Introduction: ADA-compliant Picnic Tables

About: CrLz : Ideas, ideas and ideas - Love it when I get one hammered out and working. Seems like there is plenty of room for creativity, in between cheap goods and expensive solutions, and beyond those boxes...

I had the fortune to build these picnic tables with the Friends of Kalamani & Lydgate Park for National Make a Difference Day and Earth Day. The design is well planned and provides wheel chair seating at both ends of the table.  Anyone wishing to build a single table can use these plans and figures.  Multi-table builds additionally will benefit from FKLP's work-flow processes.

A sweet jig was used to quickly assemble the trestles, standardizing the tables and ensuring ADA compliance.  The detailed saw setups make cutting parts short work.  FKLP's thoughtful assembly steps simplify accurate construction.  Lastly, I have included some build suggestions and a survey of failure mechanisms.

A single person should be able to finish a table in a weekend.  Approximately 25 volunteers, working two half-days, can assemble 10+ tables.  These tables are strong, heavy and durable, excellent for years of use.

Step 1: Tools, Materials and Plans

Attached to this Instructable are

  • 3D full scale model of the picnic table, both in shareable open format "ADA Compliant Picnic Table.dae" and in SketchUp format "ADA Compliant Picnic Table.skp". The file can also be downloaded from the Google 3D Warehouse listing.
  • The table plans and basic materials list "Picnic Bench Plans.pdf" with a QR-code that links back to this Instructable.
  • Assembly instructions "Table Assembly Steps.pdf" with relevant measurements labeled.

Anyone seeking to modify the design will find the 3D files very useful for recalculating measurements. A two-sided handout of "Picnic Bench Plans.pdf" and "Assembly Steps.pdf" can be given to table assembly teams to guide table building.

Budget $400 per table. Actual cost was ~$350 per table for the builds in 2011 and 2012. If you are using these plans to make a single table for your home, keep in mind the table's sheer weight of ~300 lbs. The weight can be reduced by using shorter 2x12's (also shorten the 2x4's and recalculate their angles). Alternately, try different lumber, perhaps non-treated. At your store, collect lumber and lift for weight estimate.

The materials for a single table are:

  • 5pieces [ 2" x 12" ] by 10' treated wood
  • 2pcs [ 2" x 6" ] by 12' treated wood
  • 1pcs [ 2" x 6" ] by 10' treated wood
  • 1pcs [ 2" x 4" ] by 8' treated wood
  • 16pcs 1/2" x 31/2" stainless steel carriage bolt, with nuts and washers
  • 1 lb. 16 penny galvanized nails (~50pcs)*
  • 1/3lb. 9 penny galvanized nails (~35pcs)*
  • 1/2 gal floor enamel paint**

*FKLP used spiral-shank stainless steel nails.
**FKLP used different paint and quantities from listed in the schematic-materials (primer and top coat instead of 1/2gal floor enamel paint).

Prep-day tools for a large-volunteer program (3 saw-stations, 2 sanding-stations and 1 paint-station):

  • 4 20' x 20' shade / rain tents
  • Tarps for ground cover at paint spray area
  • Extra tarps for wind block, if necessary
  • Lots of extension cords
  • 3+ power bars with internal breaker switches
  • 15+ Saw Horses
  • Three 24" x 16' work platforms to set up saw stations
  • Sliding Miter Saw
  • 3 Miter Saws
  • Scrap 2 x _X_ boards for rests and board stops
  • Many 3" deck screws to secure saws and stops
  • 3 pliers for pulling staples from lumber
  • 2 wheel barrows
  • 2 belt sanders
  • ~10 sander belts, ~80-grit
  • Paint sprayer**
  • Air compressor**
  • Paint-operator safety equipment (goggles**, respirator**, disposable clothes)
  • Paint sprayer cleanup equipment**
  • Four sturdy poles, ~10' long to carry wet parts
  • Stacking spacers for wet parts, ~20pcs per table
  • Work gloves
  • Safety Glasses
  • Cold water

**FKLP used a primer and top coat instead of 1/2gal floor enamel paint.

Assembly day tools (2 jig-stations, 4 table assembly-stations and 1 paint station):

  • 3+ 20' x 20' shade / rain tents
  • Tarps for ground cover at paint spray area
  • Extra tarps for wind block, if necessary
  • lots of extension cords
  • 3+ power bars with internal breaker switches
  • Custom trestle assembly jig***
  • 6 Drills
  • 10+ 1/8" drill bits
  • 2 1/2" spade-drill bits
  • 2+ Socket wrenches for 3/4" nut and bolt
  • 20+ Saw horses
  • 8+ 20oz hammers
  • 4+ Nail punches for 16d nails
  • 4+ Tape measures
  • 4+ Carpenter squares
  • 4+ Pencils
  • Paint sprayer**
  • Air compressor**
  • Paint-operator safety equipment (goggles**, respirator**, disposable clothes)
  • Paint sprayer cleanup equipment**
  • Four sturdy poles, ~10' long to carry wet tables
  • Scrap 2x6 boards to place under wet table feet
  • Work gloves
  • Safety glasses
  • Cold water

**FKLP used a primer and top coat instead of 1/2gal floor enamel paint.
***The custom assembly jig is explained in the following step.

Step 2: Trestle Assembly Jig

The trestle jig allows quick and correct layout of components. This will ensure accuracy / ADA compliance and hasten assembly. Five+ tables will be faster using a jig.  One jig per two table-assembly teams is a good balance (i.e. 1 jig per 5 tables).

Jig materials:
  • 4' x 8' sheet of 3/4" plywood
  • 10pcs stop-blocks made from leftover sections of 2" x 6" in 3" lengths
  • 6pcs  angle-blocks made from leftover sections of 2" x 4" cut in 45o triangles
  • 12pcs 31/2" deck screws
  • 6pcs 2" deck screws
The tools used are:
  • 48" Framing square
  • Tape measure
  • Pencil
  • Miter saw
  • Drill
  • 1/8" drill bit
  • 2" Hole saw
  • Phillips-head screw drill-bit
  • Drum-sander drill attachment
To make the jig, measure out the trestle outline:
  1. Mark the long-side midpoints.
  2. Connect the marks, making the mid-line, running across the plywood.
  3. Measure 15 1/2" up the mid-line and draw a line extending 31" (62" total) in both directions, the top edge of the seat-support.
  4. Measure 27 1/2" up the mid-line and draw a line extending 17" (34" total) in both directions, the top edge of the table-support.
  5. From the right end of the table-support line, measure inwards 7" and make mark #1.
  6. From the right end of the table-support line, drop a line straight down to the seat-support line (12" down) and make mark #2.
  7. Draw a straight line connecting marks #1 and #2, continue to the bottom edge of the plywood. This is the right leg's outside edge.
  8. Repeat steps 5-7 on the left end of the table-support line, outlining the left leg.
After stenciling the trestle, add stop blocks along the top and sides of each stenciled board.  The stop blocks should be at least 3" high and should be buttressed to ensure their stability and durability.

Finally, cut hand-holds in the plywood to make carrying easier.  Use a 2" hole saw and cut two holes along the top edge of the jig. Sand and bevel the edges of the holes using a drum-sanding attachment for a drill.

Step 3: Cutting and Priming

A week before assembly, a small set of  ~15 volunteers prep the parts from the lumber-stock.

The lumber for a large build will be truck delivered before the prep-day.  Choose a good delivery spot and specify the orientation of the boards.  Pick a location that is secure.  Visualize the prep work-site setup, ideally organized with minimum walking and turning while carrying lumber, cutting, sanding, priming and stacking to dry (see FKLP map example).

Check the lumber when delivered.  On both builds, FKLP's supplier substituted different lengths of lumber!  Thus, if necessary, adapt the workflows and ensure there is enough stock.  Cover with tarps to keep dry.

The ADA Accessibility Guidelines for Buildings and Facilities, fixed or Built-in Seating and Tables (ADAAG 4.32) are:
4.32.3 Knee Clearances. If seating for people in wheelchairs is provided at tables or counters, knee spaces at least 27 in (685 mm) high, 30 in (760 mm) wide, and 19 in (485 mm) deep shall be provided.
Do not build to the minimum! Add error tolerances of +1/2" to the minimums. ADA clearances spec'ed by these plans are 27 1/2" high, 41 1/2" wide, and 19 1/2" deep.  Use 1/8" as the smallest resolution for measurements.  Keep in mind that typical lumber is "dimensioned lumber".  That is, the named dimensions are larger than the finished dimensions:
specified.....2 by 12 actually.....1 1/2 by 11 1/4 inches
specified.....2 by 6 actually.....1 1/2 by 5 1/2 inches
specified.....2 by 4 actually.....1 1/2 by 3 1/2 inches
Five 2 x 12 x 10' make 2 seats, 2 table-sides and the table-middle.
Two 2 x 6 x 12' makes the two seat supports and four legs.
One 2 x 6 x 10' makes three table supports.
One 2 x 4 x 8' divides into two leg braces.
The cut plan shows these breakdowns.

Set up the following saw stations in two tents.  Each tent can accommodate 2 stations running parallel, along the length of the tent. Reconfigure saws and run each batch separately if you have only a few saws. Station #2 and the other stations, in turn, is about the minimum comfortable setup.  FKLP ran #1, #2, #4 simultaneously, then reconfigured and ran #2, #3, #5, #6 simultaneously.

#1 Saw Station: Trimming 2 x 12's to 10' length
  • 3 volunteers
  • Set up the Sliding Miter Saw with a stop 10' further down work surface. Sliding saw is necessary to cut 12" width.
  • Trim the leading edge of the 2 x 12 and then to the full 10'.
  • Volunteers should watch for good seat boards, smooth faces and free of knots and stack separately for bevel crew.
#2 Saw Station: Beveling corners of Seats**, Table Sides** and Supports
  • 2 volunteers
  • Set up two Miter Saws, 9' 7" apart.  Set both blades to a 45º outward angle. (Outward = leading saw +45º. trailing saw -45º, see saw setup and figure for beveled corners).
  • Set or mark stops 2 1/2" outside of each blade.
  • 2 x 12 boards will fit between stops snug, allowing the two corners by saws to be trimmed off- forming a table side board.
  • Flip 2 x 12 boards to cut the remaining two corners forming a seat board.
  • Volunteers should keep track of seat, side and middle board quantities, ensuring correct # of parts per table.
  • Supports from #3 and #4 can be individually beveled as become available.
  • Finished parts sent to sanding on all cut edges
#3 Saw Station: Trimming Table Supports to 34" length
  • 1 volunteer
  •   Set up a saw with a 34" stop further down work surface.
  •   Trim the leading edge of the 2 x 6 x 10' and then three support's to full 34" length.
  • Send all supports to #2 Saw Station
#4 Saw Station: Trimming Seat Supports to 62" length
  • 2 volunteers
  • Set up a saw with a 62" stop further down work surface.
  • Trim the leading edge of the 2 x 6 x 12' and then the support's full 62" length.
  • Send support to #2 Saw Station
  • Send remaining board to #5 Saw Station

#5 Saw Station: Trimming Legs to length and correct angle
  • 1 volunteer
  • Set up a saw with a 30o angle.
  • Trim a ~ 6" long piece from scrap 2 x 6 to make a 30º stop.
  • Set the stop 317/8" further down the work surface. The 30º will butt against incoming, angled boards flush (see saw setup and figure for angled cuts).
  • With the leftover 2 x 6 from #3 Saw Station, cut two legs to length.
  • After all legs are cut, cut a small "toe" off each leg on the ground-face (saw to 0º and stop 5/8").
  • Send finished parts for priming, no sanding
#6 Saw Station: Trimming Braces to length and correct angle
  • 1 volunteer
  • Set up a saw with a 21º angle.
  • Trim a ~ 6" long piece from scrap 2 x 4 to make a 21º stop.
  • Set the stop 39 1/4" further down the work surface. The 21º will butt against incoming, angled boards flush (see saw setup and figure for angled cuts).
  • Cut two braces from a 2 x 4 x 8'.
  • Send parts straight to priming, no sanding
As specified, sand to gently round the corners of edges that are likely to contact picnickers.  Two volunteers with belt sanders can work as parts become available. Sanded parts are sent for priming.

FKLP primed all parts with a water based primer.  Parts were stacked across long carrying poles and primed, flipped and primed on remaining sides.  After a short drying period, two volunteers stacked parts to cure.  Spacers cut from scrap wood were inserted between all layers.

**Note the beveled corners on the seats and table side boards are not specified on the schematic but are detailed on the 3d model.

Step 4: Assembly and Painting

Assembly day gets started at 7:30, setting up tents and dividing the stack of primed wood. Two 20' x 20' sun-shade tents side by side provides space for two trestle teams and four table teams. Separate the painting tent far enough to isolate the paint spray. Lay tarps down on the ground to protect the area from paint.

Each team is ~4 people with a designated foreman. Foremen are picked by the organization prior to the build date. When volunteers arrive, have sign in sheets for each team with foreman listed as the first name. Volunteers sign their names in available spots, thus assigning themselves to a team & foreman.

Trestle teams get started early assembling. Two volunteers use the jigs to align and nail the trestles together. Two volunteers drill the bolt holes using the 1/2" spade bits. Place scrap wood under the trestle to avoid breaking out the bottom face as the drill bit comes through. The remaining four volunteers insert and tighten the carriage bolts. Nuts and washers go on support face sides, not leg faces.

Tables teams follow these assembly steps:

  1. Attach middle board to 34" table support, center on center. Use 1/8" drill bit to set nail holes. Use nail sets to avoid marring table surface. Ensure all boards snugly fit against each other.
  2. Turn assembly upside down and attach 2 x 4 braces. Braces should be offset around the support middle.
  3. Attach trestles to braces, same offsets. Legs go on outside.
  4. Turn assembly right side up, onto trestles. Square trestle to table top. Check that clearance depth is > 19"! Attach to middle board.
  5. Attach the two table side-boards. These should overlap the support ends by 1".
  6. Attache the two seats. These should also overlap the supports by 1".
  7. Carry finished tables to painters, or staging area for painters. Four volunteers lift the table, a volunteer at each corner.

The painting team applies the top coat and moves completed tables to the drying area. Four people pass long poles under the seats of painted tables to lift and carry the wet tables to the drying area. Additional volunteers position scrap wood under each foot, directing where to set the table down. Allow at least one day for paint to cure before moving.

Step 5: Build Suggestions and Failure Analysis Summary

Suggestions for large builds:
  • The first table is usually complete in ~1hr,  the second table in ~1/2 hour and subsequent tables in ~20 min.  Once the volunteers understand the steps and their team, the work will go very fast.  Thus, ~3 tables is a good quota per team, leaving time for setup, instruction and cleanup.
  • Forethought for volunteer safety & comfort will go a long way towards a better build.  Safety should be a priority.  Comfort is also very important- exhausted volunteers are prone to bad decisions and injury.  For example, tents not only help with sun-burn, but reduce heat exhaustion and headaches from eye-glare.  FKLP could never provide too much ice water.  Anyone working or assisting with painting is likely to ruin their apparel.  Plan ahead to avoiding frustration / anger.
  • Finishing by lunch, and providing lunch, goes a VERY long way towards a happy project.  Making the tables is one goal, but enjoying the community and social nature of the project is perhaps more important.  Tired, hungry volunteers are not fun; they are a mob with power tools...
  • Be prepared to juggle setups and work flows.  Any large build will encounter problems. Have a work-site coordinator who floats and addresses these problems.  The coordinator should brief foreman and manage the team sign in.  A coordinator watches for bottlenecks in the workflow and shifts volunteers as necessary.  Ensure no one is stuck waiting for work, something volunteers have little patience for.
  • Pay attention to people with professional/practical experience.  Many volunteers will gravitate towards projects that overlap their skill sets.  Often very knowledgeable people will introduce themselves for the first time on build days.
  • Issue two PR releases to gather volunteers.  A general announcement ~1 month in advance, followed by a nice write-up ~3 days in advance.
  • Use the prep day as a "shakedown".  Volunteer turn out will be less, if it seems too small, get aggressive with recruiting for assembly day.  Take note of any tools missing or in short supply and ensure sufficient amounts for assembly day.
  • Use power-bars with built in breaker-switches for branching electricity if wall-outlet connections are limited.  Running multiple power tools off a single outlet will not trip the current limiter often. Most tools will not be simultaneously in use.  However, current faults will happen and it is a shorter walk to the center of a work area than all the way to the building breakers.


Each table should have a lifespan of ~10 years (~4 years with no maintenance and heavy use). The most common failures, greatest to least significance, are:

1. Leg Fracturing
The tables are very heavy when finished.  When moved by users, the force on the legs can be tremendous.  Often the legs will fracture along the grain, up from the "foot". Doubling up the legs below the seat support could mitigate this.  Alternately, fixing tables to specific locations can prevent this.

2. Site non-compliance
Although the table provides clearance for wheelchairs,the area where the table is placed may not be fully compliant.  Keep in mind wheelchair access to the seating is also important.  This means ADA compliant:
  1. parking,
  2. path to the table,
  3. placement surface with space to back away from the table and move around the table 
Additionally, when placing the table on a soft surface, the feet may sink far enough to prevent wheelchair access.  Imagine an entire hypothetical visit for a handicap visitor to ensure compliance.  Visit the ADA Standards Homepage for more information and ADA Accessibility Guidelines.

3. Nail corrosion / Nail hole rot
The nails and nail-holes securing the seating and table boards are prone to water ingress, causing nail shanks to rust and nail holes to rot away.  Both will cause failure, typically seen when lifting the table by the seats (board tear-out).  Extra careful painting + sealing the nail holes can help prevent this.  Periodic maintenance painting + replacement can also delay this.

4. Bolt corrosion
The trestle bolts will eventually fail.  Stainless steel bolts and painting will delay the failure. Periodic maintenance painting can help.

5. Paint failures (Initial Placement, Mechanical, Chemical)
Paint failure was common, but surprisingly only causing mild failures.  Tables get scratched when moved.  Mechanical and chemical wear becomes appreciable after a few seasons.  These effects are, however, mostly cosmetic.  FKLP primes and then paints a top coat to increase the paint durability. Periodic maintenance painting can overcome this.

6. Board splitting
Splitting of the 2 x 12 starting at the ends and progressing the length of the board was common.  However, these splits rarely crossed nail holes and generally had little effect.

7. Theft and Graffiti
Hard to tell how much an issue theft is, but seems low.  Graffiti is surprisingly low.  Some tables in Kauai have chains installed to fixed areas.  Involving community to build tables generates a lot of pride in the project and deters vandalism and theft.
Mahalo to the Friends of Kalamani & Lydgate Park, the Church of Jesus Christ of Latter Day Saints, Kauai Department of Parks & Recreation, the Sunshine Rotary Club, YWCA of Kauai and all the volunteers that helped in 2011 and 2012!
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