<< Previous

Appendix S3: Documentation for a small project

The purpose of this Appendix is to show extracts from the production documents for a small project, sufficient to illustrate the main recommendations of Section 5 of the Code. The project is a two-storey extension to a house, the contract value of the work being approximately £90,000.

Drawings

There were twelve production drawings as follows:

• 2 drawings showing the existing building
• 4 general arrangement plans
• 4 general arrangement sections
• 2 assembly drawings

One general arrangement section is shown on the next page. The specification references on the drawing were copied and pasted from the schedule of work construction headings.

Schedule of work

A contents list for the schedule of work is given here, arranged by elements (although the work is to an existing building it is a principally a new extension rather than alteration work).

The two 'constructions' for roof coverings are reproduced in full.

Reference specification

Section H62 of the reference specification is given in full.

Drawing

The specification references on the drawing were copied and pasted from the schedule of work 'construction' headings. (Note: the drawing will open in another window).

Schedule of work contents

Example constructions

Reference specification

Produced from a basic text by editing out material that does not apply to the project, e.g. hips, valleys, vertical slating, snowguards, etc.

H62 NATURAL SLATING

PRODUCTS

Slates
Natural slates: To BS 680–2.
Minimum width: The greater of half the length or 150 mm.

Battens and counterbattens
Timber: Permissible characteristics and defects limits: To BS 5534–1.
Type: Sawn softwood, species type A (imported Whitewood, Redwood, Canadian/ USA Spruce/ Pine/ Fir or USA Southern Pine) or B (British grown Corsican Pine, Scots Pine or Sitka Spruce).
Moisture content at time of fixing (maximum): 22%.

Fixings for slates
Copper clout nails: To BS 1202–2.
Size: 3.35 mm shank diameter. Length to provide adequate withdrawal resistance and at least 15 mm penetration into battens.

EXECUTION

Slating generally
Fix slate roofing to make the whole sound and weathertight at the earliest opportunity.
Setting out: To true lines and regular appearance, with neat fit at edges, junctions and features.
Gutters and pipes: Keep free of debris. Clean out at completion.

Existing natural slating
Alterations: Minimize the amount of slates, battens and underlay removed. Minimize disturbance of adjacent slates.

Underlay
Do not tear or puncture.
Maintain consistent tautness when laid.
At penetrations: Use a proprietary underlay seal. Cut accurately and turn flanges up to give a tight, watershedding fit.
Ventilation paths: Do not obstruct.

Batten fixing
Setting out: In straight horizontal lines. Align on adjacent areas.
Batten length (minimum): 1200 mm.
Joints: Square cut, butt centrally on supports. Joints must not occur more than once in any group of four battens on any one support.
Unsupported underlay laps between battens: Provide additional battens.
Fix each batten to each support. Splay fix at joints.

Slate fixing
Setting out: Align tails. Lay with an even overall appearance, with slightly open (maximum 5 mm) butt joints.
Headlaps and sidelaps (minimum): To BS 5534–1to suit slate size, roof pitch and exposure.
Thickness: Consistent in any one course. Lay with thicker end as tail.
Ends of courses: Maintain bond. Provide extra wide slates as necessary.
Top course: Head-nail short course to maintain gauge.
Cut slates to be as large as possible.
Fixing: Two nails to each slate. Centre fix through countersunk holes 20-25 mm from side edges.

Mortar bedding and pointing
Do not use in wet or frosty weather or when such weather is imminent.
Concrete and clay tile accessories to be bedded: Wet and allow water to drain off before fixing.
Finish neatly as work proceeds. Remove residue.

Edges, junctions and features
Cut slates only where necessary, to give neat, close fitting joints and straight, clean edges.
Fix edge slates and fittings securely to neat, true lines.
Flashings: Fix with or immediately after the slating. Dress down neatly.

Eaves
Grilles and/ or ventilator trays: Fix between supports to provide free passage of air over insulation.
Underlay: Prevent water retaining troughs. Dress underlay or underlay carrier down into gutter.
Eaves slates: Fix with tails projecting 50 mm over gutter or to centre line of gutter, whichever dimension is less.

Mortar bedded verges
Slating battens: Carry over undercloak and finish 100 mm from verge edge.
Verge slates: Bed edge flush with undercloak on 75 mm wide bed of mortar. Do not displace or crack mortar.
Verges with bedded undercloak: Carry underlay 50 mm onto outer leaf of gable wall and bed in mortar.
Undercloak slates: Bed in mortar identical to that used in gable walling. Position level with underside of slating battens. Slope away from wall. Project 38-50 mm beyond face of wall.

Abutments
Side abutments: Turn underlay 100 mm (minimum) up abutment. Cut slates as necessary, interleave with soakers. Fix soakers by turning down over the head of each slate. Fix slates close to abutment. Form a weathertight junction with step flashing.
Top edge abutments: Turn underlay 100 mm (minimum) up abutment. Finish slating with a head-nailed short course, maintaining headlap. Fix slates close to abutment. Form a weathertight junction with an apron flashing.

Roof windows
Turn up underlay 100 mm (minimum) against window surround. Cover with integral flashing/ soakers all round. Cut slates as necessary. Fix closely all round.

Ridges
Finish slating with head-nailed short course, maintaining headlap.
Lay underlay from one side of ridge over apex to overlap top course of underlay at other side by 150 mm (minimum).
Mortar bedded tile ridges: Bedding to be continuous along edges and solid at joints. Finish joints neatly and flush.

<< Previous