Over the years, the construction methods regarding rising damp have changed. With new ways of attempting to prevent the rise of dampness from footings and surrounding sub-foundations which are generally comprised of clay, there has also been an increase in the use of chemical injection systems. These systems have gained in popularity due to the inherent belief that plastic is non-absorptive. We believe that the injection system, whilst being beneficial in certain circumstances, can not be looked at as the single and best remedy. We will now break down the reasoning behind why both silicone and polyurethane inject systems that are utilised to counter rising damp are liable to not work.
As a result of drilling at regular intervals, the chemical injection systems use the basis that the brick will ‘absorb’ and disperse the silicone or polyurethane injection applied to try to prevent rising damp. Not only does this depend on the contractor, how well they drill and how much injectable they use, the nominal absorption of various brick will vary due to composition, age and even colour. Concrete blocks, natural stone and clay brick all have differing absorption rates. You can see from the photo above, the ‘cover-up’ bandaid approach does not work with the mortar being soft and still falling out despite the attempt to mask the symptoms of rising damp.
2. Plastic attracts moisture
So you’ve thought to inject silicone or a polyurethane into the masonry fabric of your building. Did you know that once you have injected plastic into what is otherwise a very porous and freely evaporative masonry matrix, you are actually going to harbour moisture in the bricks located in the injected region?! We have found that this will deteriorate your brick faster and often doesn’t stop the moisture tracking its way through both the mortar joint and the masonry unit.
3. Slowing of the Moisture Cycle
The mere fact that you have injected plastics into what was previously a very breathable and porous masonry structure, you are increasing the moisture retention in those areas.
Test it for yourself; If you saturate two clay bricks in water, coat one in cling wrap and not the other, and then place both into the sun, which do you think will dry quicker?
Of course, the brick with plastic will not dry at all. By eliminating the porosity and the rate of evaporation, you are hastening the corrosion caused by being constantly waterlogged…
Silicone and Polyurethane chemical injection systems are somewhat useful in thickened masonry walls with optimal thickness of around 300-400mm. This is due to the physical difficulty of retrofitting a physical barrier in order to prevent rising damp. To install a physical barrier at this depth is very slow going and is generally quite expensive due to it being labour intensive. But this does not mean that you shouldn’t spend the extra money to do something properly! It is against the basic principles of economics to pay a little for a lot… be aware of the quick fix that is cheap!
Chemical injection systems utilised on single skin brick cladding should not be used! Even on double brick structures which are generally only just over 200mm in thickness with a cavity or empty void in between… The mind boggles on how some contractors would think that this would work!
Physical barriers such as lead and slate were used in traditional damp coursing. These methods were very successful at preventing rising damp. Both materials were largely long-serving due to their individual material impermeability characteristics. They prevented the physical movement of moisture up the wall whilst maintaining their physical state.
Modern equivalents are generally reinforced polyurethane and other flashing material. These are just as effective and require less financial outlay than utilising lead and slate. The main benefit beside stopping the vertical movement of moisture is allowing the masonry to evaporate. This enables the brick, block and stone to remain as dry as possible which is the goal in trying to prevent dampness and the odours associated with saturated masonry.
Despite the thousands of dollars spent, the previous owner didn’t stop rising damp nor did they prevent the other aspect of moisture sub-footing conditions, subsidence. Underpinning is also a follow-on issue with rising damp.
By spending more, and being wise in your choice of contractor, you will receive more… Throwing good money after bad is never beneficial. Fix rising damp once and for all with melbournebrickrepair.com. The Physical Damp Course Specialist.