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General Advice When Laying a GRP Roof

Repairing a GRP roof
Advice when using GRP during Winter months
Advice when using GRP during Summer months
Safe working practices

Repairing a GRP roof

If the roof surface becomes damaged by impact or has to be cut for any reason it can be easily repaired using the following procedure:

  1. Clean off the damaged area with solvent and abrade the GRP surface with a hand grinder for a distance of 100mm from the damaged area or edge to be joined.
  2. Cut the 450/600gm2 glass to the correct size to cover the affected area and mix sufficient resin with catalyst as previously described.
  3. Brush resin onto the area to be laminated at the rate of 1 kilo per square metre.
    Place the glass over the area, wet out the glass with resin at the rate of 0.5 kilos per square metre. Stipple well with the brush or use a paddle wheel roller for larger areas.
  4. Ensure that the laminate is free from air and completely consolidated and allow to cure.
  5. Mix the Topcoat with catalyst as previously described and apply with a brush at the rate of 0.5 kilos per square metre.
  6. Allow to cure.

This procedure will ensure that the patch or joining piece applied will bond to the original laminate and form a weatherproof patch over the damaged or cut laminate.

Advice when using GRP during Winter months

Always check the local weather forecast (See Commercial Manual for details on how to obtain an accurate forecast).

During the Winter, avoid topcoating a roof after 2-3pm unless it is a clear bright day and not too cold. The heat from the sun contributes a great deal towards the curing of the laminate during colder months. After the sun has set, it is unlikely that the topcoat will cure over night. If left uncured, the topcoat may cure with debris and leaves stuck to the surface, or with an undesirable finish if it rains.

Ensure that the surface temperature of the boards is checked before laying the resin or topcoat. Ensure that the resin is warmed before use if the ambient temperature is below 10ºC.

Always ensure that the resin remains indoors the night before it is used. Do not use resin or topcoat in temperatures below 5ºC.

If it begins to rain, cover the roof with a visqueen sheet.

If you are unable to laminate over a prepared deck, then coat the decking with catalysed resin and cover any exposed edges. This will seal the deck and prevent moisture uptake until the laminate can be applied.

Always cover the edges of the roof and uncoated boards with a polyethylene sheet.

Always ensure the deck or substrate to be laid onto is completely dry before laying the laminate. Sweep off any excess water and mop up the excess with dry cloths before allowing the roof to dry naturally.

Wiping the surface with acetone can speed up this process.

Do not start to lay a roof if a period of rain is forecast.

Advice when using GRP during Summer months

Always check the local weather forecast (See Commercial Manual for details on how to get an accurate forecast online and useful telephone numbers).

Do not use roofing resin or topcoat in temperatures above 35oC.

Always mix smaller batches of resin then you normally would to give adequate time to apply it before it starts to catalyse. Always use LPT catalyst in hotter weather if the resin starts to cure too quickly.

Always apply the laminate in the shortest runs possible across a roof. The shorter the length of laminate, the less likely it is that the resin will catalyse before it can be consolidated into the laminate.

Use a temperature sensore to measure the surface temperature of the laminate before applying the topcoat. If topcoat is applied to surfaces above 50oC, the wax component of the topcoat will melt and the topcoat will remain tacky to the touch, this will usually mean that any loose debris will stick to the roof and the colour of the topcoat will also be impaired.

If possible, topcoat the roof out of direct sunlight or wait until later in the day before applying it, it may mean that the roof will take you longer but it will save you time spent returning to the roof to re-topcoat it at a later date.

Safe working practices

It is always the installer's responsibility to ensure safe working practices for themselves and their employees and always pay attention to the risks for other members of the public that may be nearby at the time. The following notes are designed to help you ensure a safe working environment, but they are by no means comprehensive and any installers should always assess any potential risks when working on a contract and make sufficient means to address them. In addition to these notes, the installer should also be aware of the health and safety information that applies to most materials (see Health and Safety Manual).


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