Module 3 PART 3 - Measurement of Foundations 2 Concrete, Brickwork and Waterproofing PDF

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QUANTITY SURVEYING 1 QSU150S / QSU100S / QSU110X 2018 MODULE 3 PART 3 Measurement of Foundations 2 Concrete, Brickwork and Waterproofing MEASUREMENT OF CONCRETE [Concrete, Formwork & Reinforcement S/S clauses 1 & 2 pg. 24] Concrete is classified according to grade or ...

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QUANTITY SURVEYING 1 QSU150S / QSU100S / QSU110X 2018 MODULE 3 PART 3 Measurement of Foundations 2 Concrete, Brickwork and Waterproofing

MEASUREMENT OF CONCRETE [Concrete, Formwork & Reinforcement S/S clauses 1 & 2 pg. 24] Concrete is classified according to grade or mix. There are basically three types of concrete namely;  Unreinforced concrete (sometimes still referred to as mass concrete).  Reinforced concrete.  Concrete encasing structural steelwork. Concrete can be further described by either mix or strength. Refer to the “Model Preambles for Trades” [D. concrete, formwork and reinforcement MPT clause D.1 5.5.1.6 and 5.5.1.7 pg. 7] Example of mix concrete: 1:4:8 (1 part cement: 4 parts fine aggregate (sand): 8 parts coarse aggregate (stone) – (referred to as Class A concrete). Example of strength concrete: 30 Mpa / 19mm (specified strength followed by the size of the stone to be used in its manufacture). Concrete is measured in m3. Separate items must be given for each different component such as footings, bases and surface beds. Concrete is simply a combination of cement, sand, stone and water in varying amounts. It requires some form of temporary formwork or mould to give it a particular shape or form until such time as it has hardened and gained its own strength. Concrete gains strength through the chemical process occurring between the constituents when water is added. Concrete only gains its full strength 28 days after casting. As mentioned above, formwork is required to the sides of the concrete and will be measured as a separate item from the concrete in m2. However, where concrete is to be cast in excavations and the ground is suitably firm, the sides of the excavations can be used to act as the “formwork”. The “Standard System” requires that where concrete components are to be cast against excavated surfaces; this fact must be stated in the description. Furthermore, the descriptions are “deemed” to include filling to irregularities. This is to allow for any additional small amounts of concrete required and caused by any unevenness that might occur in the sides of the excavations resulting from the removal of any roots and boulders, small rocks, etc. [C, F & R S/S clause 2 pg. 24] Example: “Unreinforced concrete 15 Mpa / 19mm stone in footings cast against excavated surfaces”.

MEASUREMENT OF FOUNDATION BRICKWORK The Masonry trade in the “Standard System” is divided into 7 distinct sections:  General  Brickwork  Block work  Paving, etc.  Rubble walling  Stonework  Miscellaneous For now, we will only concern ourselves with the first two sections: Brickwork is classified according to 3 things: [Masonry S/S clause 1 pg. 34]  The material and quality of the masonry unit.  The bond.  Composition of the mortar. Clay bricks can generally be classified as one of the following: NFP – Non Facing Plastered - suitable for general building work which is to be plastered. NFX – Non Faxing Extra - suitable for general building work in damp situations such as below ground and damp proof course level where appearance is relatively unimportant. E – Engineering grade - bricks required for structural or load bearing purposes where engineer requires a specified strength. FBS – Face Brick Standard - face bricks that are durable, uniform in size and shape. FBX – Face Brick Extra - face bricks possessing highest degree of shape, size and colour uniformity. FBA – Face Brick Aesthetic - bricks selected or produced for a highly individual aesthetic look. Apart from standard bricks (often also referred to as “stone bricks”, “roks” (run of kiln) or “commons”) all having a standard size of 110mm x 75mm x 220mm long, one also get maxibricks, etc. BOND There are a variety of different bonds that are used. The most common being “Stretcher” bond and “English” bond. (other bonds are “Flemish” bond, “English garden wall” bond, “Monk” bond, “Dutch” bond, “rat-trap” bond, “silver locks” bond, etc.) The “Model Preambles for Trades” states wherever practicable, brickwork will be built in “Stretcher” bond. [F. Masonry MPT clause F.10 pg. 12]

MORTAR It goes on further to state that brickwork shall, (unless otherwise described), be built in class II mortar. Class II mortar is defined in the “Model Preambles” as being a 1:6 mortar (1 part cement: 6 parts sand i.e. 50kg cement (1 pocket): 200 litres sand. [F. Masonry MPT clause F.8 pg. 12] The “Standard System” states that walls will be given in m2. Walls are usually described by their thickness, different types of walls being kept separate, such as:  110mm wall (also referred to as “half brick” wall)  230mm wall (also referred to as “one brick wall)  330mm wall (also referred to as a one-and-a-half-brick wall)  280mm cavity wall The skins of hollow walls shall not be measured separately but the overall thickness of the individual skins shall be stated. The descriptions of hollow (cavity) walls shall include wall tiles. [Masonry S/S clause 5.5 pg. 35] The “Model Preambles” states that the wire ties shall be galvanized steel wire and that “Butterfly” type ties are to be used for hollow walls. [F. Masonry MPT clause F.6 pg. 11] It goes on further to state that “hollow” walls shall be built of two half brick skins with a cavity between, tied together with at least 5 wire ties per m2. [F. Masonry MPT clause F.10 pg. 12] As mentioned previously, “Foundations” are measured provisionally. To distinguish between brickwork in foundations (measured provisionally) and brickwork in the superstructure (everything above surface bed and which is not re-measured), we only make mention of this fact in the descriptions of foundations brickwork that these are walls in “foundations” such as shown below: Examples: “110mm wall in “foundations” built in NFP bricks in stretcher bond in class II cement mortar “230mm wall in “foundations” built in NFP bricks in English bond in class II cement mortar It is not necessary to state that brickwork is in the superstructure. It is automatically assumed that all brickwork is in the superstructure unless otherwise described as specifically being “in foundations”. When measuring foundation brickwork, we measure from the top of the concrete footing to the top of surface bed level (T.S.B). Brickwork in walls and linings is always measured in m2. Since the backfilling to the entire trench will have already been measured, (as described elsewhere in these notes) it is also obvious that the brickwork in the trenches occupies a certain volume of this backfilling, and so we must again make an adjustment to the backfilling to “surface trenches”.

NOTE: Brickwork in foundations is measured in m2 (being the length of the wall x height of the brickwork from top of footing to top of surface bed level) BUT backfilling is measured in m3. It should also be noted that backfilling to “surface trenches” is only measured to natural ground level (or to level after topsoil has been removed), whereas, the brickwork goes higher than this level (all the way up to top of surface bed level). For this reason, we cannot measure the brickwork and make the adjustment to the backfilling and generate the material available item simultaneously, as we did when measuring the concrete in footings. One would measure the brickwork as a separate item m2 (Length of brickwork x height of brickwork from top of footing to top of surface bed) m2. Then measure the following two items simultaneously: Deduct Backfilling to surface trenches as before described (m3) AND Add Material available for use as filling below solid floors, etc. (Length of brickwork x overall thickness of wall x height from top of footing up to ngl or level after stripping topsoil)

m3

Concrete filling to hollow walls in foundations [Masonry S/S clause 2 pg. 34] Concrete in filling cavity of hollow walls in foundations is usually a relatively weak unreinforced concrete and is measured as a separate item in m3. Example: “Unreinforced concrete 10 Mpa / 19mm stone in filling cavity of hollow wall including formed splayed top to receive step down in damp proof course” DAMP PROOF COURSE: [Waterproofing S/S clause 1.1 pg. 46] Damp proof course on walls is measured in m2. No distinction is made between horizontal and vertical damp proof course on walls, below sills, around doors and windows, etc. In other words, it is all grouped together as one item called “damp proof course on walls”. The “Model Preambles for Trades” [G. Waterproofing MPT clause G.3 pg. 14] States: “all joints in damp proof course to walls shall be lapped a minimum of 150mm except at junctions and corners where the lap shall equal the full thickness of the wall”.

We make no allowance in our actual measurements for the additional material required at end and side laps, i.e. it is measured net as follows: “375 micron SANS approved damp proof course on walls including all necessary end laps (measured net)” m2 Where a damp proof course is required on a half brick (110mm) or one brick wall (220mm), it is measured in m2 and calculated by taking the length of the wall x thickness of the wall. The damp proof course on 280mm cavity walls usually steps down one course from inner skin to outer skin. The width is thus not simply 280mm. it needs to be calculated. The sloping length in the cavity is 50mm, the height is one course of brickwork 85mm (75mm brick plus 10mm mortar joint). Therefore, the sloping height is given by: √502 + 852 Thus, the total width is 2 / 110 + 98.6

=98.6 = 318.6 rounded up to 319mm

Thus, the measurement of the damp proof course on a 280mm cavity wall would be given by the length of the wall x 0.32 (m2) [no allowance being made for any laps in the length]. MEASUREMENT OF FLOOR CONSTRUCTION Floors can be divided into two distinct types, namely;  

Solid floors. Suspended timber floors.

(concrete floors to multi storey building are referred to as “Slabs” and are included with measurement of the structural concrete work – dealt with in 3rd year). For now, we will only concern ourselves with the measurement of solid floor construction. We will return later in the course to consider the measurement of suspended timber floors, once you have dealt with this type of construction in Construction Technology. Solid Floors Solid floors can be further sub-divided into:  

Floor construction Floor finishes – different types of floor covering such as carpets, floor tiles, vinyl sheeting, etc. Depending on the type of floor finish required, different thickness of cement screed will also be required. The cement screeds and various types of floor finishes (as well as skirtings, etc.) will all be dealt with later and are measured under the section called “Internal finishes”.

Floor construction When measuring the solid floor construction, we begin our measurement from the bottom and work our way upwards to the actual surface bed. Depending on the required level of the surface bed, (as designed by the architect) we may have to either excavate to reduce levels. OR Make use of filling to make up the required levels (more commonly encountered). Solid floor construction comprises the following:  Filling in making up levels.  Sand bed layer to receive the damp proof course.  Damp proof membrane.  Concrete surface bed. (depending on the particular ground conditions, the concrete bed may require some form of reinforcement) (where required, mesh reinforcement is generally used – but this will be determined by the engineer). In order to be able to measure the floor construction, you will require more certain levels to be given, these are: Average Natural Ground Level (NGL) of the site. AND EITHER Finished Floor Level (FFL) OR Level at the top of the concrete surface bed (T.S.B) The first calculation necessary is to establish the amount of “filling” that will be required. Since we are not concerned with the measuring of floor finishes at this stage, we want to know the level at the top of the surface bed (t.s.b.).

Filling below floors

[Earthworks S/S clause 13 pg. 14]

Filling of soil shall be measured to the volume after compaction and be given in m3 stating the method and degree of compaction. Separate items shall be given for backfilling to surface trenches, backfilling to holes and “filling under floors”. Separate items shall be given for “filling” obtained from:   

The excavations Specified borrow pits Supplied by the contractor

The description of filling obtained from the excavations shall be deemed to include for haulage not exceeding 100mm from where it has been excavated (if hauled beyond this distance, then the approximate distance shall be stated). The “Model Preambles for Trades” describes how the filling ought to be done on site. Since the tenderer has been referred to the “Model Preambles”, it is not necessary to state all of this in the actual “bill of quantities” description or our measurement. The “Model Preambles for Trades” (2008) describes how filling below solid floors should be executed (C.3.1 – filling generally). “filling over site shall be spread, leveled watered and consolidated in layers not exceeding 300mm” “Filling under floors shall be suitably inert (stable) material, free from clay, vegetable matter (sticks, roots, twigs, etc.) large stones, etc. spread, leveled and compacted to a density of 90% Modified AASHTO” (American Association of State Highway Traffic Officials). Where the material arising from the excavations is unsuitable for use as filling (such as clay), then the contractor would have to obtain suitable filling from elsewhere and cart it onto the site. A typical description for this would then be: “filling below solid floors with suitable material purchased / obtained by the contractor and carted onto site, placed and compacted as specified” m3 Sand bed

[Earthworks S/S clause 13 pg. 14]

The measurement of the sand bed would also be covered by clause 14. A typical description would be: “50mm thick clean builders sand bed carted onto site, spread and leveled below solid floors to receive damp proof membrane (damp proof membrane elsewhere measured)” m3 The reason we state that the damp proof membrane is elsewhere measured is that once the “bill of quantities” is compiled, the damp proof membrane item will be in the “waterproofing” trade, whilst the sand bed will be in a different trade (“earthworks”). So when the tenderer is calculating his rate for the sand bed, he is informed that he does not have to include cot of the damp proof membrane here. As he will have an opportunity to price for it when he calculates his rates for his items in the “waterproofing” trade. Damp proof membrane

[Waterproofing S/S clause 3 pg. 46]

Waterproofing shall be given in m2 separating waterproofing to floors, roofs, balconies, etc. waterproofing in turn-ups not exceeding 300mm shall be included in general areas. The

“Standard System – Waterproofing” trade makes no mention here of making allowance for any end or side laps. We can however turn to the guidelines provided under the “GENERAL INSTRUCTIONS” of the “standard system” clause 5 page 1 (net measurements) where we find: “unless otherwise described, all work shall be measured net as fixed in position… no allowance shall be made for waste, nor passings and laps….. where laps occur, they shall be included in the descriptions” The descriptions of the damp proof membrane should also indicate the quality or thickness required. Thickness is given not in milimetres but in “microns”. A typical description would be: “275 Micron SANS approved quality under surface bed damp proof membrane laid on sand bed (sand bed elsewhere measured) including all necessary 150mm wide taped side and or end laps (measured net)”.

m2

It is important to remember that the damp proof membrane (dpm) turns up the full thickness of the concrete surface bed against all walls and should also be taped to the dpc on the walls, thereby providing a continuous impervious layer and preventing any rising damp in the superstructure brickwork above floor level. The area of these “turn ups” is not given in the bill of quantities as a separate item, but the area needs to be measured and the total area of the turn ups (m2) must then be added to the horizontal area below the solid floors to obtain the correct total m2 area to insert in the bill of quantities. Concrete surface bed

[Concrete, Formwork & Reinf S/S clause 2.1 pg. 24]

As mentioned in the notes on concrete footings, concrete is separated into reinforced and unreinforced concrete. Separate items are given for different components, such as “surface beds”. A typical description would be: “Unreinforced concrete 15 Mpa/19mm stone in surface beds” m3 Sometimes, one might find that the internal non load bearing walls (i.e. half brick or 110mm walls) will not have their own concrete footings, but will simply be built off the concrete surface bed. Where this is to be done, it will be necessary to thicken out the surface bed sufficiently to carry the load of the wall. The National Building Regulations require footings to have a minimum thickness of 200mm. so where wall is to be built off the concrete surface bed (100mm thick), it will be necessary to thicken out the surface bed by an additional 100mm thickness (i.e. so that the

portion of concrete surface bed below internal non load bearing walls is at least 200mm thick. It is usual to thicken out the surface bed for a width equivalent to the minimum required width of a footing as stated in the National Building Regulations. The concrete in the thickening out of the surface bed is not given as a separate item in the bill of quantities but does need to be separately calculated and should then be added to the volume of the concrete measured for the surface beds. The volume of the additional concrete in the “thickening out” of the concrete surface bed as shown above would be calculated by taking the total length of the thickening (length of the non-load bearing wall) x average width (700mm + 500mm / 2 = 600mm) x additional thickness (100mm). This thickening out of the concrete below non-load bearing walls will impact on the earth filling below and thereafter, an additional item should be measured to compensate the contractor for the additional work in preparing for the thickening out. This item is measured in linear metres (m). “Leave or prepare earth filling to receive thickening out of surface bed 700mm wide extreme x 100mm deep including any necessary adjustment to sand bed and damp proof membrane below as required” m Methodology we follow when measuring solid floor construction. The floors are cast within the foundation walls. The earth filling, sand bed, damp proof membrane and concrete surface bed therefore all have the same horizontal area (m2). It is only the thickness of each of these different items that varies. Since all these items share the same common area, we can measure the whole floor construction simultaneously by inserting the dimensions for the area in the “dim” columns and then “cubing” the various items by their different thickness as shown below:

Filling below solid floors with material arising from the excavation and compacting as specified. Cube x (thickness) = __________ m3 Area for various rooms given in m2

AND

50mm thick clean builder's sand bed to receive dam proof membrane (dpm elsewhere mentioned). Cube x 0.05 = __________m2 AND 275Micron SANS approved damp proof membrane laid on sand bed (sand bed elsewhere measured) including all necessary taped side and end laps. AND Unreinforced concrete 15 Mpa / 19mm stone in surface beds. Cube x 0.10 = ___________m3

List of reference ASAQS (The Association of South African Quantity Surveyors). 2015. Standard System of Measuring Building Work, 7th ed. (ISBN 978-0-86886-837-0) ASAQS (The Association of South African Quantity Surveyors). 1999. Standard System of Measuring Building Work, 6th ed. (Revised) (ISBN 1-919921-03-6) ASAQS (The Association of South African Quantity Surveyors). 2008. Model Preambles of Trades (ISBN 978-0-620-1663-4) Ramsay D (nd) Stu...