August_1970 — Page 37

ii. Proposals shall be based on the quantities in the drawings and bills of quantities.

(B) Separate pricing:

i. Maintenance stock. Provide main- tenance stock equal to 11⁄2per cent. of the area of each type of acoustical ceil- ing panel, unit, tile, and plastic cloth and

One per cent of the area of each type of perforated panel, low-frequency ele- ment and fibreglass and rockwool blanket and/or batts.

Etc.

(C) Unit pricing:

$.

i. The contractor shall submit the fol- lowing unit prices, which shall form the basis for any 'addition to' or 'deduction from' the contract. ii. To supply and install

-

Mineral fibre lay-in panels com- plete with all required framing, suspen- sion systems mouldings and accessories including support on the system for light fixtures, A/C diffusers, etc. As covered

cost

in paragraph 10(B)added

work

per sq. ft....

cost deducted work

Special conditions to be followed during construction

1. NOISE CONTROL

In order to achieve the required sound transmission loss in the fabric of

the building as designed, it is impera- tive that no voids, cracks nor weak- nesses be permitted in the construc- tion which would reduce its effective-

ness.

The design of the building fabric enclosing the area listed in this speci-

fication under para. 1 (GENERAL)

has involved the selection of sound

insulating materials for walls, floors, roofs and ceilings to prevent external noise from exceeding acceptable levels within these enclosures. Noise generat- ed by air conditioning equipment, transformers, emergency power gen- erators, switchgear, etc. has been analyzed and controlled to meet de- sign requirements.

The following notes apply to all pro- tected areas:

(A) Concrete. Floor and roof slabs. at the specified areas are each to be cast in one continuous pour. Should concreting be interrupted by incle- ment weather or any other cause be- yond the contractor's control, then when concreting is resumed against a hardened surface, the following pro-

Far East BUILDER, August 1970

cedures shall apply.

The surface shall be bush hammer- ed until the aggregate over the whole surface is exposed. The exposed face shall be cleaned, thoroughly wetted and covered with a thin layer of mor- tar consisting of cement and sand in the same ratio as the cement and sand in the concrete mix. The new concrete shall be well rammed against the exist- ing concrete by hand before resuming

machine vibration.

(B) Masonry. It is essential that all joints in the masonry be completely filled, special attention being paid to vertical jointing.

Horizontal joint reinforcing to be installed every

course in

thick walls and every course in ...... thick walls.

The ends of joint reinforcing to be connected to the abutting structure by wiring, welding or by dovetail inserts.

Wall cross ties between wythes of masonry, concrete walls or structure and masonry wythes to be installed at ft. c.c. horizontally and every course vertically. These ties to be constructed of No. 10 S.W.G. gal- vanized wire in the form of a figure eight. Care to be taken to ensure no build-up of mortar on the wire ties.

Vertical ties to be installed at meet- ing of masonry with roof slab over as in item above.

)

(refer to drawings Nos. ... (C) Mortar. The mortar to be em- ployed for all brick walls within the

areas listed to be as follows:

between the frames and the walls or partitioning is essential.

2. ROOM ACOUSTICS

In order to achieve the correct acoustical environment the design has taken into consideration room shape, dimensions, volume, room proportions and the selection and distribution of

acoustical materials (absorptive and reflective) to satisfy the optimum re- verberation time and the uniform quality of response over the sound spectrum.

The design and the use of materials acoustically is mathematically an ac- curate engineering science but does enfold design assumptions regarding acoustical values of materials. These values are the mean for the particular type of materials, and the installed products vary slightly in acoustical performance, necessitating post con- struction adjustment to meet critical design criteria in the following areas.

This physical adjustment forms part of the building contract and is the responsibility of the main contractor.

The following methods of acoustical adjustment shall be employed. (A) Removable acoustical wall panels:

..)

(Refer drawings Nos. Proportions by volume - Portland

Portland (B) Additions to ceiling system: Cement 1; Hydrated lime or lime put- ty over 4 to 4; Aggregate in damp loose condition 2 to 3 times the volume of cement plus lime.

(D) Openings. It is essential that all

openings in floors, walls and ceilings be neatly cut to within one inch all around service ducts, conduits, pipes, trunking etc. passing through them. The openings to be packed back with oakum, fibreglass or rockwool caulk ing and the edges grouted with cement mortar or trowelling consistency non- hardening caulking depending on location.

―

(E) Doors and windows. These units form the weak links in noise control design and must receive careful atten- tion to achieve their best possible per- formance.

In order to meet their design rat- ings acoustically the frames, saddles, seals and ironmongery installation must be fitted with precision and all the points outlined in drawings Nos...... must be properly followed. Careful packing back of the voids

Etc.

Supervision

(Refer drawings Nos.

.)

In order to achieve a successful

result acoustically, the above section Special conditions to be followed during construction' must be strictly adhered to. This involves all trades and of necessity means strict and close supervision by the architect.

There are many minor problems on any project to be overcome and the best method is to follow a set pro- gramme of review. Control and co- ordination between the main contrac- tor, sub-trades and suppliers is best achieved by a programme schedule covering ordering of materials. con- struction and supervision prepared by the participating parties and aided by the architect in layout and content.

In a number of circumstances the ceiling tile, mineral wool blankets, ac- coustic doors (if required), perforated materials (plywoods, asbestos etc.) will

33