Incorrect ventilation. Too high, which is why all the bottom bricks and footings were damaged. The damp was going up as far as the ventilation. It should be at ground level. The whole idea is to have the air flow go across the ground, not 1-1.5m from the floor.

Hi Graham, www.risingdamp.sydney

You can put a mortar or render on the surface of the bricks to act as a sacrificial layer. Fans don't always damage the bricks but it's a good idea if you install them to check the bricks under your house once a year for deterioration. If you see any deterioration you can apply some mortar or render to those areas at 5mm in thickness. It will need to be topped up from time to time if the salt damages the render you apply.

He doesn’t know

You can get it tested, it's the accumulation over time that causes damage. There may be a lower salt percentage in the soil but very porous bricks which absorb and homogenise moisutre faster therefore they get damaged faster. On the other hand you could have high salt content and very dense bricks that have a slower absorption rate which means a lower amount of damage from salt accumulation. It's not so black and white.

Thank you mate,

People can call me for the options, that is the point. ;)

The fans do the same thing regardless of the way they activate. Sometimes you do need fans.. but installing fans for the purpose of curing rising damp is not the solution. Fans are used to eliminate damp smells, mould and rotting timber. Fans do not cure rising damp. Check out my website www.risingdamp.sydney

Yeah if you have termites then you may need some kind of ventilation. If you don't have a salt issue there then you may not get damage like this. If you do need to install fans then keep an eye on the subfloor walls to see if you have any damage occur. If there is damage occurring over time you can get some LIME MORTAR and apply it to the subfloor walls as if it was render with your hands (not real pretty but no one will see it) and the render (you can just use pre-mix sand and cement from your local hardware store) will be a sacrificial layer on the surface sub-floor walls and piers. i.e. The lime mortar "render" will incur the damage instead of your bricks and mortar. By putting a mortar layer ON TOP OF the subfloor walls and piers (as a 5-10mm coating) the salts will crystallise in the NEW layer you have ADDED instead of in the original substrate of your house. Over time this layer may deteriorate and you may need to reapply in places. Doing this will mean you don't get any structural damage as seen in the video above because the salt is damaging the lime mortar layer instead of the bricks.

The damp course was installed about 100mm below internal floor level as per regulation, so below the internal floor didn't have a damp course. If the bricks are in wet ground.. they get wet.. then the brick above gets wet too.. then the brick above that one... with the moisture from the ground comes diluted minerals.. if you dry the masonry, more water comes from below to replace the evaporated water and so on.. speed the evaporation up and you in increase the water coming up the bricks from the soil. Increased evaporation means more water passing through the wall to the evaporation point which means a greater accumulation of salt in the masonry. The salt turns to crystals as it dries and push apart the bonds between the sand and cement, and turns it back to dust. Go and look under 30-40 old houses.. you'll see near vents, sub floor fan exit points or access doors etc that the mortar is more likely to be missing there. This video is an extreme case, the worst I've seen.

@@jasehere4589 interesting mate thanks for explaining. Does it then also depend on salinity of soil? I guess its fair to say some areas would contain more salt? I was contemplating potentially installing some fans. I suppose fans dont dry out the ground enough either to stop or reduce the rising damp

@@united3689 within about 15-20kms of the sea the salt is higher. You only need fans if you have damp smells, rotting timber or mould. Fans just evaporate the water below floor level which makes it look like it's fixed but it's not. Rising damp is about salt, water and evaporation. It's OK of masonry is wet (in the right locations) water doesn't damage masonry, drying salt does. If you have masonry which is being damaged under the house then you can put 5mm of a sacrificial layer off lime mortar on it which will save the walls and piers. Sometimes fans are needed, i try and avoid them when i can. Having said that we installed 3 this week. It's situational.

@@jasehere4589 Thanks Mate. Is that means passive vents are enough and safer than electrical fans for the subfloor?

@@jasehere4589 did u instal eco fans around $250 for a. Pair or just a $30 exhaust fan will do the. Job. My house is wet timber rotted snd I found termite outside near the house beside the house the timber gate . I’m getting t a termite treatment soon as soon as my subfloors dry .. I’m thinking of adding fan and as the guy in video mentioned on comments let it extract air not blow it in