The mortar should be a mix based on sharp sand with soft sand added to achieve workability.
Nhbc roofing mortar.
On page 5 specifically addresses mortar placement to verges which nhbc has seen to be susceptible to the effects of freeze thaw action.
In cavity walls over openings air bricks and the like.
Clay bricks contain soluble sulfate s1 designations have no limit on their sulfate content and so a suitable mortar should be used.
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Nhbc is authorised by the prudential regulation authority and regulated by the financial conduct authority and the prudential regulation authority.
Nhbc s registered address is.
Nhbc house davy avenue knowlhill milton keynes bucks mk5 8fp.
A cavity tray should be provided to direct to the outside any water that enters the cavity.
The proportion of sharp sand should not be less than one third of the total sand content proprietary mixes may be accepted by nhbc where they are shown to have similar strength durability and workability.
National house building council is registered in england and wales under company number 320784.
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The cavity tray should fully protect the opening.
150mm above adjoining roof surface to link with the roof upstand.
Chapter 7 2 pitched roofs page 12 s12 b includes the following guidance.
Where traditional mortar pointing is used to bed ridge tiles extend over the ridge continue over hips to form a 150mm minimum lap parallel with the hip rafter at abutments be supported and turned up by a minimum of 100mm be draped to allow water to drain behind the tiling battens.
Wet bedded verge tiles or slates should be fully bedded on roofing mortar having a minimum width of 100mm.
Mortar is vulnerable to deterioration by sulfates especially when masonry is saturated for long periods of time.
National house building council is registered in england and wales under company number 320784.
To reduce risk sulfate resisting portland cement to bs en 197 1 should be used.
Nhbc house davy avenue knowlhill milton keynes bucks mk5 8fp.
Nhbc is authorised by the prudential regulation authority and regulated by the financial conduct authority and the prudential regulation authority.
General wall area above dpc.