External Wall - Masonry Cavity Walls – Partial Fill

Installing HP Partial Fill 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, and the workmanship on site must comply with BS 8000: Part 3: 1989.

Wall ties

The use of HP Partial Fill Slabs does not affect the choice of ties to DD140 (or BS 1243), which should be selected according to structural requirements.

Wall ties should always be inclined downwards towards the outer leaf, bedded in fresh mortar and have the drip part of the tie near the centre of the open cavity. Ties with multi drip can often be positioned centrally and part of the drip will normally be near the centre of the open section of the partially filled cavity.

Construct the cavity wall in accordance with conventional bricklaying practice using the recommendations of BS 5628: Part 3: 1985, BS Code of Practice for use of masonry and BS 5390: 1976 (1984): Code of Practice for stone masonry, and also bearing in mind the design considerations previously stated.
 
Clean off excess mortar from the cavity face of the wall before installing the slab.
 
Do not allow mortar to drop on top of the slabs positioned in the cavity. Protect top of slabs with a batten during installation.
 
Do not allow mortar to drop into the cavity. After each section of the inner leaf is built, excess mortar should be removed from the cavity face and mortar droppings cleaned from exposed edges of the installed board, before installation of the next run of boards. Use of a cavity board is recommended to protect board edges and make cleaning easier. Also, a cavity batten will protect the installed boards and help to keep the cavity clean as the outer leaf is built up.

1) Position the first row of wall ties as near as possible to the damp proof course level. To minimise cold bridging at ground level the HP Partial Fill Cavity Slabs should be installed to extend below the damp proof course ( to reduce thermal bridging at junction with ground floors).
 
2) Build up a section of the inner leaf to one or two block courses above the next row of wall ties (this will normally entail a slight vertical compression of the slabs) and secure with retaining clip.

Note: To obtain the optimum performance of the system, the slabs should be placed with the patterned side outwards.
 
3) If the vertical spacing of the first two rows of wall ties is less than the conventional 450 mm, the slab width (height) should be reduced accordingly. Build the remaining leaf to the level of the top edge of the installed HP Partial Fill Cavity Slabs, ensuring that the desired residual cavity width is achieved.
 
4) Complete successive sections of wall up to the roof line, incorporating Rockwool HP Partial Fill Cavity Slabs and fixings as the work proceeds. It is important to continue the insulation to the highest level of the wall unless the top of the insulation and the cavity are protected by a cavity tray.
The cavity tray may be omitted if the maintained cavity width is at least 50 mm.

Horizontal and vertical DPCs should be fitted at all external openings.Windows at door reveals should also be thermally broken. See Rockwool fire rated cavity closers.

Note: Where cut slabs of less than full length are installed, a minimum of 2 clips should be provided to support the lower edge of the slab.
 
Where additional cavity ties are required for structural reasons, the slabs should be slit neatly to accept the tie. Do not impale or tear the slab.

Standards and approvals

Rockwool Partial Fill Cavity Slabs comply with the requirements of BS EN 13162: 2001 ‘Thermal insulation products for buildings – Factory made mineral wool products - specification’, where appropriate.
 
Rockwool HP Partial Fill Cavity Slabs are fire safe and rated A1 when tested to EN 13501-1 classification using test data from reaction to fire test.
 
CE Mark & Kitemark

Building regulations

Rockwool HP Partial Fill Cavity Slabs satisfy the following requirements of the Building Regulations:
 
Approved Document 'C' (2004 edition)section C2, resistance to moisture The product does not absorb water by capillary action and may therefore be used in situations where it bridges the DPC.
 
Para 5.15 allows Rockwool HP Partial Fill Cavity Slabs to be used to partially fill masonry walls constructed from brick, block or dressed stone.