Sub Floor and Chimney Ventilation

Sub-Floor and Chimney Ventilation

Ventilation is key to keeping a property free of moisture and damp, which is good for the health of the building and those living within it. Because of its importance, a whole section of the building regulations is specifically concerned with this element of property construction and care.

The building regulations cover a wide range of ventilating methods. Here we consider two key, often forgotten, aspects of ventilation that should be observed to keep your property free of damp:

On a Side Note: - Here the best selling DIY product for home owners in 2012... over 4500 sold in NZ already! - Watch Demo Video Here

Sub-floor ventilation

Many traditional properties are built with a suspended wooden floor which sits above a void air space between the perimeter walls and ground. If this space is not ventilated, the air in it becomes stagnant and humid, and the moisture within it begins to condense on the brickwork and flooring. Over a prolonged period, this moisture causes the floor to rot from the underside.

To avoid this situation airbricks must be positioned in the wall such that air can exchange freely between the sub-floor void and the outside. These airbricks are manufactured in terracotta and plastic to approximately the size of a standard brick, and one should be inserted in the wall every 180cm (5ft 11in), on all sides of the property.

Once you have sufficient airbricks in place, ensure that they can work properly by keeping them free of debris and dust. Particularly if you have cavity walls to which insulation has been added, ensure that the passage of air has not been blocked.

To insert an airbrick in a solid wall, simply chisel the mortar away from one brick in the wall and replace it with an airbrick and repoint.

In a cavity wall, the airbrick should be inserted into the exterior leaf of the wall as for a solid wall, but you will need extra long drill bits (300mm, 12in) to cut through the interior leaf of the wall as well and thereby maintain the through flow of air to the sub-floor void.

To prevent debris blocking the cavity between the two holes, fit a telescopic ducting sleeve to the back of the airbrick and extend it through the hole in the internal wall.

Where the exterior ground level is too high to carry air to the sub-floor void in a straight line, a telescopic underfloor vent should be attached to the back of the air brick to conduct and protect the airflow across up to 5 brick courses.

You will need to chisel out a much larger area than a single brick to be able to pass the angled duct through.

What Causes Damp?

Chimney Breast Insulation

Despite ‘period features’ being a highly attractive attribute, it is not uncommon these days for fireplaces to be covered over.

Under normal circumstances, a fireplace allows air to flow freely through the chimney upwards and downwards depending on the prevalent weather conditions. If the fireplace has been panelled over, it is absolutely imperative that the air inside the chimney breast can continue to move so that it does not become stagnant and cause condensation and then damp.

If the fireplace has been bricked up, check that at least one airbrick has been included, and if not, insert one in a low, central position. The plaster immediately on top of this brick must also be perforated to avoid interrupting the air flow.

If the fireplace has been covered over with a wooden panel, this must also include one or more holes. The simplest approach is to drill several holes of 12mm (½in) diameter into a low central portion of the panel. Alternatively, for a more professional look, a large hole can be cut into the panel in the same position, using a keyhole saw, and covered with a vent grill. Ensure the hole is 10mm (⅜in) small on all sides than the vent itself so the vent can be screwed on.

Moisture can destroy structural integrity of your home. Call us today, we can detect moisture issues in your home that the human eye can not see which may need immediate attention.

Similar Posts:

Get a free 'over the phone' quick quote HERE

Best Value - Our home infrared 'Quick Scan' Details Here!

Do the moisture inspection results go on my LIM report? - Details Here

Thermal Imaging

Client Comments... (All testimonials can be verified as true and correct... updated in 2011)

I enlisted Dean’s services 2 days prior to “D-day” of us purchasing our first NZ home. Dean proved to be an extremely efficient and knowledgeable technician. He has a very good understanding not only of his specific field, but also of general building requirements. He was easily able to spot, and talk me through, existing as well as potential problems, and was very open to answering the myriads of questions I fired his way. Most importantly, he gave me non-biased answers, allowing me to make an objective decision regarding the purchase of a potentially leaky home. Thanks again for excellent service Dean! Simone P - Titirangi

We have lived for some time in an old weather board cottage which we have renovated over a period of years. Recently we discovered a leak, so we googled “find a leak” and found a comprehensive and detailed website of the same name. Next we spoke to Dean and an appointment was made. He was punctual, courteous and his experience was obvious. His thermal imaging equipment is ‘state of the art’ and the source leak was quickly detected.

Dean was able offer practical solutions which we can act on with confidence. As a result of this experience we would recommend the use of his skills before the sale or purchase of any property to be reassured as to the integrity of the property. Dean is personable, a superb communicator and a true professional. Maggie & David M - Waiatarua

Dean was very professional and I would highly recommend anyone that is thinking of buying a property to get thermal testing done. Fortunately it was by pure chance that I even knew these tests were available after speaking to my neighbour and he advising me. The house we were looking at had water leaks and Dean has saved me many thousands of dollars in the long run. David G - West Auckland

Dean is a very professional and friendly guy. He goes step by step through the process which is very valuable. When he finds a potential problem he immediately notified to me and discussed with me in details on what actions could be taken. Anyway no major problems were detected in the property I wanted to purchase. However I greatly advice anyone to obtain Dean's professional service to make sure the property is in a satisfactory condition. Robbie P - Glen Eden

Thank you very much for the great service, very professional and appreciated the time taken to explain the process. Very glad to know that with all the stigma that goes with plaster houses, ours is not a leaky home. The report has helped pin-point some areas for maintenance which we plan to undertake sooner rather than later..Thanks again. Heather M - Maraetai

We were a bit apprehensive about what the leak detection might find, but found Dean’s confident, friendly and very capable approach extremely reassuring. While we were greatly relieved by the findings concerning the exterior of the house, Dean’s thoroughness in looking also for internal issues uncovered a surprise bath leak. Thanks Dean for solving the mysterious odour that’s been bothering us for the last 6 months! We highly recommend Dean to anyone with even the slightest concerns regarding moisture in their homes. Kevin - West Auckland

Thank you Dean for your prompt service. I was given 2 days to have a Building inspection done which found some dampness in the house. It was well worth the money spent as Dean found some other damp issues. He was very thorough and very informative and even though there were issues with the house they were all fixable so I was then able to re negotiate the purchase price. I would recommend anyone buying a house- any type of building structure to have ’Thermo Imaging’ as part of a building inspection. Thank you once again. Maree, Glendowie

We had some concerns about a recently renovation house including a lower basement. Being nosey I popped around to join Dean on his inspection. Apart from enjoying meeting him, Dean was enormously informative, approachable & friendly, I found the technology & information I gleaned fascinating. Fortunately, we identified no significant issues with the property. It gave us great peace of mind & we can enjoy our new home knowing we have bought a dry, water tight property with with hidden surprises. Thank you Dean for your help & reassurance. To my mind it is certainly worth the modest sum versus potential costs you could incur which could also mar one of most expensive purchases of your life.. Diane - Devonport

Read 20 more testimonials Here!