Post-Tension Concrete Slab Construction Checklist

Concrete
Post-tension Slab Checklist

copyright 2007 Marshall Hansen

  • Rev. 20081026 (powder puff link)
  • 20080422 This is the most popular page in my blog and I sincerely appreciate all who stop to look. This list is compiled from field notes and observations. I’m adding more comments as I see issues in search inquiries. Also, I will be trying to (re)organize the list sequentially though many issues occur concurrently and many issues apply to any slab pour. The simplest advice I can give to anyone is follow the plans. If you do this the risk belongs to the engineer and architect for the design. Any change from plans must be in writing – RFI or letter from PT engineer
  • this applies primarily to light duty PT, multi-family/residential from GC point of view
  • please add any suggestions or comments in the comment box and I may add them to the list
  • see another construction management checklist: Powder Puff Cleaning Checklist
  • link to this page as I will be updating continually – when you need it you will have my latest edition. https://marshansen.wordpress.com/post-tension-slab-checklist/
  • Scope/contract issues

    • Manpower required to maintain schedule, non-performance will be supplemented
    • Daily reports to site Superintendent from sub foreman – # in crew, work done, comments
    • Daily and on-going clean-up, non-performance will be supplemented
    • 24 hour notices to be one time per condition, failure to act 2nd/subsequent time does not require notice to supplement
    • No tolerance harassment policy – wolf whistles, gestures, ogling, yelling, etc.
    • Sub is experienced in proper methods of PT components installation and storage of tendons
    • Sub will install all materials per manufacturers’ specs or assume responsibility (waterstops, etc)
    • Method of elongation spelled out – how tendon is marked, who observes, who gets copies of lab report, etc
    • Batch mix and slump, flyash max, additives, if any
    • Test cylinder break schedule – 3, 14, 28, extra; 7, 14, 28, extra; etc
    • Notes on PT engineer’s plans are requirements for install (while they may not be specified in scope)
    • English speaking supervisor/foreman on site at all times
    • Sub will be included in pro rata LDs if schedule is not maintained
    • Immediately after pour sub will clean area around pump truck and spoils from trucks going to clean out area if on finished pavement
    • When form and finish crews are different sub-subs main concrete sub will have management on site throughout process start to finish/clean up
    • Inspection, permissions of off-site access for placement of pump truck if site layout will not accommodate pump truck for pour
    • When asking for bids if one subcontractor’s price is substantially lower than the other bids consider the possibility that the take-off is wrong, they have not read the specs/plans or made an error in calculations – probably all three. Be prepared for a request to re-engineer the slab using less concrete. The lowest bid does not always save you money

    Pre-pour

    • Are there any discrepancies between Architectural and Post-Tension Engineer plans? Check all dimensions and features. If so, RFIs must be obtained to proceed, meanwhile,
    • Check site layout for building orientation – is it mirrored or flipped from Architectural drawings?
    • Are pilings required? They should be done by now and that’s another checklist, my friend.
    • Inspection checklist showing required inspections from engineer, architect, client, city, county, parish, municipality, ACOE, state or appropriate enforcement division(s), who calls them in? Copies to GC at site
    • Were lifts built up per soil engineer’s specs? Was sub-grade properly compacted? Did lab perform Proctor field test?
    • Call surveyor to stake envelope and finished floor or other reference elevation/points as needed/desired (elevator pit) verify
    • Envelope placement – four corners and reference other site benchmarks – verify
    • Safety – rebar caps w/metal insert (no poke through), barricades around open excavations and forms, safety rails where necessary, trenches for access to elevator pit, OSHA conforming access. Continuous check
    • Electricity available for form carpenters (temporary power) or do they have generator?
    • Is slab elevation per plans – verify with surveyors stake
    • MEP – other trades rough complete and inspected
    • Verify all sleeves and proper placement for any utilities under slab, check PT engineer’s plans/spec for placement requirements
    • Elevator pit layout – verify
    • Elevator pit may require sleeves for sump pump pipes, etc. Verify size and placement
    • Elevator base may have sump pit – verify location and dimensions. Confirm with plumber’s submittal for sump pump dimensions
    • Is waterproof membrane/Bentonite required under elevator pit base? Coordinate with concrete sub
    • Does elevator base have water stop flange or membrane? Does sub have on site? Does sub have proper iron to make watertight joint on site? Keyways? Do you have mfg installation requirements? verify
    • Trenches proper depth/width
    • Beams and footing proper dimension and shape
    • Are there special footings/thickened beams for stairs, chimneys, steel columns, structural features – where, shape, how deep and wide, rebar, etc.
    • Slab forms proper elevation relative to pad for slab thickness
    • Termite treatment and inspection
    • Vapor retarder properly installed, coverage and material per spec (6, 8, 10 mil etc)
    • Forms checked per Architectural drawings, check details pages
    • Forms properly braced to withstand hydrostatic pressure
    • Are two-sided forms properly braced and tied off – inside and outside?
    • Are steel form systems properly assembled, anchored, braced, w/ strongbacks, etc?
    • Is slab insulation required and on site? Installed properly?
    • Block-outs, recessed areas for tile floors, marble thresholds, ADA showers properly formed
    • Release (plastic, oil, silicone, diesel, etc) on brick ledge forms on flat areas so they can be removed without damaging, chipping , finished slab. Convenient but not required. Spec may have note on release agents accepted
    • Brick ledges continuous around columns and returns verify per plans
    • Slope floor in rooms with floor drains – formed or marked with stake for hand finishing
    • No slope of approach to exceed ADA (per plans or half of entries)
    • Control joint and forms properly set, dowels level/on proper plane and stationary – strip form on proper side
    • Tub box placement, ballast, depth, properly installed – cavity for p-trap chase on proper side
    • Proper size of rebar per plans/spec
    • Post-tension cable anchors installed facing the proper direction – dead and live ends
    • Post-tension cables and rebar properly spaced, chaired and tied per plans and mfg specs
    • Corners, beams, walls and footings properly reinforced with rebar – hairpins per plans, if required
    • Proper tie-in of chairs to post tension cables at intersections and chairs under rebar in beams and footings – this is repeated because it is neglected – look again. If they are not tied to tendons they will get knocked off by finishers during pour
    • Plumber check for obvious damage to risers, etc. from form crew, termite applicator. Check 10 foot head or air re-test per specs
    • Verify batch mix with spec, sub and plant – fly ash, slump, curing compound
    • Plan placement of concrete pump at least one day ahead and ensure access through site to pour. Are any powerlines adjacent to pour? Do you have trenches from electric primaries, civil – storm sewer, sanitary sewer, water, etc and were they compacted properly? Flag off any unstable areas, coordinate with concrete sub
    • Order light tower(s) to be delivered the afternoon before an early morning pour. Verify
    • Verify sub has sufficient crew to properly finish slab in workable time
    • Verify finisher crew arrival time – coordinate with pump truck and plant
    • What is weather forecast? Hot , cold, wet, low humidity??
    • Are power trowels on site?
    • Is curing compound on site, staged near slab? Does sub have operable applicator/sprayer?
    • Have these phone numbers already entered in your cell phone and PDA
      • 911 or local emergency direct number if using out-of-state cell phone (call county they will give you direct number)
      • Concrete sub PM, lab, pump, plumber, concrete sales rep, back-up GC staff, emergencies and extra labor needed
      • Printed directions to hospital
    • plan truck cleanout area if not on site plans. Low cleanout dumpster with liner can be ordered from pump/dumpster/waste company. Plan delivery one day ahead and clearly mark off limits for construction trash until after pours are completed. Do not create mud pit
    • EPA entrance or wash area for truck tires ready to minimize mud, silt carried off-site
    • Pipe risers, drains, in floor receptacles, clean outs capped, plugged or taped to prevent dirt and concrete contamination, tops and covers set at right height relative to finished floor surface – level with finished surface VCT, carpet, slab, etc verify with plumber and electrician
    • Low temperature pours require blankets. Be sure there are enough on site to cover the pour and you have materials (weights) to hold the blankets on the slab.
    • Are there any city noise ordinances restricting construction noise to specific times? Will this affect early morning pours?

    Pour

    • Plumber(s) on duty ready to work – mud boots, pvc saw, cleaner and glue, markers, tub boxes, sand, pvc fittings and pipe, spare clean outs, laser level, etc.
    • Anchors for sill plates per spec (bolts, depth, type, spacing )
    • Anchors properly spaced in shear walls
    • Steel footings or j-bolts for steel column/post placement – with template
    • Call lab for pour inspection (lead time varies per lab), slump and test cylinders, what is required in spec?
    • Record truck number, time of delivery, slump – if too wet/dry, if water added
    • Verify designed batch mix and strength with plant and truck documents, during pour track travel time from plant to site
    • All door thresholds recheck for level
    • No added water unless specifically allowed in batch design with required number of revolutions of mixer reached, verify
    • If primary concrete sub hires sub finisher they must have crew/agreement to clean all spoils, butter around clean out area and pump truck during/after each pour (it may be in the scope but make sure they are there to do it)

    Post pour/finishing

    • No slope or broom on thresholds
    • Broom entries perpendicular to slope not parallel with slope
    • Curing compounds, sealers, hardeners, pump sprayer, misters, etc ready for application per specs, manufacturer’s instructions and plans
    • Observe power trowel operators – are they hitting pipes?
    • When do you pull first pull and when do you pull final pull is based upon plans, engineer plan notes (usually on PT pages) and/or specs. First pull is usually within x days of pour. The lab will break cylinders based upon the schedule you give them and the final pull will occur once a PSI threshold is reached. This number is also in plans/specs. If not call your PM if PM doesn’t know call PT slab engineer.
    • Coordinate, verify elongation process/method and recording with sub and lab before first pull. How is length marked, measured, cylinder break x days after pour, etc.
    • Project manager to verify work by concrete sub is complete via on-site Superintendent before releasing payment – spoils clean up, forms removed, block-out mistakes repaired, damage from trucks to landscaping/existing paving, etc.
    • All subcontractors should be reminded from time to time at weekly on-site meetings no chicken hammers, jack hammers, quickie saws, hammer drills are to be used on the slab without notifying the GC and getting approval before starting work. Depth of work must be confirmed and tendons must be located properly.

    After you discover the plumber, electrician, other sub or architect/engineer omitted a sleeve, conduit, anchor, piling, footing, whatever and now have to break the slab to replace, install, remove, repair, etc – what shall I do?

    • DO NOT attempt to locate tendons by sight using live end and fasteners from dead end for reference. During the pour the finishers can move tendons 6 or more inches up, down, side to side, etc. from placement pre-pour.
    • Call the testing lab and ask them for a tendon locate.
    • The price for the technician and the locating instrument will be less than the cost of replacing a broken tendon and a whole lot less than impaling the elevator sub working in the elevator pit when the plumber cuts a tendon moving a floor drain 60 feet away. (No, this did not happen to me but it is possible and you get the point. Work safe. M)

    Tendon Repair

    Did you attempt to repair plumbing, electrical, sleeves without calling the lab for a locate, find a broken tendon after a sub installed a tub, anchor plate, etc? The slab is over-engineered and depending on the location of the broken tendon a repair may not be required. This is a decision only the PT engineer can make. Prepare an RFI with the location clearly described and marked on a tendon layout diagram from the plans, ask if repair is necessary then send RFI and follow RFI response instructions.

    If repair is required coordinate with repair tech and determine what prep work is needed to complete the job.

    Check revision date for updates. Work safe.
    Marshall

    Responses

    1. Lookoing for a reputable PT slab contractor in AZ. Any suggestions? Please advise. Thanx. EM

    2. Would you be able to recommend a certified Contractor that is able to do work on Guam regarding post tension cables? Thank You.

    3. Interesting information, I am a state of Florida certified gc, If you visit my site and add a comment I will approve it and provide a back link to your site

    4. Currently performed several PT cable repairs at a condo building on the water. Wanted to know what specific testing should be done to the damaged cables, anchors, wedges, etc.??? What is typical required? What exactly should I be looking/asking for from the testing company.

      Also, can you recommend any companies which do this type of testing down in Miami, FL?

      • Hi Lindsay, thanks for reading the checklist and writing.

        The first step is to locate the slab specs part of the construction documents and the Owner, the Home Owners Association office, at the condo may have these. The main goal is to find the PT engineers set of drawings, the shop drawings from the concrete contractor for details on all components of the system (tendons, anchors, who is manufacturer, etc) and the notes/details for the tension pull psi on the tendon(s) which are typically on the stamped plans. If the Owner/HOA doesn’t have/can’t find then you’ll need to track down the Architect or General Contractor who designed and built the building(s), or the concrete sub-contractor, and last resort is local municipality building inspector. A stamped set of plans is required for issuing the building permit and subsequent inspections by county/city and they store these after completion, as you know.

        Many large concrete contractors who specialize in PT slabs have a tensioner and operator. There should be documentation regarding the last time the tensioner was calibrated.

        The basic requirement is for the repaired tendon(s) to function as well as originally designed.

        As far as recommendations for test labs in any city I would recommend calling the largest 2-5 concrete contractors in the area and ask them who they use. The original concrete sub may have been out-of-state.

        The lab will probably ask you when will repairs be completed and by whom and will there be a set of plans or specs at the pull?

        A few observations:
        1) “condo building on the water” could mean multi-story with facade. This might get complicated…;
        2) “condo” = liability, document everything;
        3) Please do not take this personally as I’m not attacking you or your request. When you say “performed several PT cable repairs” I’m thinking past-tense, done. I’m not sure what you meant when you go on to ask how to do it. You may have something as simple as a “pop” an inch under surface of the slab which usually happens right after the pull and might be grouted over or a plumber could have cored through tendons on every floor installing a new riser.

        Ideally, if the concrete sub on the project can be hired they should have all of the documents, info and resources to complete the repair of the tendon(s) turnkey. Also, some companies specialize in PT tendon repair and concrete renovation.

        Good luck, my friend,
        Marshall

        • Thanks Marshall for the speedy and detailed response. I still have a few more questions that I am not too clear on how to proceed.

          The building in question was built with first generation PT system (i.e. no grease or caps are present, the anchor and cable end are fully exposed to the pocket grout). 36 deteriorated cable ends (i.e. anchor, wedges and tail end of PT cable) were removed and replaced. All PT cable ends were kept in tact (one foot length of PT cable with engaged anchor and wedges).

          What should be the next step to attempt to determine the conditions for the balance of the existing PT cables? Typically for this type of scenario, what is the standard testing procedure, if any at all?

          I would like to send specifically the wedges to a lab for testing. Is this relevant at all? Should the wedges be tested to see if they have lost their grip ability?

        • Hi Lindsay, I’m happy to try to help. However, my field PT experience is limited to new construction management multi-family and light commercial with related issues. I understand the process of PT rebuild/restore start to finish but you need analysis, engineering, planning and experience.

          I did a little search and found this site: SPS SPECIALTY CONTRACTING SERVICES

          I have no affiliation in any way, contact or connection with SPS but from the case studies on the site it looks like this is their bailiwick.

          Thanks Lindsay – keep me posted,
          Marshall

    5. I am interested in purchasing a home in the pheonix area it has signs that the post tension slab has failed The house has sunk about 4 inches and cracks 3/8 of an inch thick are visible on slab, damage is concentrated in one are What is the proceedure in fixing this and a rough idea on cost to repair such a thing, they have an engineer report which will be released when an offer is accepted.
      any feedback would be greatly appreciated

      • Wow, Sorry for the delay Peter. I took a vacation from my computer.

        My observations: if an engineer’s report exists I would require release BEFORE an offer is made (full disclosure of known defects); otherwise it sounds like a can of worms. Are there no other houses for sale in all of Phoenix?!

        Hope things worked out,
        Marshall

    6. Dear sir,
      I am working as a Project engineer for the post tensioning works. I need to get all the details of making inspection for installation, stressing and grouting works. I need exactly the specifications.

      Should I able to get this through the e-mail.

      Regards,
      velanna.p

      • Hi Velanna,

        I apologize for the long delay in responding – I took a break from using my computer. I have read many books in the past few months, anyway…

        You need, at least: Architectural, Structural, and Post-tension Engineer’s stamped permit set plans with latest revisions; a copy of all RFI’s (ongoing/current); Project Manual/Specifications book; an approved copy of submittals and shop drawings from PT/concrete subcontractor; PM’s construction schedule; concrete sub info; testing lab contact info; etc.

        With the above construction documents, contacts, the checklist, and numerous other PT information sources you should be able to make a plan of action for inspections/verification of specs and reports.

        I am available as an unlicensed consultant/sub-contractor at $425/day plus travel expenses (from OKC) to make observations, take photographs, prepare detailed reports based upon the construction documents, checklist and my field experience/knowledge.

        A general note about inspections – the construction documents, plans, specs, RFIs, etc, are simply the rules for building this specific project/building. The inspection is based upon these rules. It’s that simple. The rules change from project to project and materials and methods change with subs. You have to be aware of the rules and what is being done on site, take pictures, then write the report.

        It is exciting to see a project begin, evolve and finish.
        Hope this was helpful,
        Marshall

    7. Do post tension (for a post tension slab)cables stretch and loosen in time. This is for a house built in texas, 2010

    8. Hello,
      I have a ceiling slab 60 ft x 30 ft x 9″ thick that does not have propper support under neath, im thinking of running PT cables a cross the 30 foot span, can you tell me approximaterlly how tight between the cables and what wood be the ballpark cost of this kind of repair in order to open up the whole basdement?

      thank you,
      Jan

      • Hi Jan,
        I am not an engineer.
        Thanks,
        Mars

    9. Hello!

      I am a manufacturer of safes and was wondering what you suggest the easiest way to Bolt Down a Steel safe on a Post Tension Slab? We generally use 1/2″ bolts with espansion shields or self driving anchor bolts. Your help is grealtly appreciated!

      • Hi Michael J,
        The length of your bolts is the main thing relative to the placement/location of the tendons.

        The tenant (your customer), the property management company, the building’s present owner may not know how thick the slab is or have access to PT engineer’s plan. In theory the tendons are placed in chairs or tied off so they remain a few to many inches below the surface of the slab/beams. You can’t see the location of the tendon. PT slabs are generally overengineered but many tendons are critical in placement and location. You do not want to pay for a tendon replacement/repair on the 12th floor of the bank building.

        My advice is don’t wing it. Call a testing lab and ask them what they charge for a tendon locate. If you can’t find one in yellow pages (Lab, testing) call the largest concrete contractor in town and ask them who they use. Usually, it is a minimum charge, an hourly charge for the technician, with mileage (depending on distance from site to lab) – a few hundred bucks and up, depending on regional economics.

        Mike, I would add PT Tendon Locate charges to your install pricing model for PT slabs, and on the site checklist something like is slab PT? if no, then customer assumes liability for PT tendon damage, if yes, then charges will be $X – the property manager should be able to furnish PT presence in slab info to tenant (PT? yes/no).

        Maybe create a “New PT model – The right choice for PT applications. Will not damage PT slabs!” which is the same as model X but with “PT” sticker (with banknote engraving and typeface) placed on inside of door and tendon locate/install factored in price point. After the locate you know to drill where the tendons are NOT, thusly, it does not damage PT slabs. Everybody’s happy.

        To prepare the lab tech for the locate the lab may ask for a set of PT plans to be available at site.

        some thoughts,

        Good luck Michael,

        Marshall

    10. Hi larry ..

      i would like to ask about applying a contruction joint in a PT slab , i have a symmetric building plan with 2 core wall areas , am trying to apply a construction joint … where are the restrictions that i cant locate my CJ..

      • Hi Hani,
        Who is Larry? Larry doesn’t run this blog but Marshall does, FYI.

        That is a question for your PT engineer as all tendons thru/ending at CJ will have to be designed/tensioned for length, load, etc.

        Tell PT engineer where you want the CJ and go from there.

        Take care,
        Mars.

    11. Hi Jeremy,
      I’m sure a company somewhere has put together a guide but I think you’ll be better off in the long run if you have the entire crew learn and become familiar with the various OSHA guidelines which apply to site, heavy machinery, electric hand tools, concrete, excavation safety, etc.

      A great resource are the “Toolbox Talks” which can be found using Google. Several sites offer them free and many are in Spanish. I would use the sign-in sheets and have a compiled reference notebook available at all times for anyone to refresh their knowledge on particular tasks and hazards.

      Another is the OSHA website. There are pamphlets which can be downloaded in PDF format.

      The best results come from an educated and aware crew who take personal responsibility for safety in addition to the “responsible person” on any particular jobsite running your crew.

      Thanks,
      Mars

    12. Larry,

      I am looking for a safety policies handbook that can be used for a post-tensioning crew. I have done several searches on-line, including the OSHA website, but have not had any luck finding a guide.

      Do you have any suggestions on where to find one or the best way to create my own?

      Thanks
      Jeremy

    13. My name is Rob. Read somethings you wrote on a blog about post tension slab cables. We live in a home in AZ and have a post tension slab that has all of the cable ends rusted and we now have a crack in our floor with water showing up (our carpet has been getting wet so we removed a section of it and found soil and water coming from the crack (this is very little water) the home was built in 1997. Do you think we may be looking at a big problem.
      Thanks Rob Sharkey

      • Hi Rob,
        That sounds like you have a problem. You may want to contact your insurance company, the builder, a local concrete contractor with PT experience, etc, for more advice. It also sounds like you may have a drainage or high water table issue. The ends rusting is due to the fact they may be exposed. Usually they are grouted over and can’t be seen.
        Take care,
        Mars

    14. Hi Larry,

      I’d call the person who wrote the specs.

      Entrained air is helpful in many ways and it seems a tennis court would benefit from the protection offered from freeze/thaw cycles and spalling more than your typical slab or parking lot. Air is typically increased in colder temperatures and increases workability during the pour, too. I agree with the sub.

      The blankets will help lengthen the hydration process by helping retard evaporation of water (better cure) and in colder environments (Fall in Southern Louisiana exposes the unprotected skin to frigid temperatures in the mid 70s, and yes they are wearing long sleeve shirts and hoodies now.) it maintains heat generated in during the chemical reaction (hydration). If environment is too cold (generally lower than 40 degrees) the reaction is slowed down and you may not achieve a proper cure. Blankets are fine but there is additional cost and curing compounds are more effective at retaining moisture (not permitted on your project). If temp is high enough then maintaining moisture can be done other ways – plastic, water spray, etc. Ask concrete sub how he will maintain moisture/temperature.

      Good luck – Mars

    15. When pouring a slab for a tennis court (in conjunction with a Plexicushion Prestige 2000) I understand the following:
      (1) No curing compounds
      (2) No calcium added
      (3) Water/Cement ratio of .45
      (4) Vaper barrier specs.

      However, I have the following question. Given the fall temperature is there any reason why air cannot be added to the concrete? The Concrete Contractor believes it is very critical that air be used.

      Also, the company installing the cabling is highly recommending that the conrete be covered with blankets after the pour?

      Thanks
      Larry Back

    16. If you haven’t poured yet I would correct the switch. It’s extra time and labor but build to plans. If already poured then send RFI to the engineer/architect.

      The issue where this would be a problem is on a construction joint where you would have to pull final tension before pouring slab contiguous with construction joint. This could delay pour by a month or so (depends on specs/cylinder breaks).

      It may not matter – often live ends are on one side and it makes it easier to pull in sequence. The end tension from live to dead end remains the same.

      Grab a rubber band with an index finger from left and right hand in the end loop. Pull with your left hand three inches to the left. Go back to no tension then pull with right hand three inches – same tension live or dead end.
      Mars

    17. I wanted to know if switching the live and dead ends of the post tensioned slab effetcs the design of PT Slab?


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