Joints
Board joints are not waterproofing. They are detailed so that water behind them can drain to the membrane.
VlamShield WEER · Weather-resistant mineral board for edges and details
Mineral where
the roof is exposed.
WEER is a glass-fibre-reinforced, cement-bound mineral board for surfaces exposed to weather, water and mechanical stress outside the membrane: upstands, roof edges, penetrations and zones with heavy maintenance traffic. The board protects these details mechanically with a homogeneous mineral material.
01 · Function
Function and installed position
On a PV roof, problems do not concentrate in the open field but at the edges. That is where the membrane turns up, where cable trays and inverters sit, where people walk, climb and set tools down during maintenance. It is also where the roof meets the façade and adjoining elements.
WEER places a weather-resistant mineral board in front of these vulnerable surfaces. The board is intended for external use, takes mechanical stress and keeps the surface of the detail free of combustible material. It is not waterproofing: water that gets behind or below the board must be shed by the membrane and be able to drain away through the detail.
Schematic representation. Not a construction drawing; the actual build-up and detailing follow from the project.
What loads act here?
Weather and frost
Rain, UV and freeze-thaw cycles act directly on the material. That is why a board with documented external use is the starting point.
Impact and maintenance
Ladders, tools, cable trays and foot traffic load edges and upstands harder than the field of the roof.
Adjacent combustible surfaces
At the roof edge, insulation, membrane and sometimes façade materials meet. A mineral board as outer layer limits the combustible surface at the detail; the assessment of the building element follows from the associated evidence.
02 · Material
Material build-up
The reference for WEER is a board of the Aestuver BSP type: cement-bound, glass-fibre-reinforced lightweight concrete with a smooth light-grey face and a fine-pored, homogeneous cut edge. No paper liners, no foam, no coarse gravel.
- Cement-bound lightweight concrete with glass-fibre reinforcement throughout the board
- Homogeneous material: the cut edge is as mineral as the face
- Reference board documented for external use (use category X)
- Available in several thicknesses; specified per detail
03 · Installation
Installation on the roof
- 01
Survey the detail
Height of the upstand, position of the membrane termination, penetrations and fixing options are measured on site.
- 02
Cut boards to size
Sawing with dust extraction, straight edges, cut-outs for penetrations and fixings defined in advance.
- 03
Fix without piercing the waterproofing
Mechanical fixing to the rising structure or a subframe, with open or sealed joints according to the detail drawing. Never through the water-carrying layer without a sealed penetration.
- 04
Finish joints and edges
Joints deliberately remain water-shedding; end faces and bottom edges keep clear of standing water.
- 05
Check drainage
No board may obstruct an outlet, emergency overflow or gravel guard. That check is part of handing over the detail.
Joints, outlets and upstands
Outlets and overflows
Around outlets and overflows the flow remains completely free; boards stop short.
Upstands and roof edges
The board covers the rising face above the membrane termination and finishes under the edge trim or capping.
04 · Data
Technical data
Reference values from manufacturer documentation
Values for the reference board Aestuver BSP according to the product data sheet and ETA-11/0458 (version 6 November 2025). They apply to that make. We quote fire resistance in minutes only for a specific tested building element, never for the board on its own.
| Material | Cement-bound, glass-fibre-reinforced lightweight concrete |
|---|---|
| Thickness and surface mass | From 10 mm · 10 mm ≈ 10 kg/m² |
| Reaction to fire (EN 13501-1) | A1, as stated for the reference board |
| Application | Use category X: external, exposed, according to the ETA |
| Edge | Homogeneous, fine-pored; sawn with dust extraction |
Defined per project
These points are set out in the project proposal, with detail drawing and documents.
| Thickness and format | Per detail, depending on span, fixing and loading |
|---|---|
| Fixing | Mechanical to structure or subframe; joints open or sealed per detail |
| Drainage | No obstruction of outlets and overflows; demonstrated in the detail drawing |
| Evidence | Classification and ETA of the board; assessment of the detail as a building element named separately |
Source: Aestuver fire protection boards (product overview) · Product data sheet Aestuver BSP
05 · Selection
When yes, when no
Suitable
- Upstands, roof edges and penetrations on PV roofs
- Zones with inverters, cable trays and heavy maintenance traffic
- Exposed surfaces where a homogeneous mineral finish is wanted
- Renovation of details without replacing the membrane in the field
Not suitable
- As a waterproof layer or replacement for the membrane
- As a flat cover board below the membrane: that is DEK
- As a support for PV systems without its own system assessment
- Where joints must be watertight: a board does not deliver that
06 · Questions
Questions from practice
Is WEER waterproof?
No. The board is weather-resistant, not waterproof. Joints and junctions shed water to the membrane, which remains the waterproofing.
Can WEER serve as a walkway or PV support?
Not without its own system assessment. A board for external use is not an automatic release for horizontal PV supports or intensive foot traffic.
What fire resistance does the board have?
Fire resistance in minutes belongs to a tested building element, not to a single material. The reference board is documented as A1; which element performance applies to your detail follows from the corresponding assessment.
What about frost?
The reference board is documented for use category X (external). At the detail itself, standing water and wrongly oriented joints remain the biggest risk; that is why we fix drainage in the detail drawing.
Project enquiry for VlamShield WEER
What we need for a quotation
With this information we prepare a concrete proposal: configuration, quantity, documentation and programme. If something is missing, we ask.
Project enquiry- Photos and dimensions of upstands, edges and penetrations
- Type of membrane and height of the termination
- Fixing options: concrete, steel, timber subframe
- Linear metres and required board height
- Any requirements for the building element (fire resistance, façade junction)
