concrete formwork question
concrete formwork question
(OP)
I have a situtation where perimeter masonry walls support an outdoor patio. The owner wants to use a structural reinforced slab instead of slab on grade. I know there are ways around having to shore the slab (light gauge framing supporting slab, composite deck, steel joists, etc.), so this is just a general question. Have you ever been in this type situation where the formwork was required but would be enclosed by the new concrete structure and have to be... abandoned for lack of a better word? Thanks.






RE: concrete formwork question
Dik
RE: concrete formwork question
RE: concrete formwork question
Your post does not mention about your region. If you are in a region where there are no frost protection requirements, then it is possible to place the slab directly on soil/base without using any sacrificial forms or frost protection measures.
RE: concrete formwork question
I can use a composite steel deck to achieve the spans he wants, but would be cheaper to do some metal decking (non-composite) as form work that is shored a couple/few times between permanent supports. Like JAE said, this would cause concerns with termites though with abandoned forms. Maybe form work from treated lumber?
RE: concrete formwork question
Dik
RE: concrete formwork question
Use form deck and reinforce with rebar or do one of the other ideas above.
RE: concrete formwork question
RE: concrete formwork question
Dik
RE: concrete formwork question
Becareful with cardboard void formers. I used them once and they collapsed when the concrete was placed. Very costly.
RE: concrete formwork question
You should have some openings for ventilation... Can have a louvred opening, or simply a steel grate/wire opening to keep birds and rodents out...
asixth:
Cardboard ones work OK, as long as they're kept dry prior to placing and contractors often wrap them in poly and provide a 1/8" or 1/4" masonite board on top to keep the rebar chairs from poking through.
Dik
RE: concrete formwork question
bigenginner - I definitely agree with JAE & Hokie, do not depend on the metal deck for any composite action. Dik makes a good point about providing a couple of screened openings to ventilate the enclosed void. You don't mention the plan dimensions, but you may be able to lighten up the deck gauge by fabricating a simple truss from angle stock to hang off the walls and provide additional support at the middle of the deck span.
Ralph
Structures Consulting
Northeast USA
RE: concrete formwork question