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Guide

Install Formbo's two-layer roofing-felt package

A guided checklist for Formbo's calculated roofing package, with MIDA YEP2200 underlay and MIDA SELF KSK self-adhesive top layer, for gable and pent roofs.

Written by FormboProduct and installation guide
11 min read Updated

Four quick facts about the package

Two named layers

MIDA YEP2200 is the underlay. MIDA SELF KSK is the self-adhesive top layer installed above it.

Calculated for the building

Quantities in LOG-ROOFING-PACKAGE are calculated from the roof of your configured building.

Finishes for both roof types

The guide shows separate finishing sections for gable and pent roofs. Follow the one that matches your building.

Tongue-and-groove timber deck

This guide is for Formbo's planed tongue-and-groove pine roof boards, nominally 22 × 95 mm.

Show the guide contents

Before you begin

Plan all work at height from ground level before installation begins.

  1. Plan the work at height

    Plan access, fall protection, material handling and rescue before anyone goes onto the roof.

    Check first

    • The scaffold, guardrails, openings and segregated area have been checked.
    • The weather, roof surface and access allow the work to be carried out safely.
    1. Decide how materials will be raised without anyone carrying rolls up a ladder.
    2. Review the work sequence and decide who will stop the work if conditions change.

    Ready for the next step when

    Access, protection, material handling and the rescue plan are ready and understood by everyone on site.

    Weather, fall risk and structural uncertainty are stop conditions, not problems to solve while on the roof.

Package and tools

Lay out the roofing components and prepare the tools at ground level before you begin.

  1. Check that everything is present

    Match the delivery to the order and gather the tools before any material is taken onto the roof.

    Check first

    • In the package: MIDA YEP2200 underlay, MIDA SELF KSK top layer, eaves flashing, verge flashing, 45 × 45 mm triangular battens, ALSAN MASTIC 2200 roofing mastic and roofing nails. Screws for the triangular battens are not included.
    • Tools you need: tape measure, straightedge, marking pencil, stable cutting surface, roofing-felt knife, tin snips, pressure roller, hammer, drill/driver and cartridge gun.
    1. Lay out the components somewhere dry at ground level and check them against the order and product labels.
    2. Set aside damaged or unrecognised items. If any items are missing, damaged or unrecognised, contact Formbo before continuing.

    Ready for the next step when

    Every package component is present, undamaged and matches the order. The tools are gathered and ready.

Roof boards and cutting

Inspect the roof boards before they are covered and prepare the cutting work at ground level.

  1. Inspect the roof boards

    Examine the entire tongue-and-groove deck before any part is concealed.

    Check first

    • The roof boards have been installed to the building drawing.
    • The whole surface can be inspected without leaving the approved protected area.
    1. Check that the surface is clean, dry and free from sharp objects.
    2. Look for damage, movement, proud fixings and local unevenness.
    3. Stop and have the deck assessed by a competent person if the structure or load-bearing capacity is uncertain.

    Ready for the next step when

    The complete deck is documented and approved, with no moisture, damage, movement, sharp objects or unresolved changes in level.

  1. Measure and cut at ground level

    Make a cutting list from the approved package drawing and distinguish the narrow starter strip from the full-width underlay sheets.

    Check first

    • The technically approved package drawing is available.
    • A stable cutting surface and a safe method of using the knife are set up at ground level.
    1. Measure the roof slope and compare it with the drawing's joint positions and folds.
    2. Mark the narrow starter strip and each full-width underlay sheet for its position without damaging the surface.
    3. Support the starter strip and full-width sheets while cutting, then keep them separate and protected until installation.

    Ready for the next step when

    The starter strip and first full-width underlay sheet are identified, correctly oriented and checked against the drawing without guessing any installation dimensions.

Build the eaves and protected edges

Bond the starter strip, nail the eaves flashing and screw the triangular battens into the roof boards before laying the full underlay.

  1. Bond the starter strip and nail the eaves flashing

    A narrow strip of MIDA YEP2200 is bonded directly to the roof boards before the eaves flashing is placed over it and nailed in position.

    Check first

    • The roof boards have passed their inspection and are clean and dry.
    • The approved eaves detail defines the positions of the starter strip, roofing mastic and flashing, together with the flashing fixings.
    1. Dry-position a narrow strip of MIDA YEP2200 directly on the roof boards along the eaves.
    2. Apply roofing mastic as shown in the detail and bond the strip without creases.
    3. Dry-position the eaves flashing over the bonded strip and check its direction, corners and joints.
    4. Nail the flashing using the fixing arrangement and sequence shown in the detail.

    Ready for the next step when

    The starter strip lies smoothly against the roof boards and the eaves flashing lies straight, flat and continuous above it.

  1. Screw the triangular battens to the roof boards

    Install the triangular battens directly into the roof boards before laying the full underlay.

    Check first

    • An approved detail is available for this roof type and every affected edge.
    • The triangular battens have been matched to the order and the correct screws are available on site.
    1. Dry-position the triangular battens and check their positions, junctions and corners against the drawing.
    2. Screw the triangular battens directly into the roof boards using the fixing arrangement shown in the detail.
    3. Check that every batten is secure and that no fixing stands proud.

    Ready for the next step when

    The triangular battens are secure directly in the roof boards and ready to be covered by the underlay.

Install MIDA YEP2200 as the underlay

MIDA YEP2200 forms layer 1. It must not be left as the sole finished roof layer.

  1. Align the first full underlay sheet

    Lay the full underlay sheet over the prepared eaves and bring it up and over the triangular battens as shown in the detail.

    Check first

    • The starter strip and eaves flashing are installed and have passed their checkpoint.
    • The triangular battens are screwed directly into the roof boards and have passed their checkpoint.
    • The approved package drawing defines the sheet direction and fixing arrangement.
    1. Dry-position a full sheet of MIDA YEP2200 over the prepared eaves detail and check its line from both roof edges.
    2. Bring the underlay up and over the triangular battens as shown in the detail and smooth the material without stretching it.
    3. Fix only within the zones and with the fixings stated in the approved instructions.

    Ready for the next step when

    The full underlay sheet lies straight, flat and undamaged over the eaves and up and over the triangular battens.

  1. Continue the underlay across the roof

    Position each new sheet to the approved water-shedding sequence and inspect every junction before it is covered.

    Check first

    • The first underlay sheet has passed its checkpoint.
    • The drawing defines side laps, end joints, joint offsets and any sealing requirement.
    1. Dry-position the next sheet and inspect the full lap area.
    2. Clean and dry every surface that will meet.
    3. Close the joint and complete fixing or sealing exactly as instructed.

    Ready for the next step when

    Every lap and end joint is complete, clean, closed and recorded before the next sheet covers the area.

  1. Approve the complete underlay

    Make this a clear hold point before MIDA SELF KSK is taken onto the roof.

    Check first

    • Every layer 1 sheet and detail is complete.
    • Photographs can be taken from a protected working position.
    1. Trace every joint and edge, including areas that will be hard to see later.
    2. Check that the surface lies flat, with no holes, creases or open junctions.
    3. Photograph the complete layer and every end joint before starting layer 2.

    Ready for the next step when

    Layer 1 is complete, flat, documented and approved against the package drawing's hold points.

Install MIDA SELF KSK as the top layer

Layer 2 is self-adhesive. Remove the release film and press the surface only when the sheet is correctly positioned and the underlay meets the approved surface requirements.

  1. Align the first top-layer sheet

    Check the complete position before exposing the adhesive surface.

    Check first

    • The underlay and eaves detail have passed their checkpoints.
    • Temperature, surface conditions, direction and starting position have been verified in the current instructions.
    1. Dry-position the sheet with the release film intact and check it against both edges.
    2. Remove the release film in controlled stages without contaminating the adhesive.
    3. Press the specified area evenly with the correct tool and inspect it at once.

    Ready for the next step when

    The first top-layer sheet is straight and flat, with a clean, evenly pressed bond and no trapped creases.

  1. Complete the top-layer sheets and joints

    Before removing the release film, check how every new top-layer joint relates to the layer 1 joints.

    Check first

    • The first top-layer sheet has passed its checkpoint.
    • The drawing defines laps, end joints, offsets, mastic and any fixing requirement.
    1. Dry-position the next sheet and compare the joints in both layers with the drawing.
    2. Clean the surfaces, expose the release film in stages and make the joint in the stated sequence.
    3. Press the whole joint area and inspect the edge, end joint and connections before continuing.

    Ready for the next step when

    Layer 2 lies flat, every joint is closed, and all joint offsets and seals have been recorded.

Choose the finish for your roof type

Complete only the branch that matches the building: the ridge for a gable roof or the high edge for a pent roof.

  1. Gable roof

    Complete the gable-roof ridge

    Coordinate both roof slopes so the ridge forms one continuous detail.

    Check first

    • The top layer on both roof slopes has passed its checkpoints.
    • A signed Formbo drawing defines the layer sequence, folds, sealing and ridge termination.
    1. Dry-position the material from both roof slopes across the ridge area.
    2. Form the folds, any additional strip, mastic and fixings in the order shown on the drawing.
    3. Inspect the full ridge from both sides before completing the edge flashings.

    Ready for the next step when

    The ridge is continuous, closed and recorded along the full length of the gable roof.

  1. Pent roof

    Complete the high edge of the pent roof

    Verify the pitch before closing the high edge. Roofs below 5° remain blocked until the 3° build-up has signed technical approval.

    Check first

    • The actual roof pitch has been measured and recorded.
    • A signed Formbo drawing defines the high-edge layer sequence, folds, sealing and flashing.
    1. Stop if the roof pitch is below 5° and there is no project-specific signed approval.
    2. Dry-position the membrane and edge components without exposing adhesive surfaces.
    3. Build and inspect the high edge in the sequence shown on the drawing.

    Ready for the next step when

    The pitch is approved and the high edge is continuous, closed and documented.

Inspect and record the finished roof

Finish only after every roof slope, edge and relevant roof-type branch has been checked from a protected working position.

  1. Install the final flashings and inspect the roof

    Close corners and edge flashings to the drawing, then inspect the complete system from the eaves to the ridge or high edge.

    Check first

    • The applicable roof-type branch has passed its checkpoint.
    • Every open corner and edge can be compared with the signed drawing.
    1. Install the final flashings in the stated sequence and inspect every corner.
    2. Trace all joints, edges and water-shedding routes, and remove loose material.
    3. Photograph the roof and retain product names, article numbers, batch details, the drawing and the instructions used.
    4. Plan future checks to the approved product and maintenance information, and after severe weather or visible damage.

    Ready for the next step when

    There are no open joints, damaged areas, loose parts or obstructed water-shedding routes, and the whole installation has been recorded.