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www.RisingDamp.Sydney
Read this description if you want more detail.
Here is a video about what rising damp does to a house and how installing sub floor ventilation can actually speed up the damage to your house dramatically!
Water does NOT damage masonry, salt does. As salt dries in the masonry, as the salt crystals grow, they push apart the bond between the sand and cement particles. THIS is what causes the damage to the masonry.
How does salt water dry?
Evaporation!
What are you doing when you install fans?
Speeding up EVAPORATION dramatically.
What's left over when the water is gone?
Salt Crystals.
To give you an idea of how much force salt crystals have, it can turn 60MPA concrete to dust over time. Your bricks are no where near 60MPA, a standard house slab is around 25-30MPA.
*You may need some kind of ventilation BUT you CAN mitigate the damage that may occur.
You ONLY need sub-floor ventilation for 3 things.
1. Removing damp smells before they come up through your floor boards.
2. Helping to control a mould problem.
3. Helping to prevent the timber under your house from rotting.
If your house is built on clay, by drying the subfloor out too much with fans you can cause the walls of your house to crack. Clay expands when it is wet and contracts when it dries, kind of like breathing lungs.
*** The point of this video is to show that sub-floor ventilation fans DO NOT STOP RISING DAMP. Visit my website to learn more www.RisingDamp.Sydney
Rising damp, mould, damp smells and rotting timber are all very closely related problems caused by moisture under your house but the solutions for each individual problem can be very different.
If you DON'T have a salt issue there then you MAY NOT get damage like this. I have also been to houses that have had fans installed for more than 10 years and they do not have this kind of damage.
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 sand & cement render and apply it to the subfloor walls 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 sand and cement 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 sand & cement layer instead of the bricks.