Post details: Impervious!


Permalink 08:49:40 am, Categories: Articles, 723 words   English (US)


The fundamental thing with regard to structures is to keep the elements at bay.

Rain and moisture; Though necessary for life, these are a nuisance, within the home.

Let's break them down a little.

Whether (weather, lol.) you live in Afghanistan or Armarillo, one reason to have a home is to live and sleep in relative dryness. Sounds obvious, yeah!

Well, here are some considerations. Depending where you live and its' associated environmental weather conditions, different building regulations and practices exist.

Cavity; The purpose of a cavity is to prevent water from going through the "inner leaf". This is a construction term and mainly applies to concrete or "block" structures. To a lesser degree, it is helpful in regard to thermal conductivity (example; double glazing of windows or window panes). An outer leaf of blocks extend upwards and outwards and a cavity or space is left between it and the inner leaf. With timber frame construction, this cavity may be dimensionally less. Timber frame construction adopts the attitude of "do not let it in, absolutely"), and this is achieved with plastic membranes of different compositions.

Where this is done properly, it is brilliant and efficient. Timber frame housing is becoming accepted or more normal, in and throughout Europe. Europe, traditionally was masonry orientated, but cost with respect to time, has brought about a change. Timber frame is faster to erect.

Bottom line. With concrete based structures, there is no definitive rain or moisture blocking membrane. Which do you think would absorb water, concrete or plastic?

Anyway, the theory is that once water gets through the outer layer of either construction type, it will meet a cavity, and go no further.

Exceptions. Bridging damp.

This is where dirty wall ties (masonry) exist. The build up of mortar, due to sloppy workmanship will allow moisture to traverse the cavity.

Similar deal with timber frame. How would you traverse a ravine without a bridge?

Capillary Action. This relates to the ability of moisture to "climb". Put almost any material into water, for example, and you will see the liquid climb, against normal gravitational perceptions. Rising damp works by this and atmospheric pressure in combination and must be considered in damp countries.

Human moisture. Some studies reveal that the average adult will expire a half litre of water, simply by breathing. A perfectly insulated home can be victim to this and ventilation is the answer.

Add to this, areas known as wet spots. Wet spots are areas that produce moisture from within the structure. Bathrooms and kitchens are probably the worst. You boil the kettle, boil your dinner, microwave your food, use the clothes dryer, etc., and the moisture must go somewhere. You see it leaving the kettle and shower as steam, and tend to forget about it. Well, it does dissipate, but it doesn't disappear, however perfect the illusion.

It will manifest itself against any cold surface or relatively colder surface. Single-paned glass is the obvious area of manifestation, but moisture can present itself upstairs, or at the other end of the structure. It doesn't necessarily go up the stairwell and can actually go through normal plasterboard that doesn't have a vapour barrier.

A common cause of "increased internally caused dampness" is drying clothes on radiators. This action seems like a good idea but remember that moisture doesn't dissappear, totally.

A gas heater is another offender. I'm talking about the mobile type as properly installed gas boilers are "vented" to the atmosphere.

Incidentally, moisture will affect the functionality of insulation materials, and lower its' "U" value. Again it can travel through plasterboard and other board, where a vapour barrier is absent.

The answer is wherever you see steam, vent it! That means install an extractor fan that will transfer it to the atmosphere (outside).

Get a clothes dryer (vented).
Reconsider that mobile gas heater.
Install a extractor fan in your bathroom. Ideally, this can be "wired" to come on with the shower. See a professional!

As "breathing" is necessary, continue this!
Ventilate your home! Trickle ventilation is one option where a fairly small vent is machined into your window frames and aren't very noticeable or ugly.

Larger vents in each room have regulation status in some countries and are important.

"Air and moisture are necessary, just remove the conflict".

Seamus Dolly



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