My mate over the road had a leak in the bathroom causing water to pour through the ceiling & soak the hall carpet.
He reported it to his insurance co, who sent Chem Dri around to do a report.
They used a 'moisture meter' and determined that the ceiling had a 20% moisture content and the flooring 100%. Apparently the 'criteria' is that below 17% moisture in a floor or ceiling needs no action, anything above does.
My mate doesn't care because the insurance co are paying, but do I detect the smell of bullshite here?
I thought moisture meters were only useable on wood, not floors & ceilings? Where does the 17% 'criteria' come from? And isn't 100% moisture content - just water?
If the ceiling is plasterboard and it is not actually 'falling' apart (some minor bulging is allowed) - then if it's left alone to dry naturally it will be ok.
Depends on the severity of the damage - and if the ceiling has retained its position after a 'soaking' and a moisture meter has to be used to detect the damp, then the answer is *no*.
One can also be used on walls (to detect rising damp etc) - and as for 'moisture content' your own body is around 90% moisture (IIRC so don't hang me on that one) and the moisture content of the timber that you use in your decking is around 18% - 22% - oh! and a 100% moisture content of the plasterboard will guarantee a new ceiling. :-)
A tip BTW, to reduce water damage to a plasterboard ceiling after a leak, find the lowest point where the water is coming from and simply bang a screwdriver through the ceiling and let the water drain into a bucket below - and then leave well alone until the ceiling is dry - This will usually 'save' around 60% to 80% of them.
Seen hundreds of 'em Dave over the years - even in my own house when the CH sprang a leak.
The reading is only valid on wood. The meter (or any multi meter) is useful to indicate presence of moisture in masonary, but the only way to actually measure it is to take a lump of the masonary, weigh it, dry it out, and weigh it again to see how much mosture was present.
I'm told that the salts that may be present in many materials can strongly influence conductivity, particularly where it's caused my migrating damp, as salts can be transported and concentrated.
I'd imagine to get an accurate reading you would need a set of samples of that material at known moisture levels to calibrate from, as I wouldn't expect conductivity to be particularly linear with moisture content, or consistent between different materials.
Indeed. An unusual ceiling construction there. Seriosly those meters are well known for their inaccuracy when used on things other than wood.
This is a handy ref by buildingpreservation.com, highlighting the difference between carbide (invasive) and electric (non-invasive) moisture meters
formatting link
know the RICS caution surveyors about relying overmuch on meters and prefer experience, touch, smell etc to determine damp. However the may be some further notes in the links in RICS Books:
17% is the level at which softwood supposedly ceases to be vulnerable to a whole load of fungal infections. Scandinavian redwood is termed "shipping dry" at 17%, mainly to avoid the dreaded blue stain.
Well, it's that too, and the level at which it can be machined without tearing the grain. All good reasons why timber exporters need to get it down to that level prior to shipping, especially as it often spends months strapped up in 5 cubic metre packs without any circulation of air between the pieces.
Some interesting points in that article, but at the end of the day its just another example of very biased writing reaching a conclusion not logically supported.
To explain further:
Frst the article completely ignores a number of real world issues, such as changes in conductitivety caused by: past spills contamination deposits from past leaks kitchen cooking contamination detergent contamination inappropriately applied foil backed paper lime mortar behind cement mortar
These things are common in century old properties, which is the type of property these damp detectors are most used on.
Then there are several issues the article mentions, but then chooses to overlook: Lime mortar giving high readings Lime plaster ditto Presence of salts from sources other than a present damp problem Damp at non-problem levels "Unfortunately, the majority of surveyors do not appear to understand how an electrical moisture meter should be used" "using it like this will almost certainly lead to a high number of wrong diagnoses!" transient surface condensation condensation Surface readings being a problem in winter Surface readings being a problem in summer "The isolated individual readings obtained during most surveys are of little value and will certainly increase the chances of misdiagnosis!"
There are some good points made in the article, but as a piece of logical writing it simply isn't.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.