Flat roofs, terraces and balconies

7.1.17Parapets and guarding to terraces and balconies

Terraces and balconies to which persons have regular access other than for maintenance, shall be adequately guarded to minimise the risk of falling. Issues to be considered include:

  1. guarding
  2. stability of guarding
  3. strength, movement and weatherproofing of masonry balcony walls
  4. durability and fixing of balustrading and guard rails
  5. access for maintenance.


Guarding should:

  • not be easily climbed by young children
  • be to an adequate height
  • be toughened glass, laminated glass (subject to meeting fire regulations) or glass blocks (suitably reinforced) where glazed balustrading is used
  • not inhibit the flow of drainage on the waterproofing layers or overflows in the event of a blocked outlet

Stability of guarding

Guarding, including parapet walls and balustrading used as guarding, should be designed in accordance with BS EN 1991-1-1 to resist horizontal loading and as required by building regulations. Care is needed when the design incorporates balustrading fixed to parapet walls to ensure stability and prevent overturning. End fixings into walls or returns may be needed to ensure stability.

In balcony walls (especially long balconies) the structural stability should be checked, as cavity trays and DPCs in the wall can create a slip plane that can seriously limit the ability of the wall to resist horizontal forces. In such cases, it may be necessary to incorporate a ring beam or other support to ensure stability.

Strength, movement and weatherproofing of masonry balcony walls

Masonry balcony walls should be built in accordance with Chapter 6.1 ‘External masonry walls. In particular:

  • walls should incorporate strengthening as required by the design.
  • movement joints should be provided in accordance with the design.
  • top of the walls should be weatherproofed with a coping, or by the deck waterproofing layer taken up and over the masonry wall.
  • copings should be firmly fixed.
  • copings should project a minimum 45mm beyond the faces of the wall below and incorporate a drip feature that discharges water at least 30mm away from the face of the wall and stops water running back under the coping. Note: preformed edge trims that are sealed to and form a finished edge to the waterproofing layer and which extend down over the wall/fascia, may have a lesser drip projection provided the waterproofing layer drains away from the trim.
  • copings should incorporate DPC’s and cavity trays linked to the waterproofing layer upstands. Cavity trays should be installed to discharge towards the external face of the wall and incorporate weep holes at maximum 1000mm centres.

Parapet detail with waterproofing taken over top of wall and finished with an edge trim

Durability and fixing of balustrading and guard rails

Balustrading and guard rails should be of adequate durability and fixed securely. The structure to which the balustrading and guard rails are fixed should be adequate to safely resist the potential forces acting on the guarding.

Balustrading should not be:

  • fixed through a coping or capping due to the difficulties in achieving a waterproof junction with the coping or capping and maintaining an imperforate DPC beneath the coping or capping. These issues should be avoided by fixing the balustrading to the face of the wall below the coping or capping.
  • fixed through the waterproofing layer unless suitable precautions are taken to provide a waterproof junction e.g. locating baseplates on a raised waterproofed kerb or surrounded the baseplates in a pitch pocket detail.

Pitch pocket sealing detail around post fixed to deck

Handrail fixing on an upstand formed in concrete roofs

Base of balustrade post raised above drainage level

Balustrade post fixed to wall below coping/kerb

Particular attention should be given to use of materials or finishes that resist corrosion or unsightly surface staining in aggressive environments such as coastal zones.


Ferritic stainless steel can suffer surface rusting/staining in coastal zones.

Access for maintenance

Provision should be made for safe future access to flat roofs for the purposes of maintenance.