Eaves, soffits, the big flat bits that protect the walls from rain.
There are a few different risk categories, which depend on the height of the building. Imagine an umbrella if you will. A really big one will stop water from hitting you anywhere. A slightly smaller one will keep you dry above the knees, and a really small purse sized one should keep the rain off your shoulders and head only.
A house with no eaves doesn’t protect the walls at all.
In general terms then, we want some protection for our walls, but different designs of house can offer varying degrees of protection.
Very High Risk:
“0-100mm at first floor or 100 – 450mm at second floor level, or 450 -600mm at third floor level.”
No eaves could be a bargeboard mounted directly on the wall, with the roof ending on top, or it could be a parapet roof edge. We know that no eaves presents a higher risk of water getting in. That risk can generally be managed, with good flashing and roof details, and a good cleaning and maintenance regimen. It starts with keeping the gutters clean enough that water can get away fast
“100 – 450mm at first floor, or 450 – 600mm at second floor level.”
“450 – 600mm at first floor, or over 600mm at second floor level.”
Having a small eave offers a small degree of protection. Small eaves are generally defined as being around 100mm. Risk management is the same as the above.
“Greater than 600mm at first floor level”
These categories are somewhat arbitrary – but does dictate the level of vigilance required in regularly self inspecting, maintaining and repairing the risk areas.
Drop soffits vs flush soffits vs sarked soffits
Drop soffits are lower than the ceiling level inside the house. The good thing about these, if water does get beyond the roof (a common occurence if gutters are allowed to block) then it is still technically outside the building envelope. A challenge with drop soffits will generally be insulating to the edge, and installing extractor ducts which exit via the soffit.
Flush soffits generally mean a taller roof profile – insulation and extractor installation is easier, but if water gets beyond the roofing, it can more easily make its way inside the building envelope.
Sarked soffits sometimes present a challenge if the sarking material has begun to degrade – the only easy way to fix these involves removing the roofing. This can still be a challenge with all types, but sarked soffits are more visible.
Soffit materials vary greatly: Common ones, and quirks are below.
Tongue and groove timber is a common one – Keeping paint in good order can get a bit tricky. Older homes often have slightly shrunken timber, which may well be painted with lead based paints.(Linky!!)
Can contain asbestos, but generally holds paint well, though with age, it does tend to get brittle.
Newer fibre cement doesn’t tend to get quite as brittle as the older stuff can. If the house is newer than 1988 then it is fairly safe to assume the soffits are fibre cement.
Generally one can tell when tempered hardboard is fitted, because it is water resistant, but not waterproof. As such, it tends to suck moisture up and buckle somewhat. It doesn’t neccesarily hold paint as well as the fibre cements do.