, the building code requirements for structural concrete, sets the specified strength the structure is designed to, and stripping is tied to a percentage of that strength as the engineer specifies. The licensed design professional sets the strength required to remove forms and shores. ACI 318's minimum slab thicknesses do not account for early-age construction loads, which is why the reshoring analysis, not the slab thickness, is what protects a young floor.

OSHA 29 CFR 1926 Subpart Q, concrete and masonry construction, is the enforceable safety standard, with the cast-in-place requirements governing formwork design, the drawings on site, the shoring inspections, reshoring, and the strength needed before stripping. The form supplier and the formwork engineer publish the safe working loads and the system design that govern the hardware. The exact section numbers and the recommended percentages shift between editions and from job to job, so confirm them against the adopted codes, the current standard editions, and the project specification before you rely on a number on a submittal.

Units, terms, and conversions

Formwork mixes a few unit systems across the design drawings, the manufacturer data, and the field, so the same quantity can read differently from one sheet to the next.

Pressure on a form is in pounds per square foot (psf) in US practice and kilopascals (kPa) in metric, where about 1 kPa is roughly 21 psf. The unit weight of normal concrete is about 150 lb per cubic foot, near 24 kN per cubic meter. Rate of placement is the vertical rise of concrete, in ft per hour or m per hour. Tie and shore capacity is given as a safe working load, the rated load with the safety factor already taken out of the breaking strength. Strength for stripping is a percentage of the specified compressive strength, f'c, proven by cylinder breaks or the maturity method.

Formwork

The whole system that supports fresh concrete: the mold plus shores, reshores, bracing, and hardware

Shore / reshore

A shore carries fresh-slab load to a lower level; a reshore is reset after stripping to spread later construction loads across floors

Backshore

A shore reset a small area at a time so the slab never deflects or takes up its own weight

Form tie

The tension member holding the two faces of a wall form against the lateral concrete pressure

Safe working load (SWL)

The rated load for a tie or shore, the breaking strength reduced by a safety factor

Rate of placement (R)

The vertical rise of fresh concrete in the form per hour, a main driver of form pressure

Blowout

Sudden failure of a wall form when an overloaded tie lets go and the failure unzips along the form

Cold joint

A weak plane where fresh concrete is placed against concrete that has already started to set

Related tools

Calculators and readiness checks for this work

Compare your options

FAQ

People also ask

• What is a concrete mix design?
• How strong does concrete need to be to lift a tilt-up panel?
• What is concrete formwork?
• What is a concrete admixture?
• What is the difference between a mechanical and an adhesive anchor?