I need a single 3D or 2D rendering of a "piled-raft" foundation footing. I describe how to make it in a series of 10 steps (below) but reader will benefit if they can see it visually somehow. The illustration should be in black and white only, Gray shading is permissible. Standard architectural fill patterns for concrete, foam, soils etc. are OK. The final figure is expected to be published in a cabin-building book, with due credit to illustrator.
The construction description is below. Any questions, please ask for clarification if something is unclear!
Below are construction details for a piled-raft footing that may be suitable in locations where hand-digging holes to the frost line is made difficult by rocks, roots, or dense, compacted till. The pad footing is linked to driven pin pilings that extend downward to high weight-bearing soil. The friction with the pin pilings adds settling resistance to the pad. The footing form itself is built of XPS foam, which remains an integral part of the footing insulating against cold penetration from above.
Materials per footing:
XPS foam insulation (blue or pink) 1 sheet 2’x 8’ x 2”
Crack-resistant fiber-reinforced concrete mix (1 80# bag)
½” x 12” concrete anchor bolt
5/8” x 20’ rebar (number depends on driven depth)
Construction adhesive (1 tube)
Ground-marking paint (1 spray can)
Directions:
1) Excavate a square hole 3’x 3’ and ~12” deep. Pile excavated soil on a tarp for later use as backfill. Leave the bottom of this excavation level and soil on bottom undisturbed (important!).
2) Cut four pieces of XPS foam 2’x2’ in size. On 3, find the center, and cut a circular hole with 9” radius (18” diameter) using jig saw or drywall saw. Bond these together with foam-compatible adhesive along the circular cut edge. On the fourth piece of foam, find the center and cut a circular hole with 4” radius (8” diameter). Bond this piece to top of the other three.
3) Lay the XPS form flat on bottom of excavation exactly where the footing/pier will be. Reach inside and spray paint the ground within the form. Then remove the XPS foam form and set aside.
4) Within the painted circle, drive an 8’ length of rebar into the ground as far as it will go, or until just 8” protrudes, whichever comes first. For ease, drive this with a hand-held fence post driver and finish with hand sledge. Cut off protruding rebar 8” above ground (a Milwaukee 12V cordless subcompact bandsaw is an excellent tool for this).
5) Continue in this fashion until you have driven 6 rebar pins, well-spaced, into the footing area, but none closer than 2” to the painted outline of the footing.
6) Using a rebar bender tool, bend the protruding length of each piece of rebar to a ~ 90-degree angle, 3 or 4 inches above the ground. Keep all bends within the footing outline. These bends will lock the rebar into the concrete raft when the footing is poured.
7) Place the previously constructed XPS form on the painted ground surface, enclosing all of the driven pin piles. Mix fiber-reinforced concrete to specifications. Weight form down with cinderblock or large stones and pour mix until it is flush with top of the form.
8) In the center of the 8” diameter hole, insert 12” anchor bolt, pushing through the wet concrete until it hits the ground, leaving 4” exposed. Ensure it’s centered and plumb. Cover exposed concrete with plastic and let the footing cure 72 hours.
9). Cover the form with dirt excavated originally. Grade to drain away from the top of the footing. Seed, and cover with straw until vegetation is established. (Omit this step from drawing....).
10) An 10" diameter round wooden pier will be set on top of this footing. The protruding bolt in the footing will insert in a hole drilled in bottom center of the pier.
How well does the illustration help convey the build? It should be as simple as possible to convey the idea to a novice builder. It should show the finished footing in the ground. Cut-away rendering fine. 2D or 3D fine-- whatever communicates most clearly. Final print should be digitally conveyed in high-res (300 dpi) or higher, preferably TIFF format. (sorry, I'm not CAD conversant)
Designers,
The piled raft footing project will end soon and within the next 4 days we will decide the winning entry. The 6 designers that entered all submitted technically accurate drawings/plans and were willing to make changes along the way. Your work is excellent, and all are deservedly nominated.
Selection of the winning entry will be made by the book's authors, editor, and book designer based on (1) How well the rendering communicates the details of the footing construction, (2) how visually appealing it is, and (3) how well it fits in with the interior book design and other illustrations.
These are subjective calls, and making these decisions will be difficult. Thank you for your patience as we select the winning entry, and again, for your impressive work.
MDK
MDK
Buyer