Proposed Second Floor Slab

Here is the proposed December construction project.

  1.  Change the existing G.I. roof above the bedroom into a concrete second floor slab to make the roof sturdy as it is being used as a garden.
  2.  Move the computer room to the front of the property to prevent customers from getting access to other parts of the house.
  3.  Merge the existing computer room and bedroom into a single open area to function as a sala and dining room.
  4.  Convert the existing sala/dining area into a two-bedroom area.
  5.  Raise the floor line above the road grade line.
Panoramic View of Property
Main Entrance

Super Quick and Really Dirty Figure 1 – Existing property

Super Quick and Really Dirty Figure 2 – Proposed

Location of Main Beam (Left Beam)

FINAL DESIGN OF SECOND FLOOR CONCRETE SLAB

FIVE (5) REINFORCED COLUMNS
Two (2) Columns (Top Left and Bottom Left)
Column Size: 200mm x 400mm x 10M
Vertical Bars: 8 x 16mm ∅
Ties: 10mm ∅
Three (3) Columns (Top Right, Center Right, Bottom Right)
Column Size: 200mm x 400mm x 10M
Vertical Bars: 6 x 16mm∅
Ties: 10mm ∅

FIVE (5) COLUMN FOOTINGS
Thickness: 350mm
Size: 1.0M x 1.0M
Bottom Bars: 16mm ∅
Excavation Depth: 1.5M

Four (4) REINFORCED BEAMS
Two (2) Beams (Top and Bottom)
Size: 200mm x 400mm x 3M
Steel Bar: 6 x 16mm ∅
One (1) Beam (Right)
Size: 200mm x 400mm x 6M
Steel Bar: 6 x 16mm ∅
One (1) Beam (Left)
Size: 200mm x 400mm
Steel Bar: 8 x 16mm ∅
Stiffener Bar: 4 x 12mm ∅

REINFORCED CONCRETE SLAB
Thickness: 100mm
Area: 3M x 5.6M
Top Bar: 12mm ∅ @ 150mm O.C. Grid Pattern
Bottom Bar: 12mm ∅ @ 150mm O.C Grid Pattern

COST ESTIMATE

Price List of Construction Materials

Price Quotation from EverHill Hardware in Commonwealth Avenue near Don Antonio Subdivision
Telephone Number: 932-3053
Quotation Date: 09 December 2017
MATERIALQUANTITYUNIT PRICE (PHP)
Steel Bar 8mm diameter 6M length1 each100.00
Steel Bar 10mm diameter 6M length1 each130.00
Steel Bar 12mm diameter 6M length1 each195.00
Steel Bar 16mm diameter 6M length1 each330.00
Portland Cement1 bag205.00
Sand1 cubic meter750.00
Gravel 3/4"1 cubic meter1,050.00
Hollow Blocks 4"1 each12.00
Hollow Blocks 6"1 each13.00
Plywood 1/4" 4'x8'1 each385.00
Coco Lumber 2"x2"x8'1 each72.00

Cost Estimate of Reinforcement Bars

ELEMENTBAR DIAMETERQUANTITYUNIT PRICE (PHP)TOTAL PRICE (PHP)
Footer (F) 16mm17330.005,619.00
Top Left Column (C1)16mm83302,640.00
Top Left Column Ties10mm6130780.00
Bottom Left Column (C1)16mm83302,640.00
Bottom Left Column Ties10mm6130780.00
Top Right Column (C2)16mm63301,980.00
Top Right Column Ties10mm6130780.00
Center Right Column (C2)16mm63301,980.00
Center Right Column Ties10mm6130780.00
Bottom Right Column (C2)16mm63301,980.00
Bottom Right Column Ties10mm6130780.00
Left Beam (B1)16mm83302,640.00
Left Beam Ties10mm6130780.00
Top Beam (B2)16mm63301,980.00
Top Beam Ties 10mm6130780.00
GRAND TOTAL43,320.00

NEW BUDGET-CONSTRAINED DESIGN

ASSUME CONCRETE SLAB WILL FUNCTION AS PLAIN ROOF

Budget-Constrained Design
FOOTINGArea0.80M x 0.80M
Thickness300mm
Reinforcement Bar12mm @ 150mm C/C
Excavation Depth1.2M
COLUMN C1 (Two Left Columns)Dimension225mm x 300mm x 10M
Reinforcement Bar8 x 12mm
Stirrups8mm @ 150mm C/C
COLUMN C2 (Three Right Columns)Dimension225mm x 300mm x 10M
Reinforcement Bar6 x 12mm
Stirrups8mm @ 150mm C/C
BEAM B1 (Left Beam)Dimension225mm x 300 mm x 5.6M
Reinforcement Bar8 x 12mm
Stirrups8mm @ 150mm C/C
BEAM B2 (Top and Bottom Beams)Dimension225mm x 300mm x 3.0M
Reinforcement Bar6 x 12mm
Stirrups8mm @ 150mm C/C
BEAM B3 (Right Beam)Dimension225mm x 300mm x 5.6M
Reinforcement Bar6 x 12 mm
Stirrups8mm @ 150mm C/C
SLABArea3.0M x 5.6M
Thickness100mm
Reinforcement BarTwo layers
10mm and 8mm alternate, grid @ 100mm C/C

Design based on http://www.civilprojectsonline.com/building-construction/thumb-rules-for-designing-a-column-layout-building-construction/ and http://www.civilprojectsonline.com/civil-projects/minimum-standards-for-structural-design-rcc-structures/#more-1362

NEW COST ESTIMATE

Cost Estimate of Reinforcement Bars
Stirrups for columns and beams 5-1/2″ x 13-1/2″ (concrete cover-1-1/4″ or 31.75mm )
Fabricated Rebar Bending Tool
Figure A
Figure B
Figure 10A – Center Column – Please note footing bend directions
Figure 10B – Center Column
Figure 11A – Corner Column – note footing bend directions
Figure 11B – Corner Column – another view

FOOTING REBARS

Footing Rebar with Sample Element
Footing Rebar Whole
Electrical Layout – 8 junction boxes spaced 1 meter apart for 8 pinlights

REFERENCES:

http://www.unisdr.org/files/10329_GoodBuildingHandbookPhilippines.pdf

12 thoughts on “Proposed Second Floor Slab”

  1. Both are ok but fig 3 is easier to execute because you don’t have to demolish portions of the existing wall. Figure 4 is less “obstructive” though.

  2. On the proposed partitioning, occupants of the 3 bedrooms might not be able to get out if fire breaks out in the dining area. Just my thoughts…

  3. Thanks, I’ll modify the floor plan later. There is an existing door facing the garage at room 2. I’ll probably have to keep it as it is.

  4. You could make the 5.6m beam bigger (say 8 x 16mm) and the columns supporting it bigger than usual (say 8 x 16mm). Consider placing a stiffener beam across the left and right beams. Your beam structure would look like an ocho. Without this stiffener beam (4 x 12mm), papagpag yung slab mo pag nag-jumping jack ka. The sizes I mentioned presume that the “roof deck” would, in the future, become a room with a GI roof above it.

  5. Okay naman except:
    Left columns: 8 x 16mm, right columns: 6 x 16mm (overdesigned yung 7)
    Footings: 1m x 1m, depth of 1.5m is ok
    Beams: Yung 2 pcs na 7 x 16mm, you could reduce these to 2 pcs 6 x 16mm
    Slab: ok, or as discussed

  6. Don’t forget to include in your estimate the forms (1/2″ thick form plywood) and scaffolds (2″ x 3″ coco lumber) that would support the beams and the slab. You will also use a significant amount of GI wire.

    Concrete mix is 1:2:4 (cement: sand: gravel) by volume

  7. Apparently all the project owner wants, due to budget constraint, is to have a sturdy roof above the area. The structure design is typical for a bungalow (except for the use of 8mm as stirrups) and if we could surmise that the weight of the slab is close to the weight of trusses and GI roof if it was a bungalow, then it’d be well and good.

    Consider reducing the thickness of the slab to reduce the load on the beams and columns. You save more by doing so and make the structure “safer” for the present occupants (but not for people who would use and probably modify its use later).

  8. Sobrang haba ng bends pero pwede na yan; sayang kung puputulin. Yung corner columns, maitatayo ba kung ganyan ang direction ng bends? Stirrups look ok.

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