Full Structural Engineering Service Available
Structural Engineering for Domestic Residences and Home Units Commercial Office Buildings, Public Buildings and Industrial Buildings. Civil Engineering Designs for Retaining Walls, Storm water Drainage Systems.
We can design your concrete floor slabs:
- Concrete Raft Floor Slab
- Concrete Suspended Floor Slab (all types)
- Concrete Floor Slab on Ground
- Concrete Foundations & Concrete Pier Pads
- Concrete Structural Beams
We can design your steel structural components:
- Steel Portal Frame
- Steel Universal Beams (UB)
- Steel Column
- Steel Roofing Structure
- Steel Roof Decking
- Steel Base Plates and Anchor
- Steel Bracing
All structural engineering designs are certified by our Business Associates: Practicing Structural Engineers
- Kneebone, Beretta & Hall P/L
- Mr T. Hall (F.l.E. Aust CPEng)
RAFT SLAB REQUIREMENTS
Level the area as much as possible, where the proposed floor slab will be situated by excavation, scraping etc. Dig the edge beam at the perimeter of the proposed slab at a minimum of 500mm deep and 300mm wide. Clean out the edge beam trenches, no residue soil or fill to be in the edge beam trenches. Pour 50mm of clean fill or sand under the proposed floor slab as a base (floor slab only…not trenches and beams) Spread the polythene (plastic) black or orange blanket over the proposed floor and trench area. Do the same with the floor slab beams as shown on the engineers’ drawings. Floor slab beams are 500mm deep and 300mm wide with an 45degree up angle, see engineers drawings.
Built the concrete slab timber formwork around the perimeter of the concrete slab. Make sure the thickness of the concrete floor slab is according to the structural engineering drawings. In most cases the floor thickness is 100mm or 120mm (check the engineers’ drawings).
Prepare the trench mesh that will fill in the edge beam trenches. Tie with trench mesh wire the layers of trench mesh (top & bottom) as approved by the structural engineers’ drawings. In between the trench mesh layers (top & bottom) tie down the tie bars at nominated centres’ with tie wires.
Place the steel mesh support chairs in the edge beam trenches to support the two layers of trench mesh and tie bars as per engineer’s drawings. Make sure there is a clear space top and bottom of at least 20mm from the bottom and top of the edge beam trenches, the trench mesh should be in the centre of the trenches with the concrete surrounding the mesh.
This is also required for the floor slab beams, these are beams in the floor slab at a 6.0m centres see engineers drawing.
Check the engineers’ drawings for the specification of the floor mesh or fabric. The floor mesh is specified as SL 72, 82 or 92 depending on the size or use of the proposed concrete floor. Place the steel support bar chairs on the floor area as per engineers’ specification or drawing. Place the floor mesh on the support bar chairs, tie the floor mesh to the next floor mesh to fully cover the slab with the floor mesh from end to end. The floor mesh should overlap over the installed trench mesh as per engineers’ drawings. Make sure the floor and trench mesh are in position and tied down by tie wire. The floor slab mesh should overlap the next floor mesh with a minimum of 450mm to provide an uninterrupted top layer of floor mesh over the entire concrete floor.
At this stage when the steel mesh and trench mesh are in position, call in for a steel inspection by either the local council or structural engineer, to approve the steel in position stage before the pouring of concrete. Make sure that the steel inspection is approved by the council or structural engineer before ordering the concrete to be poured to form the floor slab with the edge and floor slab beams in position.
RAFT SLAB NOTES:
- Characteristic concrete compressive strength (F’c) in accordance with AS. 3600 to be 32Mpa.
- Maximum slump to be 80mm.
- Concrete in slab to be mechanically vibrated during placing.
- Cure concrete by keeping constantly damp for at least 5 days after placing.
- Reinforcement to be supported on bar chairs spaced at every 5thwire in both directions.
- Grade finished ground surface to divert water away from slab on all sides and to prevent ponding.
- Install “TERMI MESH” or “Kordon” blanket strip or similar termite protection system as per manufacturers’ specifications on the slab as shown on the manufacturers’ brochures and drawings.
CONCRETE FLOORS ON FILLED-IN GROUND (DAMS, RUBBISH TIPS, MINE SUBSIDENCE AREAS AND FILLED LAND)
IMPORTANT NOTE: If the land is subject to unnatural filling, example, a previous dam was on the property, and the dam was filled in with filling soil, any construction on the site of the previous dam, must be “peered” with concrete piers at a min of 400mm dia and @ 2.0m centers. The concrete pier must be of solid concrete with no steel rods attached! The concrete piers are to “hold up” the slab or foundations of the slab. Before construction of the concrete slab, drill the piers @ 400mm dia on the perimeter of the slab and internal beams, drill to shale level or at least 2.0m down. After the piers have been poured with concrete, the floor slab or foundations can be constructed. Make sure that the floor slabs and foundations are on top of the concrete piers.
DO NOT USE RUSTED MESH AND/OR TWISTED REINFORCEMENT RODS……!
ALWAYS USE “FRESH/CLEAN” FACTORY SUPPLIED MESH AND REINFORCEMENT RODS, RUSTED METAL IN CONCRETE CAN CAUSE “CONCRETE CANCER” THIS WILL CAUSE THE CONCRETE SLAB TO FAIL /COLLAPSE.
IMPORTANT NOTE: Before pouring a concrete slab, a steel inspection is required by most County or Local Councils or Authorized lending organisations. DO NOT POUR CONCRETE BEFORE YOUR STEEL MESH HAS BEEN INSPECTED. If the structural design drawing has been drawn up by John Gersteling & Associates, we have been authorised to perform the steel inspection by T Hall of Kneebone Beretta and Hall structural engineers of Penrith NSW. Please apply for a quotation for the steel inspection. A certificate will be issued for your local council to certify that an inspection was carried out/performed and signed off by the structural engineer.
WAFFLE FLOOR SLAB
Waffle concrete floor slabs are popular with “project/exhibition homes” builders and builders that are cost sensitive in obtaining a building project. A Master Builder would not used this type of floor construction if he/she is an experienced builder, he/she knows the pitfalls of constructing a concrete base floor. Please note that polystyrene is not a building product but a packing material that is not suitable in the construction industry. Cool room walls are made with polystyrene because these cool rooms are inside a building….not exposed to the elements of weather, rain, storm or heat from sunlight. Polystyrene blocks take up space within the slab so that there will be less concrete needed and concrete costs have been on the rise! I have personally seen the construction of a waffle slab and not impressed by it’s construction method. On average the polystyrene blocks are 1.0m x 1.0m+ and are put in position, loose on the base of the proposed concrete slab. The required steel trench mesh lays between the polystyrene blocks that will be filled with concrete to form a floor slab.
I have seen polystyrene blocks being “blown over” by the concrete pump machine during laying of the concrete. Once the polystyrene blocks has been “moved” or out of position, the concrete pump keeps pumping concrete to form a floor slab. In that scenario the top of the slab can now be 10mm thick instead of 80 or 100mm thick due to the movement of the polystyrene “fallen over” blocks. This is now an unstable slab!
The Waffle Concrete floor was invented in Germany and it is not suitable for Australian conditions and workmanship. This is the reason that John Gersteling & Associates will not design Waffle slabs and my structural engineer will not certify these type of slabs.
OPINION OF JOHN GERSTELING & ASSOCIATES ONLY
Concrete Floor Slabs
As a guide only (minimum to maximum price range). All pricing is in Australian Dollars (AUD).
|Concrete Floor Slab||Concrete Raft Floor Slab (plan & details) design drawing @ $7.50 per Sq M||$|
|Concrete Waffle Slab||We do not design/draw waffle slabs (Polystyrene is not a construction product)||N/A|
|Structural Steel Portal Frame||(plan & details)||On Application|
|Concrete Suspended Floor Slab||Concrete Suspended Floor Slab (plan & details) @ $ 9.50 per Sq M||$|
|Foundations & Footings||Foundations & Footings (plan & details) @ $ 8.00 per Sq M||$|
|Structural supporting Beams||Structural supporting Beams (plan & details) @ $ 8.00 per Sq M||$|
|Structural Engineering Certification and/or Hard Copies||Structural Engineers Certificate & Specifications||$650|
|Drawing & Document Printing|