NBS M20 - Dryvit One Coat RenderSystemCAWS
NBS Specification
Common Arrangement of Work Section (CAWS):
M20 Rendered Coatings
Dryvit One Coat Render
Dryvit UK Ltd.
Unit 4 Wren Park
Hitchin Road
Shefford
Bedfordshire
SG17 5JD
Tel: 01462 819555
Fax: 01462 819556
email:
M20 DRYVIT ONE COAT RENDER
To be read with Preliminaries/ General conditions.
TYPES OF COATING
M20/160BSILICONE POLYMER MODIFIED ONE COAT RENDER SYSTEM
-Substrate: [e.g. Existing /new brick masonry wall or blockwork].
-Preparation: [Surface shall be prepared as per manufacturer’s instructions. Poorly keyed surfaces or substrates of uneven or high suction should be prepared with Dryvit Primax].
-Manufacturer: Dryvit UK Ltd, Unit 4 Wren Park, Hitchin Road, Shefford, Beds, SG17 5JD Tel: 01462 819555; Fax: 01462 819556; Web: ; email: ].
-System: Dryvit One Coat, [minimum 18mm thick installed to manufacturer’s instructions]
-First Pass:
-Product reference: Dryvit One Coat
-Thickness (excluding dubbing out and keys): [6-8]mm.
-Second Pass:
-Product reference: Dryvit One Coat
-Thickness: [12-10]mm.
-Finish: texture as manufacturer’s instructions
Colour: [From Dryvit Standard Range].
-Accessories:[To Dryvit recommendation:
- Dryvit Detail Mesh applied diagonally to corners of openings between passes.
- Dryvit Standard Mesh reinforcement applied between passes for added crack resistance where required, please consult Dryvit UK Ltd. for guidance.
- External corner beads.
- Expansion joints to align with structural movement joints (through or surface, and to align with structural movement joints.
- Feature beads – rustication, flash gap or other architectural features.
See Clause M20 632A & 640A].
-Other requirements: [Co-ordinate the Work with interfacing building elements
- Electrical fittings by others.
- Mechanical Services by others.
- Access equipment bracket penetrations by others.
- Windows by others.
- Doors by others].
.
GENERAL
M20/413SAMPLES
-General: Provide representative samples of the following: ______.
M20/418CONTROL SAMPLES
-Complete sample areas, being part of the finished work, in locations as follows: ______.
M20/421SCAFFOLDING
-General: Prevent putlog holes and other breaks in coatings.
M20/424SPECIAL PROTECTION OF HISTORIC PLASTERWORK
-General: Prevent damage and disturbance to retained plasterwork.
-Protection methods: Submit proposals.
MATERIALS AND MAKING OF MORTAR
M20/430READY-TO-USE CEMENT GAUGED MORTARS
-Time and temperature limitations: Use within limits prescribed by mortar manufacturer.
-Re-tempering: Restore workability with water only within prescribed time limits.
M20/497COLD WEATHER
-General: Do not use frozen materials or apply coatings on frozen or frost bound substrates.
-External work: Avoid when air temperature is at or below 5°C and falling or below 3°C and rising. Maintain temperature of work above freezing until coatings have fully hardened.
-Internal work: Take precautions to enable internal coating work to proceed without detriment when air temperature is below 3°C.
PREPARING SUBSTRATES
M20/510SUITABILITY OF SUBSTRATES
-Soundness: Free from loose areas and significant cracks and gaps.
-Cutting, chasing, making good, fixing of conduits and services outlets and the like: Completed.
-Tolerances: Permitting specified flatness/ regularity of finished coatings.
-Cleanliness: Free from dirt, dust, efflorescence and mould, and other contaminants incompatible with coatings.
M20/527RAKING OUT FOR KEY
-Joints in existing masonry: Rake out to a depth of 13 mm (minimum).
-Dust and debris: Remove from joints.
M20/531ROUGHENING FOR KEY
-Substrates: Roughen thoroughly and evenly (where required).
-Depth of surface removal: Minimum necessary to provide an effective key.
M20/M20/541BONDING AGENT APPLICATION
-General: Apply evenly to substrate to achieve effective bond of plaster/ render coat. Protect adjacent surfaces.
M20/549M20/REMOVAL AND RENEWAL OF EXISTING PLASTER/ RENDER
-Location and extent: Agree, at least on a provisional basis, before work commences. Minimize extent of removal and renewal.
M20/556REMOVING DEFECTIVE EXISTING RENDER
-Render for removal: Detached, hollow, soft, friable, badly cracked, affected by efflorescence or otherwise damaged.
-Removing defective render: Cut out to regular rectangular areas with straight edges.
-Horizontal and vertical edges: Square cut or slightly undercut.
-Bottom edges to external render: Do not undercut.
-Render with imitation joints: Cut back to joint lines.
-Cracks:
-Fine hairline cracking/ crazing: Leave.
-Other cracks: ______.
-Dust and loose material: Remove from exposed substrates and edges.
M20/566REMOVING DEFECTIVE EXISTING PLASTER
-Plaster for removal: Detached, soft, friable, badly cracked, affected by efflorescence or otherwise damaged.
-Hollow, detached areas: ______.
-Stained plaster: ______.
-Removing defective plaster. Cut back to a square, sound edge.
-Faults in substrate (structural deficiencies, damp, etc.): Submit proposals.
-Cracks:
-Fine hairline cracking/ crazing: Leave.
-Other cracks: ______.
-Dust and loose material: Remove from exposed substrates and edges.
M20/568EXISTING DAMP AFFECTED PLASTER/ RENDER
-Plaster affected by rising damp: Remove to a height of 300 mm above highest point reached by damp or 1 m above dpc, whichever is higher.
-Perished and salt contaminated masonry:
-Mortar joints: Rake out.
-Masonry units: Submit proposals.
-Faults in substrate (structural deficiencies, additional sources of damp, etc.): Submit proposals.
-Drying out substrates: Established drying conditions. Leave walls to dry for as long as possible before plastering.
-Dust and loose material: Remove from exposed substrates and edges.
M20/592CONSOLIDATING EXISTING TIMBER LATH AND PLASTER CEILINGS
-General: Achieve effective consolidation of plasterwork to supporting structure.
-Methods: ______.
BACKINGS/ BEADS/ JOINTS
M20/630BEADS/ STOPS FOR INTERNAL USE
-Material: Galvanized steel to BS EN 13658-1.
M20/632A BEADS/STOPS FOR EXTERNAL OR INTERNAL USE:
Material: [e.g. PVC or Stainless Steel].
Manufacturer: [Dryvit UK Ltd].
M20/640ABEADS/STOPS GENERALLY:
-Provide beads/stops at all external angles and stop ends except where specified otherwise.
-Cut neatly, form mitres at return angles and remove sharp edges, swarf and other potentially dangerous projections.
-Fix securely, using the longest possible lengths, plumb, square and true to line and level, ensuring full contact of wings with background. Use mechanical fixings for external beads/stops [or Dryvit Adhesive].
-After coatings have been applied, remove coating material while still wet from surfaces of beads/stops which are to be exposed to view.
M20/650ACONSTRUCTION/MOVEMENT JOINTS: Form joints accurately to detail and in locations shown on the [Design]. Drawings. If modifications to any joint location or design are necessary on site, agree revisions with Architect/CA before proceeding. Movements joints shall be incorporated where:
- Expansion joints occur in the substrate system.
- Building expansion joints occur.
- As necessitated by Dryvit One Coat.
M20/651ASEALANT JOINTS:
-Location(s): [insert as applicable].
-Sealant: [insert as applicable].
-Form in accordance with section Z12 and system manufacturer's recommendations using any necessary joint fillers, backing strips, etc.
M20/655A[CONDUITS should be chased into wall sufficiently to give a minimum of 5mm re-profiling coat cover.
OR
- CONDUITS should be surface mounted].
EXTERNAL RENDERING
M20/810APPLICATION GENERALLY
-Application of coatings: Firmly and in one continuous operation between angles and joints. Achieve good adhesion.
-Appearance of finished surfaces: Even and consistent. Free from rippling, hollows, ridges, cracks and crazing.
-Accuracy: Finish to a true plane, to correct line and level, with angles and corners to a right angle unless specified otherwise, and with walls and reveals plumb and square.
-Drying: Prevent excessively rapid or localized drying out.
M20/810AGENERAL APPLICATION
GENERAL REQUIREMENTS:
-Application of coatings: Firmly and in one continuous operation between angles and joints. Achieve good adhesion.
-Appearance of finished surfaces: Even and consistent. Free from rippling, hollows, ridges, cracks and crazing.
-Accuracy: Finish to a true plane, to correct line and level, with angles and corners to a right angle unless specified otherwise, and with walls and reveals plumb and square.
-Drying: Prevent excessively rapid or localized drying out.
-INSTALLATION: The coating shall be applied to Dryvit written instructions by Dryvit trained applicators.
-INSPECTION OF COMPLETED INSTALLATION: As soon as possible after completion of the work and before removing scaffolding, carry out an inspection with the CA to identify any defects.
M20/880ACURING AND DRYING
-General: Prevent premature setting and uneven drying of each coat. Work in the shade and out of drying winds whenever possible
-Drying: Allow each coat to dry thoroughly, with drying shrinkage substantially complete before applying next coat.
-Protection: Protect from frost and rain.
This common arrangement of work section document should be adapted to meet specific project requirements. Clauses should always be modified with the aid of the relevant Dryvit system & product literature and in line with current NBS work section criteria. The completed document can then be included in the overall project specification and be read in conjunction with the Preliminaries/General conditions according to the NBS guidelines.
M20 – DryvitOne Coat RenderSystemCAWSRevision 2 03/2015 / M20/1 of 5 / Dryvit UK Ltd. Ref: DUK 631
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