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Cavity wall insulation problems. From Wall ties to damp ingress

When you have your cavity wall ties replaced, it can often leave nasty scars, so what do you do?

Wall ties hold the 2 parts of the cavity wall of your house together, but what happens when they get replaced and how do you deal with the mess it leaves behind?

If you have had cavity wall insulation, did you start getting damp walls?

We look at these thorny problems and offer a solution.

How do wall ties fail?

Over time a porous wall, especially one that has driven against it by the wind, allows water into the cavity and then rusts the small metal ties which are there to hold the 2 parts of the wall together.

If they rust away and then fail, this can cause a serious lapse of structural integrity to the property itself.

What happens when wall ties need to be replaced.

Having a wall covered in bare render on old, unpainted brick, can mean the weather repelling properties of the wall covering are not as good as when the home was built.

It is rare to have to have wall ties replaced, unless the building is of a particularly poor quality build in the first place, or you have years of rain soaking into the wall and rusting the ties.

These types of surfaces can absorb a lot of water and damp when it rains, especially combined with a driving wind too, which literally forces the water into the walls, to cause you more issues, such as rusting your wall ties.

You can see a section of wall below which shows the metal rods which hold the brick wall (external) and the block wall (internal) together so they do not collapse in on one another. Older homes with solid walls do not have this system.

wall ties and insulation inside a cavity

The cavity acts as an air barrier supposedly making a house with thin walls, warmer inside. Most modern homes have walls like this.

What are wall ties I hear you ask?

They are small metal (usually) strips with a dip or twist in the centre, and are built into the house by the bricklayer, and bind the 2 “leaves” of a cavity wall together.

The above image shows the 2 leaves or wall sections of a house, but in this case, insulation has been added inside the cavity to give the occupants a much warmer house.

When a house is buffeted by driving rain and the water soaks into the wall, the twist in the middle of the wall tie allows the water to drip off, inside the cavity, and onto a cavity tray, which dissipates the water away from entering the inner leaf, essentially, your interior walls.

When this happens, you start to get damp in the house, which can cause all manner of problems.

So what can be done to avoid all this?

When wall ties are replaced it is often best to contact an accredited wall-tie replacement company who have the right experience and knowledge to carry out the work.

If you choose to ignore rusty wall ties, eventually the walls can start to “bow” (Bulge outwards) and then in the worst scenario, the outer part of the wall can collapse.

This is because the steel wall ties hold the 2 sections of wall together and when they rust, as is often the case with older iron ties or steel (but not stainless), the house essentially loses its tensile strength, or the ability to hold the 2 sections of wall together.

Worst case scenario is the outer leaf of the wall simply collapses outwards due to the fact it is not being held together anymore.

When a wall tie replacement company carry out the work, they remove and replace all the old wall ties, giving your home back it’s strength.

This is because cold weather attacks the fabric of each house, and water gets into any small cracks that may be present on the render or pebbledash, and then expands when it freezes, making the cracks EVEN WORSE and even harder to fix.

It is this freeze and thaw action during the winter months that can cause more damage to your house than you ever thought possible.

If you have not had your home protected with one of the NPA Weather protecting wall coverings, then you can be sure it has happened for the past few years to your house.

However, as far as appearance, the wall can look ruined, like this one below.

AFTER WALL TIE REPLACEMENT
This is the mess we had to sort out when a client had cavity wall ties replaced

As you can see, there is a network of scars on the wall now, where the wall ties were replaced.

No matter how good a decorator is, you cannot apply normal masonry paint to the walls of a house like this and not expect to see the same scars grinning out through the paint.

It really doesn’t look very nice, does it?

The ONLY way to cover this effective is with the use of a textured masonry coating, which being 20 times the thickness in microns, of a normal film of paint, will cover and hide the scars, giving a pleasant and uniform wall finish.

 After wall tie replacement…

After they have been replaced, our teams apply our special exterior wall coatings to the house, which last up to 20 years and do not fade, crack, chip or peel and it is the best house wall painting system around.

The NPA wall coating painting system also benefits from a 20 year warranty, available direct from the contractor.

All this sounds expensive yes?

NO…!

Well as we do a “holistic” exterior repair and decoration to your home, the cost comes right down as you do not have to employ several different tradespeople, just to get the place repaired and painted.

Start saving money and give us a call now.

We can be reached by dialling (0800) 970 4928

You can also send the team an email here.

Cavity wall insulation, is it good or bad for my house?

Cavity wall insulation is defined as the injection of an insulating material (usually recycled cardboard, rockwool or polystyrene balls) which fill the cavity (the space between the inner and outer walls) of a house and provide a thermal barrier.

There are tremendous benefits to this system, although there are critics of it too and we look at both sides of the argument here and we suggest viable alternatives to having cavity wall insulation.

In general cavity wall insulation is fitted for a reason; i.e. to cure the symptoms of cold walls and wind chill.

This also has a positive effect on lowering heating bills, however there are some drawbacks too, AND there are alternative ways to insulate your home.

Cavity Wall Insulation, is it a good idea?

Cavity wall insulation is a method if creating a thermal barrier in a house, however it can cause more harm than good and can transmit damp into the house by forming a bridge between the inner and outer leaf of the wall.

The three main types of Cavity wall insulation.

Rockwool

1. A popular and widely used insulation product is made from mineral wool insulation, and is known as Rockwool and is made from stone wool – a blend of naturally occurring volcanic diabase rock.

2. Polystyrene balls. These tiny balls are injected into holes in the wall with a special pump, usually mounted within the teams lorry. (NOTE, NEVER PAINT AGAIN does NOT offer this system)

3. Insulating foam. This is the less commonly used option and is often made from either polyurethane or formaldehyde foam, which must comply with BS:5618  and BS5617

Good or bad?

On the face of it, insulating a cavity wall seems a good idea, however not everyone agrees….

Houses with cavity walls were built to keep out rain driven by the wind, however if the cavity, the gap between each “leaf” of the walls, is filled, there is, some would say, a risk that moisture will then have a way of bridging the cavity and entering the house.

This can cause DAMP where previously it did not exist.

Another problem can be the “wall ties”, the metal rods inside the cavity which help to hold each side the wall together; they can rust when cavity wall insulation is injected, and in the worst case, can cause the outer leaf to fail and come tumbling down into the street or worse.

Of course the cavity wall industry denies this.

And from our viewpoint, it also leaves scar marks across the wall where the team have installed the insulation, meaning that you now have to have the exterior of the house painted with a thick durable paint to hide the blemishes!

 

How is suitability for cavity wall installation ascertained?

An authorised contractor will survey the house to determine whether cavity wall insulation is suitable and would commonly look at the following factors.

The exposure of the walls of the house to driving rain, the condition of the masonry joints or “pointing” of the masonry outer leaf, the type of insulation material required and finally, the masonry material itself is considered.

Alternatives to cavity wall insulation.

If filling the cavity walls of your home is not something you feel you would benefit from, then there are other alternatives available, from NEVER PAINT AGAIN.

Exterior spray applied wall coatings

These value for money external wall coatings help in reducing wind chill and curing damp.

All of which can make a house very cold if not treated.

Not only does this high performance external wall covering system cure wind chill and cold walls, it also stops damp, and does NOT need repainting for up to 20 years!

Exterior thermal render

This system is an addition to our already popular coloured render and has thermal insulating mesh built into the walls before application of the final aesthetic coat of render.

This amazing system has excellent thermal properties and is suitable for most houses.

Solid wall insulation

Solid wall insulation obviously does not apply for cavity walls and therefore is not suitable, but if your home was built before 1920, chances are it will not have a cavity so that form of thermal insulation isn’t any good.

Exterior retro fitted insulation from NEVER PAINT AGAIN is by the far the best way to insulate a house without cavity walls.

External wall insulation is a layer of material, sometimes boards or sometimes insulated render, applied to the external walls of the house.

applying thermal insulated blocks
2. Applying and fixing the insulation

This can also take the form of cladding, or brick slips, insulated boards which, when fitted to the house, makes it look like the property has a brand new brick wall.

So what’s the answer to insulate my house?

So as you can see cavity wall insulation has its pro’s and cons but overall, if done correctly, big savings can be had on heating, and in some areas of the UK insulation GRANTS and other financial help is also available.

(UPDATE: Many local authorities have now discontinued such grants. July 2022)

It is worth remembering that GRANTS paid to homeowners for cavity wall insulation are paid for BY TAKING HIGHER TAXES off everyone!!

However, cavity wall insulation can actually cause more problems than it can cure, but if you choose one of our exterior wall coatings, insulation or render systems, you will have the same benefits and MUCH more!

This also includes the fact that we guarantee your house will look amazing, usually in only a few days, and you will get all the thermal benefits of installed cavity walls insulation and much more besides.

We are exterior wall coating contractors and, as such, we offer to remedy walls that have been damaged by cavity wall insulation and our sales line is for SALES ENQUIRIES ONLY please.

Thank you

Written by surveyor Guy Alexander Bell. Bsc.(hons.).Pg.Dp.

Why having cavity wall insulation can actually cause damp and mould in your home and what to do about it

 

We often hear about the benefits of having cavity wall insulation and the much lauded saving on costly fuel bills, but did you know that in some properties it can do more harm than good?

Let’s first make it crystal clear though, this is not applicable to all homes with cavity wall insulation, in fact in some cases, having walls filled with those little white beads can drastically warm up a cold home and significantly reduce heating bills, which is good in anyone’s book.

There are some things you really need to be aware of if you are thinking about having it done, or have had insulation fitted and are now suffering from mould on the walls indoors when you thought those days were over.

First things first, to break a common piece of bad advice you will no doubt find online, OPENING A WINDOW WILL NOT CURE THE DAMP IN YOUR HOUSE!!!!!

It’s a bit of a paradox really, surely insulation in your walls is a good thing?

Even the government get in on the act and offered generous grants to all kinds of homeowners to get walls insulated and stop the waste of carbon and greenhouse gas, so what’s the deal here then?

The energy saving trust suggest that with this type of home improvement on your home the average savings for a detached house would be at least £250 a year and a semi, the savings would be £150 a year

(source: energysavingtrust.org.uk/Insulation/Cavity-wall-insulation) however when you think about it, it’s not a HUGE saving but it does look good on paper though eh?

How can something that, in theory, sounds great, actually be a bad thing? Let’s explain a couple of things first.

What is cavity wall insulation?

For those who don’t know, most houses built after 1930 have 2 walls in their construction, the inner walls that surround you indoors, and the outer walls with render, paint or pebbledash on them, for example.

There is a gap of only a few inches between the 2 walls or “leaves” which act as an air barrier, meaning that, in theory, all the cold and rain from outside won’t come inside because there is a gap.

Can you guess what happens when you fill that gap with insulation?

When insulation is fitted, a team arrives and drills lots of holes in the wall  and then pump millions of tiny polystyrene beads, the same type that is found in a bean bag.

finding out if your home has cavity wall insulation

It is worth noting that on many surfaces, especially on render, the workmen will leave nasty scars on the wall which, unless you subsequently have the walls painted or coated with an exterior textured wall coating, you will not hide it with normal masonry paint.

Appearances aside though, if cavity wall insulating is a good thing, why does it cause damp in some homes?

Quite simply, this is due to exterior walls being in a poor condition, due to either a lack of maintenance, severe weather conditions, or more usually, the fact that the external walls have lost their weatherproofing ability.

When this happens, the water that rains on to your walls outside, gets soaked up inside the bricks.

This normally would stop at the cavity and would not pass into the house, although a good way to spot this is if your interior walls feel cold to the touch, even when the heating is on.

So the filling inside the walls starts to transmit the moisture to the inner leaf or wall, causing damp.

This photo shows the effects of wind-driven rain on to a wall with cavity insulation.

 

mould around window caused by cavity filled insulation
mould around window caused by cavity filled insulation

 

The walls on the house we used as an example are from a house that has had very little in the way of maintenance and as such the external wall surface soaks up water.

If the cavities had not been filled, the black mould around the window frame and the ceiling would not have appeared.

It is worth mentioning that if mould appears on your internal walls, this is a very BAD sign and we discussed at great length some time ago, how detrimental mould can be to your health.

Can having cavities filled cause any more issues?

Yes. Another issue that can occur is what is known as interstitial condensation which is when the inner leaf of the wall after insulation becomes much warmer (of course) and this has a knock-on effect of pushing condensation away from the inner wall.

This can cause condensation to form WITHIN the cavity because the dew-point, with warmer air, gets pushed back and out towards the cold outer wall, condensing and forming in the brickwork itself.

This problem comes into it’s own during winter time when the water now trapped inside the bricks actually freezes, expanding as it does, and forming cracks to the bricks.

Over time this can cause seriously expensive brickwork repairs, or in the case of smooth render or pebbledash, it can push the wall surface away from the bricks, causing what’s known as “hollow render” or “blown pebbledash”!

If a house has pebbledash on the walls, when it starts cracking, it can be difficult and expensive to fix.

Is my home suitable for cavity filled insulation?

Probably yes, but it very much depends on the condition of your exterior walls.

If the walls are porous and let in water, you could do worse than to consider having the walls done too.

If your house walls are weatherproofed with a protective coating, they won’t let the water in, so you won’t get damp, plus the installation of the cavity fill will be successful and you will benefit from much lower heating bills.

Be aware though that you need the insulation fitted BEFORE you have any further works to the exterior walls.

A textured wall coating will cover up the scars left, but normal masonry paint won’t, so bear that in mind.

So if I already have cavity filled walls and mould appears, what can be done?

Quite simply, some attention and care to the outside walls will stop any water from transmitting inside and the mould will go away.

There are two main products that we would recommend for this, and both are guaranteed to stop all instances of penetrating damp, even if the mould existed before the cavity walls were filled.

The first product, a resin based exterior textured wall coating which is a service offered by ourselves and includes a full repair programme to the walls, fixing cracks, loose rendering and so on.

It comes with a 20 year warranty, against a life expectancy of over 25 years!

If you look at our gallery pages (in the menu bar at the top of this page) you will see what a difference it makes to a home.

The second product we recommend is a damp-proof wall coating which is suitable for listed buildings, houses made from unpainted stone, and brick houses too, as it does not change the appearance of the property, but affords outstanding weather protection into the bargain.

If your home HAS suffered from mould, then it also best to rent or buy a dehumidifier, although you may need to use it for many weeks before any problems start to clear up.

If in doubt about any of the above points raised, then your local cavity wall insulation company should be able to advise you on what is best, although of course bear in mind they may not be so impartial as we are!

So in answer to the original question posed: Cavity wall insulation IS a good thing but ONLY if the outside of your house is correctly weatherproofed.

A wall which is exposed and gets “the weather” mainly wind driven rain is the most susceptible elevation of a house to experience cavity wall insulation soaking up rain water, transferring it into the home, and causing mould to appear on the interior walls.

To find out more, give us a call on 0800 970 4928 or click here to send us an email.

NOTE: We are not a cavity wall insulation company so don’t ask us for a quote for cavity wall insulation please! thank you

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