How does water get into cavity walls: What to do when water comes pouring into your house?

What to do when water comes pouring into your house?

Laurence Wright

Laurence Wright

Property Investor – Architect, specialising in residential property

Published Feb 20, 2020

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Verity Lovelock @bbd-architects recently shared her horror story of water cascading through her ceiling after the recent storms. Imagine waking up to a waterfall in your dining room, raining just as much inside as outside?!

And how could this occur in an architect’s house? Did they not detail it correctly? Well, in this case, she inherited the problem without knowing; a missing cavity tray. And why has it only just happened, why has it never happened before? Rain and water can behave strangely around buildings. Most rainy days it does not cause a problem then get the wind direction just right and bingo; floods of water.

Here’s the technical bit:

Cavity Trays are used in cavity wall construction to prevent water ingress below an abutment. They can be installed either horizontally or at an angle where a pitched roof meets a wall. At a pitched roof abutment they are called Stepped Cavity Trays.

Surprising as it sounds, rain will travel through the external brickwork skin and into the cavity quite easily and that’s why there is a cavity. Heavy rain and a strong wind will push the water across the cavity too. Any water in the cavity has the ability to get inside the building unless it is redirected back out of the building via a Cavity Tray. Without the Cavity Tray water in the cavity will travel with the help of gravity and may then find itself passing through a plastered ceiling, most likely through an existing hole or light fitting, just like it did for Verity.

Normally cavity trays are installed during construction. However, in some instances they can be found to be missing or damaged. They can be retrospectively installed, though this is a slow process. Simply put, a bricklayer will remove two or three bricks at a time to install a section of Cavity Tray at a time. This allows the untouched element of wall to remain supported while replaced brickwork and mortar sets. Taking the entire length of Cavity Tray brickwork out at once will risk brickwork above the opening collapsing or being damaged. It’s important that the new tray is tucked into a mortar joint of the inner skin of the cavity wall to ensure all potential cavity water is diverted.

What risk or damage could I expect?

A missing Cavity Tray can cause no end of damage to built fabric and the interior of your home and furnishings if water finds its way through. Immediate and significant issues could be fire risk with water passing through light fittings, which is obviously quite a concern. Water has a habit of finding a route to flow through and will pool on plasterboard until it finds a hole, perhaps around a light fitting. Moderate risk will be damage to the built fabric. Moisture in timber, for example, will cause it to rot over time, which ultimately could cause collapse or toxic mould and breathing problems. In the least, after water exposure, you are likely to see brown staining on plastered finishes that will need, after drying, to be sealed and redecorated.

So how do I know whether I have cavity trays or not?

Apart from an indoor waterfall, it is very difficult to determine whether you have one without investigation. Weep holes are a reasonable suggestion (but no guarantee) that there is a Cavity Tray. It’s also possible to have a Cavity Tray without weep holes, though not ideal. Weep holes allow water within the cavity to escape and are installed where a Cavity Tray meets the external skin. The easiest investigation is either spotting a waterfall inside your home or removing a couple of bricks and taking a look.  

If you are in doubt, or like Verity have an unwanted indoor waterfall feature, invite a suitably qualified builder to investigate the presence of a Cavity Tray for you. When having a Cavity Tray installed, ensure that it is tucked into the inner skin mortar joints (without impacting any insulation) and that weep holes are installed in the outer skin where the Cavity Tray meets the external skin.

Wet Cavity Wall Insulation – Wall Cavity Claims

In the past majority of cases, Cavity Wall Insulation worked well, or so it seemed. It should keep your property warm and function well for the life of its guarantee (typically 25 years) and well beyond. Houses that are suitable for cavity wall insulation, with standard brick or block clear cavities between 50 – 100mm that are not unduly exposed should experience no problems. However, when cavity wall insulation has been installed improperly, or to unsuitable houses, it is more than likely to fail. The most serious of all issues we encounter with failed cavity walls is wet cavity wall insulation.

Wet cavity wall insulation can occur for a number of reasons. The first and most common is exposure to wind driven rain, often accompanied by eroded mortar joints. Bricks are porous and, if walls are prone to very harsh weather conditions, rainwater can enter the cavity to such an extent that, over time, the cavity wall insulation becomes soggy and slumps. If cavity wall insulation is installed to the correct density then water should not transfer across it in all but the most exposed of locations. However, if the density is wrong, or there are void areas, water ingress can be a problem. Another common reason for wet cavity wall insulation is water ingress through points of weakness in the fabric of the building. This can include, but is not limited to, seals around windows, guttering, downpipes and in the eaves, fascia or soffit areas of the roof. It is vitally important that property maintenance is attended to regularly to retain a sealed dry cavity wall. A third reason for wet cavity wall insulation is as a result of flooding. Naturally, flood waters breach the cavity wall and will saturate it inside and out. Cavity wall insulation therefore becomes very wet and slumps.

Unfortunately, in our experience, it is very difficult to dry out wet cavity wall insulation. Even if it does dry out, it becomes lumpy and loses a large part of its insulating qualities. Of course, while it is wet, it can have a very damaging affect on the property, allowing water to move through the inner leaf and cause internal damps problems in the plaster and decoration. At the same time, wet cavity wall insulation is having a cooling affect on your property, not unlike wearing a wet jumper would on your body if you went outside on a cold windy day.

For this reason, our advice is always to remove the wet cavity wall insulation and allow the cavity to fully dry out before considering re-installation.

If you’ve got issues of any other nature with your Cavity Wall Insulation that may be down to the installer not following proper guidelines as to the install. It is now apparent that hundreds of thousands of home owners across the UK will need remedial work that will consist of a full extraction of the Cavity Wall Insulation and could well mean a whole host of other repairs and replacements directly caused by the install.

Contact Wall Cavity Claims today on free phone 0800-8-654321 or visit

§1. Water in wood|Engineering and manufacturing of equipment for sawmilling and wood drying company OI. Innovation

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  5. §1. Water in wood

Water in a tree trunk

Sapwood and heartwood

Tree trunks that we use as lumber are filled with water because they conduct water from the roots to the leaves.

It is surprising, however, that not the entire trunk, but only its outer part, conducts water. This part is called sapwood (or outer layer). In most trees, the sapwood is rich in moisture, and the inner core (red zone in the figure) contains less moisture (see Table 1)

in the sapwood. The humidity of the core part with this method of drying almost does not change.

High core moisture

Japanese cypress (hinoki) 153.3 33.5 Sequoia 186.0 56.2 Pine 147.3 33.7 Cryptomeria (sugi) 148.0 113.1 Spruce 169.1 40.6 Fir 211.9 76.1 Cypress 154.5 38.3

There are exceptions in the world of trees – some types of wood contain a large amount of moisture in the core, although it does not participate in the conduction of water.

As can be seen from Table 1, an example of such a breed is the Japanese Cryptomeria. Adding to the complexity is the fact that the moisture content of cryptomeria heartwood varies considerably from log to log. This makes it difficult to dry cryptomeria lumber.

1 As a rule, in freshly cut wood, the side or sapwood is more moist, and the heartwood or core has a low moisture content.
2 There are some woods, such as Japanese cryptomeria, which have a large amount of moisture in their core.

Water in wood

Cell wall and lumen

Micrograph of a tree (spruce) ). As you can see in the photo, the cells are hollow inside. In fact, most of the cells in the tree are already dead and have no content. The empty space is called the cell cavity, and the partitions between the cavities are called the cell wall.

Free and bound water

Cross section of a cell (perpendicular to the direction of tree growth)
In freshly cut wood, free water is present in the cell cavity, and bound water is present in the cell wall.

Water passing through the stem passes through the cavities of the cells. This water is called free water because it is the same as ordinary liquid water. In addition, some water enters a small space in the cell wall and is called bound water because it forms the molecules that hold the tree together. In other words, wood contains two different types of water: free and bound water.

3 There are two kinds of water in wood: free water and bound water.
4 Free water is in the cell lumen, and bound water is in the cell wall.

Humidity control valve: cell wall pores

Role of cell wall pores

As water moves between cells, it passes through many small pores in the cell wall, called wall pores. This hole in the wall is not just a hole, but a valve called a membrane that controls the flow of water (see picture).

Microscopic examination shows that the membrane consists of a mesh filter (Margo) and an inflated cap (Torrus) (see photo).

Closed cell pores of heartwood

Electron micrograph of cell wall with pores

Valves or pores in sapwood cells open and close quite freely. Heartwood does not allow water to pass through, so after the passage of water, the pores close and stick tightly (dry core effect). But there are breeds, such as cryptomeria, in which water got into and stayed in the cells of the nucleus. The peculiarity of such tree species is that the water in the heartwood is tightly sealed inside the cells. Therefore, the movement of such water is difficult, and the drying of heartwood takes longer and requires more energy than sapwood.

5 In sapwood, the pores of the cell wall act as valves that regulate the movement of water.
6 In heartwood, water is in the cells in a clogged state.

Methods for expressing the moisture content of wood

Water content on a dry basis

The moisture content of wood can exceed 100%. If this happens, you may be concerned about water overflow. The moisture content of wood must be calculated using a method called the dry weight standard, and it is not just a wet weight standard indicating moisture content. This marking indicates the weight of moisture content relative to the weight of completely dry wood (total dry weight), so the moisture content can be higher than 100%.


Wood containing the same weight of water as total dry weight = 100% moisture

Wood containing twice the dry weight of water = 200% moisture

Wood containing half the total dry weight of water = 50 moisture %

Dry wood moisture content

The water content can be measured by the total drying method, electrical resistance type moisture meter or high frequency type moisture content meter. The general drying method is a method that accurately measures the moisture content. However, there are problems in that the moisture content of a large material is represented by a small test piece and the material must be destroyed. Therefore, this method is suitable for use in sampling and control for quality control at production sites.

7 Wood water content = wood water weight/total dry weight × 100 = (Wood weight in a certain moisture state-total dry weight)/total dry weight × 100

Moisture and water condition in wood

Fiber saturation point

In all wood, the water content is generally 30%, and the presence of water varies greatly. This water content is called fiber saturation point, where the cell wall is filled with bound water. When the water content exceeds 30%, water (free water) is also present in the cell lumen.

Conversely, if the water content drops to 30% or less, the water content of the cell wall decreases. As bound water decreases, the cell wall itself gradually becomes thinner.

As a result, wood, which is a collection of cell walls, gradually shrinks. In other words, shrinkage due to wood drying is a phenomenon that occurs below the saturation point of the fiber (30% moisture content). Below the fiber’s saturation point, various properties such as strength change greatly with changes in moisture content.

Schematic diagram of moisture content in wood

Equilibrium moisture content

If wood is placed in an environment with elevated temperature and humidity, it will eventually have a moisture content balanced with that environment. This moisture content is called the equilibrium moisture content. Depending on the season and region, Japan’s average equilibrium water content is believed to be around 15%. In addition, the equilibrium water content of an air-conditioned room is likely to be around 10-12%.

8 Approximate moisture content of 30% is called fiber saturation point.
9 Above the saturation point of the fiber, both free water and bound water are present.
10 Below the saturation point of the fiber, only bound water is present and the wood shrinks.
11 The water content balanced with the environment is called the equilibrium water content.

Nasal liquorrhea – what is it?

Nasal liquorrhea (NL) – the outflow of cerebrospinal fluid into the nasal cavity – is a rather rare, but potentially fatal disease that is far from always correctly diagnosed by doctors and can exist for many years under the guise of allergic or vasomotor rhinitis. CSF fistula (a channel through which fluid flows) occurs due to a defect in bone structures and meninges. If the bone defect is large, the membranes and substance of the brain can fall through it, creating a hernial sac called a meningo (encephalo) cele.


Such a fistula can form as a result of a craniofacial trauma preceding surgery in the nasal cavity and at the base of the skull. Or spontaneously, against the background of increased intracranial pressure. Thus, traumatic and spontaneous nasal liquorrhea are distinguished. In turn, spontaneous nasal liquorrhea can be congenital, as a result of intrauterine disorders in the formation of bone structures of the skull base, or acquired. In the latter case, a fistula can form against a background of various problems. These include metabolic disorders, increased weight, increased intracranial pressure, anomalies in the development of the anterior sections of the skull base, etc.

What is the danger?

In itself, the abundant discharge of fluid from the nose is quite unpleasant, since it seriously reduces the quality of life. But a more serious complication is meningitis, i.e. inflammation of the membranes and the substance of the brain, since there are conditions for the penetration of infection from the nasal cavity into the cranial cavity in case of any catarrhal disease. Another formidable complication is pneumocephalus, when air is introduced into the cranial cavity through an open fistula. These complications require emergency hospitalization of the patient.


Symptoms of profuse nasal liquorrhea:

When the head is tilted, a clear, light liquid is released from one half of the nose.

Hidden, recurrent nasal liquorrhea is more difficult to diagnose and requires the use of the entire arsenal of techniques – laboratory and radiation. In the supine position, a cough occurs, since the liquor flowing into the oropharynx can enter the lower respiratory tract, causing reactive laryngitis, tracheitis, and even pneumonia. Liquorrhea complicated by meningitis is manifested by a wide range of neurological disorders.

A patient with nasal liquorrhea usually has a history of traumatic brain injury or surgery involving the nose and paranasal sinuses, including endoscopic surgery. In this case, spontaneous nasal liquorrhea can begin suddenly without an obvious apparent reason.


First of all, the doctor determines the nature of the discharge:

  • the side from which the discharge comes,

  • periodicity,

  • the specific positions of the head at which they appear,

  • dependence of the volume of secretions on voltage (Valsalva test).

The figure shows a visual examination of the patient. When the head is tilted down, a clear liquid begins to stand out from the nose.

Nasal liquorrhea is often mistaken for rhinitis (allergic or vasomotor). She can also remind patients of the state when the nose is irrigated with liquid medicines.

Profuse nasal liquorrhea may stop on its own for some time, while patients report headache due to fluctuations in intracranial pressure.

Damage to the anterior parts of the base of the skull may be indicated by:

The standard examination must include:

  • Endoscopic examination of the nose and paranasal sinuses (in the figure – endoscopy of the nasal cavity with a straight endoscope; in the projection of the posterior wall of the sphenoid sinus, a small bone defect is visible through which CSF enters).

  • Rhinoscopy.

  • Hearing examination for the presence of ear liquorrhea,

  • neurological examination,

  • Biochemical analysis of liquid nasal secretions for glucose levels, determination of proteins specific for cerebrospinal fluid (beta-2 transferrin fraction, trace protein).

Imaging methods:

  • Computed tomography (CT) of the base of the skull and paranasal sinuses (the figure shows a large defect in the base of the skull in the projection of the sieve plate with the formation of a meningocele (shown by an arrow)).

  • CT cisternography with endolumbar contrast injection to more accurately determine the location of the defect at the base of the skull. This study is performed in a hospital setting.

  • CT scan of the skull and brain to rule out hydrocephalus, neoplasms of the base of the skull, and to identify meningocele.

  • Magnetic resonance imaging (MRI) is an adjunct to CT to rule out meningoencephalocele.

  • CSF-sensitive MRI. It is non-invasive, has no radiation exposure and takes slightly longer than conventional MRI.


Treatment of nasal liquorrhea is mainly surgical. For many years, it required severe, sometimes disabling interventions on the base of the skull using transcranial approaches. Over the past three decades, the development of endonasal endoscopic surgery methods has radically changed the situation, and now most cases of nasal liquorrhea can be cured by sparing minimally invasive interventions performed without external incisions through the nasal cavity under endoscopic control, which allows the surgeon to significantly improve the overview of the surgical field. The endoscope helps the surgeon determine the location of the CSF fistula, carefully separate the mucous membrane from the bone defect, and accurately place the graft at the site of injury.

The method of surgical intervention is determined jointly by an otorhinolaryngologist-surgeon and a neurosurgeon. In some cases, neurosurgical intervention is required. For example:

  • Large or multiple bone defects.

  • Traumatic brain injury with compression of the brain.

  • With increased intracranial pressure, when a fistula repair cannot be performed before the hypertension has been eliminated with bypass surgery.

  • With a complex location of the fistula.

Treatment of nasal liquorrhea is primarily aimed at restoring the barrier between the nasal cavity and the intracranial space so that intracranial infection does not develop. At the same time, soft tissues, rather than bone fragments, can be used to repair small defects in the base of the skull. But with large bone defects, they must be closed with a dense cartilage graft so that an encephalocele (cerebral hernia) does not form.

Postoperative period

After surgery, patients are usually advised to follow the following recommendations: avoid increased physical exertion, prolonged straining, forced coughing. The mode should be as gentle as possible. If possible, try to be more in a lying position, raise the head end of the bed. If signs of nasal liquorrhea completely disappear, the patient is discharged with recommendations that must be followed for at least 6 weeks.

Within 3-10 days after the operation, it is recommended to carefully remove some of the tampon fragments from the nasal cavity. At the same time, absorbable materials located directly near the graft remain and are removed later. For the entire postoperative period, antibiotics are prescribed in doses that prevent the development of sinusitis.

In the late postoperative period, at each visit of the patient, an endoscopic examination is performed to exclude the recurrence of the encephalocele, especially if a large defect has been repaired. It is important in the future to carry out a differential diagnosis of rhinoliquorrhea with allergic, vasomotor and viral rhinitis.

Summary : thus, CSF rhinorrhea is a rare but rather dangerous disease that can lead to serious complications, including meningitis and pneumocephalus.