Fire Fight!

Preparing yourself and your property. Part Two.

In the first part of this latest thinking on fire I concentrated on what to wear and ended by looking at how flying embers are the main culprit for both spreading fire and by getting into our houses, setting them on fire. In this second part on fire I'll be looking at where those embers can get in and what we can do to stop them.

above: fire risks 1.

• embers can lodge behind barge boards

• under and behind wood trim around door

• under window and door sills

• through gaps between missing, cracked or broken slates

• can ignite an accumulation of leaf litter at base of wall

• plant climbing up to barge board a potential fire ladder

• plastic trim on external light

• windows can crack from radiant heat

• Good points: stone wall, metal gutters and downpipe, close fitting slates (I know, I fixed every one of them...

Preparing and defending our homes.

I'll be using our dwelling at Penrhos to provide examples of what needs to be done to fire-harden a dwelling, as there are plenty of opportunities here! Last time I posted some pictures, each of which presented multiple fire risks. Here I'm including the same pictures with notes on where some of the dangers lie- if you spot more, please let me know!

Its to be hoped that as we go on, low impacters and self-builders will be able to incorporate fire safe building practices and techniques from the start. We also probably need to learn from some careful thought and probably experience, regarding the effects of fire on more unconventional buildings such as round houses, turf roofs and straw bale construction.

The critical vulnerable areas in buildings where embers can lodge or get inside are the roof and ceiling space, windows and doors and the subfloor so we need to design our homes, or retro-fit them to make it difficult for embers to get in here.

This is where David talks extensively of flywire in his Flywire House design. Basically flywire, which seems to be called flymesh in the UK, is a 1mm mesh designed to exclude insects from houses and porches when fitted over doors and windows while allowing air to move through. In fire hardening buildings, the mesh acts to reflect some of the radiant heat of a fire and critically, stops embers from getting inside. For fire prevention, its obviously important to use the metal mesh versions (galvanised or stainless steel) rather than fibreglass or plastic!

Here I'll be pointing to the areas that need attention rather than coming up with all the individual solutions.

above: fire risks 2.

• rough sawn boards can trap embers

• overlaps between boards can trap embers

• open space under floor allows leaf litter to accumulate and sparks/embers can blow in. Close with flymesh panels.

• flammable petroleum products stored under floor- duh!

• temporary door of flammable plastic tarp- duh!

• sheet metal verge piece has gap behind

Roof and ceiling.

The verges (where the roof meets a gable end) and eaves (where a sloping roof meets a wall) are critical entry points for embers as fire can then spread inside the roof. Its also not easy to seal. Barge boards on eaves can be boxed in to the wall but box profile or corrugated metal roofs pose problems as the openings are awkward shapes.

Plastic or fibreglass skylights (as on our sheet metal roof) pose further difficulties as wind blown, burning material that lodges here can melt and burn through the skylight and again, get into the roof space. David suggests fly mesh, metal framed lids that can be put over the skylight but again, tight fitting them to a profiled roof would not be straightforward.

Slate roofs with broken, loose or missing slates offer opportunities for embers to sneak in. Single sheet metal roofs are pretty good but any joins should be tight. Eave closers on profiled roofs are usually of foam and often collect debris so embers lodging here can be dangerous. I also have some concerns regarding the fittings which are usually a screw with a bolt head with a metal washer over a rubber or synthetic washer that acts as a seal. Mine also came with plastic covers the pop over the bolt head. If burning debris collects on or around them, presumably the cover and the seal could melt and burn.

Photovoltaic panels on roofs collect leaf litter and provide places where blown embers can lodge and although cables and conduit or trunking are generally self-extinguishing plastic, they can still melt and in an intense fire and will burn at some point, causing short circuits. In the face of an advancing fire front its probably best to turn panels off. Similarly, bottles of gas would best be turned off, disconnected and put somewhere away from buildings, ideally in a large open area with a hard surface- not always possible.

above: fire risks 3.

• verge unfinished, wooden slate battens showing with space under slate and exposed membrane

• gap behind barge boards and trap embers

• vegetation and debris allowed to accumulate up to wooden members

• gap under sill can trap embers

• cracks in oak lintel over window can trap embers

• ferns growing under ridge tiles will dry out during drought and burn

Turf roofs present a particular challenge as in the sort of drought conditions that make a wildfire likely, its probable that a turf roof will dry out and, if its a living roof, any vegetation may die, leaving a highly combustible surface that is very likely to trap blown embers. The best approach here may be to set aside a water supply specifically to soak the roof surface in the event of a wildfire approaching or embers blowing in and then allotting time in your patrol or a specific person, to maintain vigilance.

Timber walls are generally OK as long as flames do not come into contact with them and I dealt with this in the last piece. With timber cladding, rough sawn boards are more likely to trap embers on the surface than planed and painted boards though pressure treated wood and older paints can give off poisonous gases and smoke as they heat up and if they catch fire. Embers can also lodge between the boards and as the boards heat up they can warp, increasing the gaps between them.

So vigilance during a fire event is vital and for particularly susceptible and crucial structures, it may be worth adding sprinklers running along the top of the wall. David Holmgren's Retrosuburbia has a picture showing a good example of this.

Windows and doors.

Well fitted, draught proofed windows and doors should prevent embers squeezing in but they can lodge on and under window and door sills, particularly if there's already a build up of debris like leaf litter. In the event of a serious wildfire, radiant heat can crack the glass allowing entry of embers so In fire prone sites, David suggests tight fitting, metal framed flymesh shutters which, as well as stopping embers, will reflect some of the radiant heat.

above: fire risks 4.

• photovoltaic panels allow debris to accumulate underneath

• cables and conduit are generally self-extinguishing plastic but can still melt in intense fires

• embers landing on fibre glass roof panel can melt it

• gaps under roof ridge piece can trap debris and are filled with foam inserts

• flashing around stove point has gaps that can trap embers

• caps and seals of roof fixings are plastic/rubber

Subfloor.

If the house is raised on pillars, as is our kitchen extension, then any gaps between walls and the ground should be closed off with framed flymesh which, as well as keeping the embers out in a fire event, will stop leaves collecting there in the first place. I found it tempting to use this space for storage but that's not such a good idea, considering the fire risk.

I'll make a few other more general points. Although tidiness for the sake of tidiness is, as Bill Mollison points out, the sign of a disordered system (i.e. regular work for no product), a certain level of tidiness is good practice when considering wildfire risks. So ensuring that leaf litter and other debris is cleared from gutters and roofs, from around windows, doors and the base of walls is a good idea. Similarly, not having stuff like timber stacked against a flammable wall, particularly if its then covered with a plastic sheet- I know, I've done it.

Gutters and downpipes are best if metal as the plastic stuff will melt and burn. In the event of a wild fire, if you have an easy way to block the downpipes (a tennis ball can sometime be all you need) and then fill the gutters with water- some of the heat of the fire will be expended in boiling off the water before it starts on actual damage. Accumulating containers (baths, tubs, open tanks, ponds etc.) full of water adjacent to buildings means easy access to dip buckets when dealing with spot fires started by flying embers. These can be used for watering plants in normal conditions anyway, as well as being available for fire fighting.

Having a hosepipe and standpipe with sufficient pressure to reach the top of your roof is potentially vital. John Vaillants book, Fireweather, which I've mentioned in a previous piece, talks of one man's courageous efforts to save his house during the Fort MacMurray fire, having sneaked back to it after the compulsory evacuation. Standing on his garage roof with just a hosepipe he was able to save his house twice when the fire swept up to it and then passed him by, by damping down the tarred, shingle roof. Sadly when it switched direction yet again and came back he did accept firefighters' advice and evacuated. His house did burn to ashes but his beloved Harley, which he'd moved into the road, survived unscathed. Such are the vagaries of wildfire.

above: fire risks 5.

• gaps under profiled metal sheets are difficult to fill, allowing embers to blow into the roof space

• exposed breathable roof membrane (green) and heavy duty damp proof membrane (black) in gutter

• moss will dry out in drought and burn in fire

• cables and conduit are self-extinguishing plastic but will still melt and burn in extreme fires

• debris collects on roof below and can be ignited by blown embers

Finally, be prepared, know where the weak points in your property are, have a plan and in the event of a wildfire in your area, be vigilant. This means actively patrolling your site, keeping an eye on smoke, even if it seems distant, observing wind direction and watching for embers being blown in. On your patrol, repeatedly check in particular the key areas where embers can enter buildings and watch out for spot fires. Its important to include the interior of the house or buildings as well in your patrol, just in case an ember gets in and starts smouldering somewhere.

This is by no means a complete account but rather gives a few pointers to key areas that require attention. Much of the preparation for fire is useful practice anyway- getting rid of synthetic materials in home furnishings, for example, stopping draughts, sweeping your flat roof, removing leak litter from the base of walls etc. etc.

I can't recommend enough Joan Webster's excellent books or the relevant chapters of David Holmgren's Retrosuburbia and various articles on his web site¹. If ypou can’t afford them, get your library to order the books, if you still have a library, or buy copies to share between a few of you. The digital editions are very reasonably priced. In our ever warming world they contain information that could save your home or your life.

Thanks for reading. I'm still working on a list of species that are less prone to fire and a list of species to avoid, plus how to fire test species simply and safely for yourself, so that will appear at some point. Next however, given the incessant wet weather here in the UK which at the moment is making wildfire look very unlikely (Phew! More time to get ready), I'll be looking at forest hydrology and in particular, rainfall in our forest environment.

As always and especially with this piece, I would be grateful for any comments, suggestions, pointers and especially, practical experience. Many thanks. Till next time, hwyl! Chris.

1. Joan Webster's The Complete Bushfire Safety Book is the book on bushfire/wildfire. With fifty years of experience its packed with information and also an excellent read. She's the primary source for Australian fire defence and fire fighting and is very highly respected. David Holmgren acknowledges her as a mentor and personal friend. Her Essential Bushfire Safety Tips - 3rd Edition, condenses her work into a highly ordered and accessible series of chapters of bullet points and is available through David Holmgren's website and can be found here.

You can buy a digital copy of David Holmgren's Retrosuburbia direct from his website where he also provides many excellent, free resources.

I have found the following articles by David especially helpful when thinking about wildfire

Bushfire Resilience

Bushfire Resiliant Land and Climate care

The latter article includes a link to a free extract from his Retrosuburbia covering the chapter on Bushfire Resilience which you can aslo access here as a free download.