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Rockwool Cavity Slabs
Rockwool Cavityprovides a completely reliable
and cost effective method of insulating new masonry cavity walls.
The lightweight insulation batts considerably
reduce heat loss without permitting water transmission from the outer to
the inner leaf.
The risk of condensation is also reduced
and intermittent heating systems will be more effective.
Advantages
BBA Agrément certified for all exposure zones
Water repellent
Excellent thermal and fire insulation
Superior fit against blockwork
Construction and installation guidance
The outer leaf is the first line of defence
against rain. Its effectiveness will be improved if attention is paid to
the following points:
The width of the cavity should be designed afterconsideration of the dimensional tolerances
of the components which make up the wall. An
extra 5mm above the nominal batt thickness will normally
be sufficient.
Select porous bricks, which in periods of brief, heavyshowers will absorb the moisture. A non-absorbent
brick will channel water into the mortar joints.
Select a lime mortar mix that does not containdetergent-type plasticisers, which reduce the
water resistance of the joints.
Specify weather-struck, flush or bucket-handle
joints. Recessed joints increase the risk of water penetration. Ensure all
bed joints and perpend joints in the external wall are fully filled with
mortar.
Cavity trays should incorporate stop
ends and have weep holes at approximately
450
mm centres (max 900 mm centres).
Cavity trays
should be continuous across closely spaced openings (Figure 1) and stop ends provided.
Vertical DPCs at wall openings should
project at least
25
mm into the cavity.
(See Rockwool Cavity Closers Data Sheet for details.)
The use of Rockwool
Cavity does not affect the choice of ties to
BS 1243 (or DD140),
which should be selected according to structural
requirements.
Installing Rockwool Cavity
It is the installer’s responsibility to
ensure that Rockwool Cavity is fitted in accordance with the recommendations
of their data sheet.
The installation of the batts should commence below
the DPC (preferably by at least150mm) with no risk of capillary action to
minimise cold bridging. The bottom row of ties should be at 450 mm centres horizontally.
If necessary, the width of the first course of batts can be cut to suit
the height of the next row of wall ties.
The width of cut batts should always be 5 mm greater than the width to be insulated, eg wall tie centres.
It
is recommended that the external leaf be constructed ahead of the internal
leaf so that any mortar protruding into the cavity space from the back of
the external leaf can be cleaned off before installing the batts.
Build up a complete section of the leading leaf to
one course above the next row of wall ties spaced at max. 900 mm horizontally.
Ensure that all mortar joints are properly filled,
particularly the perpends.
Before
installation of each course of batts, excess mortar must be removed from
the inside face of the leading leaf and mortar droppings cleaned from the
exposed edges of the batts. This is made easier by the use of a cavity board. This sequence should be maintained progressively up
to wallplate (or cavity tray) level.
It is important that the insulation
is carried to the highest level possible in either case.
Fit Rockwool Cavity by compressing between the two rows
of wall ties to form a clean and tight butt jointed course. Wall tie drips
should be located centrally in the Batts.
Ties must be inclined downwards
towards the outer leaf. 
It is essential that all joints between Rockwool Cavity
batts are clean and tightly butted. Raise the second leaf to the same level as the batts.The as-built cavity width must not exceed the following
dimensions:
Nominal Batt
thickness (mm) |
Maximum as-built clear
cavity width (mm) |
65 |
75 |
80 |
95 |
90 |
105 |
100 |
115 |
110 |
125 |
Repeat this sequence to the top of the wall. If not, protect the top of
the batts with a cavity tray.
To prevent water penetration to the inner leaf during
driving rain, it is essential that no gaps are left between the batts.
Cut the batts cleanly, using a sharp, long bladed knife
and a straight edge.
Fit the batts closely around wall openings. Slit the
batts neatly where additional wall ties occur. Do not impale or tear them.
At corner joints, edges must be cut accurately to ensure close butting.
Cut the batts accurately to fit between wall ties, if
not conventionally coursed.
Ensure closely butted joints by cutting the
batts 5 mm larger in size than the wall-tie centres. Avoid the build up of mortar on cavity trays.
Where make-up pieces have to be used, ensure that they
are installed with the same direction of grain.
Protect the top of the cavity wall insulation at the
end of the work period with a waterproof covering.
Store or cover Rockwool Cavity not in use and protect
from site damage
External Walls - Masonry Cavity Walls – Full Fill – (Built-in)
Rockwool Cavity is extremely easy to install; cutting is simple (preferably
with a long bladed knife and straight edge). The construction of the batts,
and flexibility along their length and width, allows tight ‘knitted’ joints
to be obtained easily on site.
If a batt requires cutting, its width should always be 5mm greater than
the width to be insulated, eg wall-tie centres, ensuring a tight/closely
butted installation.
The use of Rockwool Cavity does not affect the choice of ties to BS
1243 (or DD140), which should be selected according to structural requirements.
It is the contractor’s responsibility to ensure that Rockwool Cavity is
fitted in accordance with the recommendations on the data sheet for Rockwool
Cavity.
The installation of the batts should commence below the DPC to minimise
cold bridging. The bottom row of ties should be at 450 mm centres. If necessary,
the width of the first course of batts can be cut to suit the height of
the next row of wall ties. The width of cut batts should always be 5 mm
greater than the width to be insulated, eg wall tie centres.
It is recommended that the external leaf be constructed ahead of the
internal leaf so that any mortar protruding into the cavity space from
the back of the external leaf can be cleaned off before installing the
batts. Build up a complete section of the leading leaf to one.
Build up
a complete section of the leading leaf to one course above the next row
of wall ties spaced at max. 900 mm horizontally.
Ensure that all mortar joints are properly filled, particularly the
perpends.
Before installation of each course of batts, excess mortar must be
removed from the inside face of the leading leaf and mortar droppings cleaned
from the exposed edges of the batts. This is made easier by the use of a
cavity board
This sequence should be maintained progressively up to wallplate (or
cavity tray) level. It is important that the insulation is carried to the
highest level possible in either case
Fit Rockwool Cavity by compressing between the two rows of wall ties
to form a clean and tight butt jointed course Wall tie drips should
be located centrally in the batts. Ties must be inclined downwards towards
the outer leaf.
It is essential that all joints between Rockwool Cavity batts are clean
and tightly butted.
Raise the second leaf to the same level as the batts.
The as-built cavity width must not exceed the following dimensions:
Repeat this sequence to the top of the wall. If not, protect the
top of the batts with a cavity tray. Cavity trays should incorporate stop
ends and have weep holes at approximately 450 mm centres. Cavity trays should
be continuous across closely spaced openings.
Nominal Batt
thickness (mm) |
Maximum as-built clear
cavity width (mm) |
50 |
60 |
65 |
75 |
75 |
85 |
80 |
95 |
90 |
105 |
100 |
115 |
Water resistance
Provided the batts are correctly installed and sound
building techniques are applied to the cavity wall construction, any water
penetrating the outer leaf will drain down the surface of the batts. The
direction of the grain of the mineral wool ensures that the insulation will
stop water crossing the cavity to the inner leaf.
Standards and approvals
Rockwool Cavity has been examined by the British
Board of Agrément and granted BBA Certificate 94/3079 for use in all exposure
zones for buildings up to 12 m in height and for buildings over 12 m and
up to 25 m in height in zones where the exposure factor does not exceed
120.
To comply with the requirements of the Agrément Certificate,
and to ensure trouble free performance, the masonry walls must be built
in accordance with BS 5628:Part 3: 1985 or BS 5390: 1976, as appropriate,
and the workmanship on site must comply with BS 8000: Part 3: 1989.
Rockwool Cavity conforms to BS EN 13162:2001 ‘Specification
for factory-made mineral wool products’.
Manufacturer
Rockwool Limited, Pencoed, Bridgend, South Wales, CF35 6NY United Kingdom
Tel: 01656 862621 - Fax: 01656 862302 - Email: info@rockwool.co.uk