Damp and condensation problems Flashcards
What 3 categories are rising damp classified as?
rising damp
penetrating damp
condesnation
how can the 3 categories of damp be caused?
plumbing leaks
hydroscopic salts
what are key characteristic of water?
water can travel a long way inside a structure before it exits 1.5m
corners and folds are weak spots in a building
large stains can be caused by small amounts of water
building materials can act as a wick, drawing water to area where it can evaporate
rain can travel vertically up a wall when driven by wind
what is a simple framework for assessing damp?
map the area of concern in a basic sketch
look for obvious causes
look everywhere for what is not happening
collect all evidence and eliminate suspects
what steps are taken during an initial investigation of damp?
what further investigation can occur
use a moisture meter with care
carry out internal and external inspection
visual inspection of all internal ground floor walls
take photos and sketches
undertake calcium carbide tests
undertake a salt analysis
what indicators are there of rising damp?
usually rises 1-1.5m max sharp cut off visual evidence through tidemarks high moisture content of skirtings damp appears worse in humid conditions
what are causes of rising damp?
no DPC or failure of existing DPC
Resurfacing paths and drives or raised garden levels can bridge the DPC
splashing from rain of downpipes
render bridging DPC
build up of mortar in cavity can cause penetrating and rising damp
bridging by floor screed
the height that damp rises will be determined by?
porosity of the material evaporation heating (internal/external) porosity of wall materials chemicals in the water amount of moisture in the soil
what are the four ways a new DPC can be provided?
chemical DPC
physical DPC
electro osmotic DPC
evaporative DPC
what are chemical DPC’s?
holes are drilled into wall at various depths and chemical injected
cheaper and quicker than physical but difficult to check it is complete
beware of adverse chemical reactions
works best with brick walls and cement based mortars
what are pros and cons of physical DPC’s?
pros - installation can be seen to be completed
forms continuous barrier
stable and non reactive
easy to like to any DPM
cons - higher cost and longer installation time
internal plumbing and electrics may be in the way
difficult in thick walls and at uniform junctions
not suitable for non uniform walls
may cause stability problems
what is electro osmotic system?
based on theory that applied voltage affects capillary action
consists of titanium wire embedded in the wall through the wall which a tiny positive charge is thread
what is evaporative system?
based around a series of ports ceramic tubes embedded in the wall
what are main causes of penetrative damp in solid non cavity walls?
cracks usually the result of building movement
poor detailing
poor quality bricks, stone
leaks from downpipes, guttering, waste pipes, embedded pipes
poor detailing of parapet walls and of abutments generally
lack of chimney flashings and DPC’s
what are specific problems of cavity walls which can result in penetrating damp?
wall ties covered in mortar or upside down or sloping inwards
cavities full of debris
missing cavity trays or trays incorrectly positioned
missing DPC’s where cavit
