Mixing Resin and Topcoat
Calculating resin and top coat
Firstly you will probably have already have noticed I refer to everything in Litres and square Meters, if you have read other fibreglassing sites you may have noticed they work in weight ( Kilos ). I work in Litres as its easier to Estimate and to explain amounts and coverage.
Roof Resin and Topcoat Weight
You can expect if purchasing a 20 Kilo keg or drum for it to contain about 18 to 19 Litres. I have also listed average CSM chopped stand mat weight even though it is sold in meters and weight.
How much roof resin per meter square of matting
Lets assume your using 450g ( 1.5oz ) chopped strand mat, if you allow 2 litres of resin per square meter you should find it easy to work with and gives a good dry spot and pin hole free coverage. So a 10m2 roof @ 1 layer would require 20L of resin.
- 300g CSM – 1.5L resin per m2
- 450g CSM – 2L resin per m2
- 600g CSM – 2.5L resin per m2
In warm temperature or with thinner grade roofing resin you may get a better wet out and need slightly less resin than quoted.
How much Topcoat per meter square
If the weather is warm the topcoat will be thinner and easier to spread, expect to work at about 1L of topcoat for every 2 – 3 m2. In cold weather the topcoat becomes thicker and doesn’t flow as easily so allow 1L per 2 meters square.
Resin storage
If the weather is very hot make sure you keep resin and topcoat in the shade at all times, likewise in very cold conditions it may pay to bring resins or topcoats into a gently heated environment the evening before any usage. Remember the resin is the lifeblood of your new roof, don’t abuse it.
Mixing fiberglass Roof Resin
Always wear a full wrap around eye protection.
I like to use a 15L roller bucket marked inside in litres, or on small jobs a 5L paint scuttle again marked internally. Always measure the temperature of the roof decking before mixing any resin, and on a hot day keep all resins and topcoats in the shade.
Simply mix in the normal manner by measuring out the desired catalyst and poring it onto the resin, but be careful as the catalyst can sit on the surface and be quite splashy until it gets under the top surface of the resin.
When adding Catalyst my preference is to use a 60 or 100ml syringe for adding catalyst as it injects the hardener underneath the surface of the resin or topcoat. This way it mixes faster and there is less splashing if the catalyst sits on top of the resin, as it normally does when you use a standard catalyst tool.
Never use less than 1% or more than 3 – 4% catalyst with resin and mix thoroughly.
Draw up the exact amount of required catalyst and inject it in a figure of eight motion from about 6 ” away (150mm ) the force of the stream will penetrate the surface of the resin easily.
See Catalyst chart further down
Your fibreglass supplier should send you either summer or winter catalyst depending on the time of year but you will have to specify if you need LPT for hot weather.
Mixing fiberglass roofing resin or topcoat
Temperature and weather are the arch enemy’s of the fiberglasser but lets deal with weather first.
Rain : Do not fibreglass if its going to like rain, or you think it may rain. Fibreglass hates rain which is good when the roof is complete but your absolute worst nightmare with matting on the roof, exposed roof decking or halfway through applying the resin. If it rains on you at this stage you may have to have a little cry.
Fog or damp : This may coat you decking or roofing trims with moisture and cause de lamination.
Temperature : Obviously the weather will play a big role in this and please study the Catalyst and resin drying and curing times provided below. Temperature does not only mean ambient air temperature but the temperature of the decking and the resin itself as these will affect the curing times greatly. A laser thermometer is a great tool for measuring roof deck and resin temperature.
Very Cold weather : Below 5C and down to 0c and just below , there are now several cold cure resins on the market for working in these temperature ranges but bear in mind fog or damp associated with cold weather can cause delamination. You can also possibly use a reaction accelerator like ’ accelerator G ‘ with normal resin.
Cold weather : 5C to 15C use a normal fast Catalyst or winter Catalyst, you can also possibly use a reaction accelerator like ’ accelerator G ‘ with normal resin.
Good weather : 15C to 28C standard Catalyst or summer Catalyst
Hot weather : 26C – 36C Ideally use LPT ( Long Process Time ) Catalyst or slow Catalyst and keep resins and topcoats cool before use. Top surface may stay tacky for 48 hours or more in temperatures above 28C, this can be an issue for working on the surface or debris and insects sticking to it.
Roofing Resin and Hardener Cure times
Always try to use any resin or topcoat within the first 3 – 6 months of purchase, don’t stock pile old fibreglass resins. Curing times may become unreliable as might the performance of the resin itself, try to keep it fresh. Do not use catalyst if its over 1 year old.
Please feel use the chart below as a guide to curing times for roof resins and top coats
Catalyst Temperature & Ratio Chart
Roofing resin and topcoat curing and hardening times complete with suggested ratios for different temperatures.
Click to enlarge
Applying Topcoat
Standard flat roofing top coat normally comes in grey, often 2 but sometimes 3 shades. It is slightly thinner and a little bit more elastic than a normal coloured polyester flowcoat for fast wet out of the roof surface. A full range of colours are available however.
Make sure you apply the top coat in a generous manner but not more than 1mm in depth, to thin and you can get pin holes and it becomes difficult to apply. Too thick and you risk cracking of the top coat at 2mm or above.
Coverage will be between 2 – 3 square meters per Litre of Top coat.
As long as you are topcoating within 24 hours you will not need to sand the fibreglass laminate you have just laid, however you may have little snags you may wish to sand first with 60 to 80 grit abrasive paper. Do not tread dirt or other contaminants onto you nice clean roof, if you do however clean gently with Acetone and a clean cloth.
Your fibreglass supplier should send you either summer or winter catalyst depending on the time of year but you will have to specify if you need LPT for hot weather.
Fibreglass and Grey topcoat seem to be the most popular choices with my customers, either the light grey topcoat which gives a look of old seasoned lead, or the dark grey topcoat that resembles new bossed lead.
Never use less than 2% Catalyst or more than 4% with Top Coat and mix thoroughly.
A full range of colours are available.
Cold cure resin and topcoat
There are now several cold weather resins and topcoats available, some of the coldest days can also be dry so fibreglassing is still feasible. Manufacturers and suppliers have traditionally always been cautious about what to recommend with fiberglass, quite rightly they would much rather over specify and play it safe. However as fibreglass roofing becomes more mainstream the marketing opportunity that is cold weather or winter resin has lured them out into the cold.
Cold weather fibreglass resin can make on hell of a difference in colder climates or during winter months. See below for cold cure resin drying times.
Normal fibre glass resin will cure in cold conditions but very slowly, possibly many days which makes it impossible to work with unless dry heat is applied form either a electric hot air blower or infra red heat lamp.
Fibreglass in cold weather – cold weather resin cure times
What drying time can I expect with winter resin?
When fibreglassing in cold weather, at 00 C ( 32 degrees Fahrenheit ) and using 3% winter Catalyst using a cold cure resin, somewhere between 45min to an hour out of direct sunlight.
Obviously this will depend on wind chill, heat from below, sunlight and cold cure fibreglass resin manufacturer, but the drying times stated are about correct for branded cold cures and home made cold cure resin.
How to make cold cure resin or winter resin – ( low temperature resin )
Firstly use whatever brand of standard roofing resin you prefer…
Pour out as much resin as you want to work with in the normal manner and add some ‘ accelerator G ‘- The normal ratio is between 0.5 and 2% but check your suppliers instructions. Now add this to the resin but keep your catalyst well away for the moment. Stir in the accelerator thoroughly.
The chances are you resin will already have an accelerator in so use as little accelerator as possible to get the reaction you require, you will be accelerating an already accelerated resin. Obviously I do not know your supplier or their resin so I cannot sate figures.
Only now can you add the Catalyst, this should be you normal fast catalyst or winter grade catalyst. You may notice that the mixture bubbling and in an exited state, I allow this reaction to calm for 5 minutes before applying to decking and CSM. You should get 20-30 minutes of usable working time depending on temperature and ratios, very comparable to off the shelf cold cure resins.
Warning!
Never put catalyst in before accelerator G and never mix catalyst and accelerator G together.
Doing so can lead to combustion, fires or chemical explosion.
Always do a small pot test first and apply to bandages or small test areas, remember your standard resin will probably already have a small amount of accelerant in.
And that’s how to make your own cold cure resin… Ideal for small jobs or fibreglass roof repairs in cold weather. Making your own cold cure winter resin is cheap and easy but it will void and resin guarantees if you are bothered about such things.
This guide can also be used to make cold cure topcoat ( low temperature topcoat )
For low cost high quality fibreglass roofing materials – East Coast Fibre Glass Supplies
Also see…
- How to Fibreglass a Roof
- How to Fibreglass a Bay Roof
- How to Lay the Fiberglass Laminate
- How to Fit Fibreglass Roof Trims
- Fibreglass Problems and FAQ’s
