Air vents around house

its called the Holland damp proof course, its a scam and doesn't work, what you want is someone who understand older properties and how the materials they were constructed with all work to keep them dry and have done for years, modern materials and old houses do not work as they are both trying to achieve different things. Hollands tubes are usually cemented into place creating dampness, cement is a sealer it sucks in moisture, lime mortar is a breather it expels moisture, read the rising damp myth on the internet, or the heritage property site to better understand the materials your house was built with and how they work, the biggest issue is getting someone who can use them properly as todays tradesmen are trained in modern materials and methods & who do untold damage to old house through sheer ignorance rather than malice of what they are doing, take of the tyrolean let the house breathe and if you want to render use N.H.L it can be bought in different colours if you don't want to paint it with lime wash but this is more a spring summer job as the outside temperatures is just a bit to low at the moment. good luck Alex

Alex pretty much covers it .

ADR is correct in his assessment. Older properties were built with timber windows that were draughty, coal fires that kept them warm. Ventilation was never an issue as the warm air from the fire circulated throughout the property. With the draughty windows and doors condensation build up was never an issue. Todays modern materials suffocate the property, Upvc ,terylene , cement mortar etc. the Holland system was initially devised to deal with condensation that was misdiagnosed as damp. It’s both aesthetically unpleasant to look at and more importantly it does not really work. It just allows more moist air to enter the property and condensate when coming in contact with the warm air inside the property. Ideally you require someone who is a certified surveyor of structural waterproofing, who can survey your property to deal with any relevant issues. Also get a tradesman who has experience in working on older properties with both a combination of modern and older materials. Modern materials are generally ok to use internally, but it’s imperative that any exposed brickwork is treated correctly with antisulphate to neutralise any salts within the old mortar and brick or stonework. This would be prior to any rendering works.

Ventilation systems will not prevent either rising or penetrative damp within solid wall construction, and are primarily fitted within any building to facilitate air flow helping to prevent condensation and potential moulding. 1920’s buildings are solid wall construction, ie there is no cavity, and sometimes would have been traditionally fitted with air bricks systems for air flow, relying on bitumen dpc’s to prevent rising damp. It’s important to say that there’s a difference in the purpose of air bricks for venting suspended timber floors and those located in walls above floor level. I’ve neither fitted or come across the system you’ve described but can only reiterate that should your damp problem relate to either rising damp or penetrative damp , no ventilation system can remedy these problems. I would expect that in your 1920’s property the original bitumen damp course would have degenerated , and unless the property has either had a chemical injection , silicon rod dpc system installed , or cement based tanking system, then there is a strong possibility of some rising damp. Since 1988 I have worked in conjunction with one of the regions leading damp and remedial work experts , that complete full surveys, providing a schedule and specification for the works . These works we carry out together to the specialist design specification , with the customer benefitting from full certified , accredited and insured remedial works. This is also financially viable as the specialist fees for survey, schedule, and certification is very competitive, usually my part, is the larger part of the job , and in simple terms I am able to provide that service at a more competitive rate than if the specialist was completing all the works themselves. To fully understand your potential problems I would need to make a site visit and see for myself to give informed advice as to the best way forward. With regard to the exterior and the tyrolean I would really need , again, to see for myself. If the tyrolean has degraded , then due to the solid wall construction there is a possibility of penetrative damp. Should the tyrolean need to be removed then I would recommend applying a traditional two coat cement render system. Having sealed the brick work I apply a a first scratch coat, with a five parts plastering sand to one part cement ,to one part hrydrated lime mix with water proof additives, and simultaneously install a nylon meshing throughout, this mix and system delivers good adhesion and prevents cracking that can occur with even good rendering work. I then apply a second top coat for finish using the same mix and additive. With regards the use of specialist lime based mixes for breath ability, unless the property has complete lime based systems inside and out as it may have had when it was originally constructed then it doesn’t fully work. I would only use specialist lime based systems in pre Victorian property , or for listed or heritage work. Specialist lime product is three times the price and not necessary for your 1920’s property . Once dried the cement render can be decorated with a high quality masonry paint delivering a finish that will last many years . With regard Underhill decorators and property renovation