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Definitions
1.1NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
In this Technical Booklet the following definitions apply – Contaminant – is defined in regulation 25 in Part C of the Building Regulations. Drain – is defined in regulation 2 in Part A of the Buildin
drainageprotection-from-fallingmoisturecoastalDPM placement and vapour control layer requirements
5.8NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Where the DPM is on the warm side of the insulation it will also act as a vapour control layer (VCL) and prevent interstitial condensation forming on any of the layers on the cold side of the insulati
drainagemoistureInsulant compressive strength and water absorption
5.9NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Insulants should have sufficient compressive strength to resist the weight of the slab, the anticipated floor loading as well as any possible overloading during construction. In order to resist degrad
drainagemoisturestructuralTimber floor finish and timber fillets treatment
5.10NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
A timber floor finish laid directly on concrete may be bedded in a material which may also serve as a DPM. Timber fillets laid in the concrete as a fixing for a floor finish should be treated with an
drainagemoistureSuspended timber ground floors – general requirements
5.12NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Any suspended timber floor next to the ground should meet the requirement to resist the passage of moisture from the ground if – (a) the ground is covered so as to resist moisture and prevent plant gr
drainagemoistureSuspended timber ground floor construction details
5.13NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
A suspended timber floor next to the ground should be constructed as follows (see Diagram 5.2) – (a) ground cover – (i) unreinforced concrete at least 100 mm thick to mix ST 1 in BS 8500-1. The concre
drainagemoistureCavity trays on raft foundations and ground beams
6.8NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Where a cavity wall is constructed directly off a raft foundation, ground beam or similar supporting structure a cavity tray should be provided with weep holes every 900 mm to assist in the transfer o
moisturedrainagedwellingnon-domesticExternal solid walls
6.9NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
An external solid wall should meet the requirement if it will hold precipitation until it can be released in a dry period without penetrating to the inside of the building, or causing damage to the bu
moistureexternal-spacedwellingnon-domesticInsulated external walls - examples
Diagram 6.4NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Solid walls: external protective system with 50 mm minimum residual cavity, breather membrane, sheathing board, vented and drained cavity. Cavity walls: (a) External insulation, (b) Internal insulatio
dwellingnon-domesticinsulationexternal-wallsmoisturecondensationDamp proof courses at obstructions and openings
6.32NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Damp proof courses should be provided to direct moisture towards the outside – (a) where the downward flow of moisture would be interrupted at an obstruction, e.g. at a lintel (see Diagram 6.3(b)); (b
dwellingnon-domesticprotection-from-fallingglazingmoistureDoor thresholds in external walls - weather protection guidance
6.33NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Guidance on weather protection of accessible thresholds is given in – (a) BRE Good Building Guide 47 Level external thresholds: reducing moisture penetration and thermal bridging; and (b) The Statione
dwellingnon-domesticaccessaccessibilitymoistureStandards and guidance for resisting moisture from weather in roof and wall coverings
7.8NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
The requirement to resist the passage of moisture from the weather can also be met by following the relevant recommendations of – (a) BS CP 143 for sheet roof and wall coverings made from the followin
weather-resistancemoistureroofingcladdingexternal-envelopeInterstitial condensation - scope
8.1, 8.2NI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
Regulation 29 (Condensation) applies only to dwellings. A dwelling should meet the requirement to avoid any harmful effects caused by interstitial condensation if it is designed and constructed in acc
dwellingcondensationmoistureBritish Standards Referenced in Technical Booklet C
Appendix Publications referred toNI-wide·Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture
British Standards (BS) BS EN 998-2: 2003 Specification for mortar for masonry. Masonry mortar. BS EN 13914-1:2005 Design, preparation and application of external rendering and internal plastering. Ext
drainagemoisturesite-planningaccessibility