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Thursday, 26 March 2015

Damp proofing a typical Welsh terrace wall

Typical streetscape in Cardiff
Can you stop stone and brick walls from getting damp?

The simple answer is YES, but there are a range of issues surrounding the question and the answer!

The main issue around whether a wall is damp or not is that diagnosing damp is an art not a science per se. Common damp meters use electrical resistance to measure damp and this is fine for timbers, but for walls it requires a lot of interpretation. High readings can come from salts in mortars, old lead based paint etc, so not always water. So where you take measurements can radically affect the advice that you are given. So some companies who are trying to sell you damp proofing measures can use these meters to show that you need treatment when you might not.

So that's the issue with defining whether you have damp, but assuming that you do actually have a damp problem the next issue is where is it coming from.

We have all heard of rising damp, but many houses in Wales suffer from penetrating damp. This is water that is blown, or diverted into the structure. This can be through cracks in pointing, cracks in render, leaking rainwater goods, blocked guttering, failed seals around doors and windows, ...

Damp can also be caused by condensation. This might be due to poor heating, ventilation, high humidity from indoor activities. Again this needs to be assessed by looking at heating and ventilation strategies and infrastructure. Do the windows have trickle vents, have the chimneys been blocked??

Rising damp might be due to a range of factors including external ground levels, the presence of replacement concrete floors, blocked under floor ventilation, ... 

As you can see, damp can be difficult to diagnose. However, it is really important to ascertain where the source of any unwanted water is coming from.

Once you know what the problem is, you can start to find the cure. However, the cure will be influenced by the history of the building and the materials that were used to built it in the first place. This means the make up of the basic structure and also the materials used to repair, maintain and develop it over time. This building pathology work is key to refining the diagnosis and will hence help lead to an appropriate solution being found.

I cannot go into any great detail here as each building is different and requires specialist individual advice. However, the question was is it possible to damp proof these old buildings. The answer you might remember was yes, so what are the solutions?

1. Rising damp

If you do indeed have rising damp then you might need to:
  • Lower the external ground level
  • Re-instate ventilation under the floor boards
  • Remove cement render from the outer walls
  • Re-point the bricks / stone with a lime mortar
  • Re-render using a lime render
All of these are potentially permanent solutions, however they are fairly major bits of work, so most people just want to inject something into the wall. This is potentially possible and it depends on a range of factors, one of which is whether the wall is made from solid brick or stone. These walls are fundamentally different in their nature and it is easier to apply modern injection treatments to brick walls. 

Damp that is rising in a brick wall can be treated quite effectively using creams like DryZone. However even here you see companies injecting the damp proof cream into the bricks rather than the mortar. So with care this type of product can be part of a solution (but not if your damp is due to condensation or penetrating damp). However it won't work in stone walls (unless you have an even mortar bed at the correct height - like in ashlar walls).

Stone walls are fundamentally 'moist' in nature and so need a more holistic approach that is based on material science. The solutions here are much more likely to follow the bullet pointed measures above. It might also need to be combined with addressing ventilation issues, as stone walls need to dry out by the movement of water from the water to the outer and inner surface. 

2. Condensation

This tends to be more due to high humidity in the building and so a balance needs to be found between energy efficiency, ventilation, insulation and behaviour. It may be that a house needs positive input ventilation, or that the old chimneys need to be unblocked and vented, trickle vents on windows need to be opened, humidity controlled extractors fitted, or just a clothes dryer installed in the garden / room with an extractor fan. 

3. Penetrating damp

Penetrating damp is generally caused by issues around poor maintenance of a property. However, it can be down to the use of inappropriate materials like cement render. Seals like silicon around doors and windows fail over time and rainwater runs down the surfaces and straight behind the sill. Cement render (is fundamentally inappropriate, but nevertheless covers the majority of stone and brick houses) cracks due to its brittle nature and traps water behind it. Gutters and downpipes need to be clear otherwise they can easily poor high volumes of water against (and into) walls. Poor drainage around the building can lead to water sitting against walls,  I could go on.....

As you can see, diagnosing damp and finding the correct solution is a bit more involved that just pumping in a load of chemicals. However, pumping in chemicals and using water proof cement is what we do in the UK to the vast majority of our solid walled houses. In fact many mortgage lenders insist on this type of damp treatment. What a shame, it is generally a complete waste of money and resources. A typical damp treatment costs around £4 to £5,000. Don't be fooled by guarantees and assurances, many are meaningless. A recent customer had a injected DPC installed and when it failed dismally she was told that it had been installed correctly and so she couldn't claim against the warranty!

We would always recommend that you use your money wisely and this means that it is better to find a permanent solution to damp. This requires time and knowledge to get to the correct diagnosis, It is not a quick trip around with a damp meter and a bill of £5,000. The answers are there, but you will generally need some independent guidance to find the right ones for you and the house.

Friday, 20 March 2015

Chimney Problems and Solutions

Chimneys are a potential source of water ingress and it is quite common to find damp areas around the chimney breast. So what's going wrong?

Well there are a few key factors to bear in mind.

1. Failed pointing. This is quite common as the chimney gets a lot of wind driven rain and this can easily get behind the mortar if cement has been used and where the old lime mortar has been eroded away. When repointing remember to use a breathable mortar (a lime based one). Whilst this does allow moisture into the mortar it also allows it to dry out again. So ensure that the mortar joints are scraped out (to a depth of twice the height of the mortar bed) and then get it moist and repoint using the lime mortar. This should be finished in a flush manner to the bricks. Make sure you replace any broken bricks as well.

2. Cracked flaunches. Flat surfaces are not good for waterproofing as rain can settle onto the flat surface and soak in. Maintaining an angle / slope on the flaunch is really important if it made from a porous material. Cracking here is very common (again when cement is used), so either use a lime based mortar (and paint it with a mineral paint for a long lasting breathable finish) or look at a replacement option with a impervious capping material. This will help to reduce any water ingress into the stack.

3. Chimney pot not covered. Cowls are really important as we need to stop rain water getting into the main structure. Depending on whether the chimney is being used or no, there are a range of options to help reduce the amount of rain that are able to enter the pot.

4. Flashing. It is quite common for flashing to be fixed with cement. This again cracks easily and hence should not be used. Flashing needs to be set into the brickwork properly, not just abutted to the chimney. The flashing should be a lead one rather than the modern 'fix' that is glued on. Where mortar has been used, again it should be a lime mortar should be used rather than cement.

5. Vegetation growing out of the stack. Roots from plants like buddlia allow moisture into the structure and so these must be removed and the resultant holes filled with lime mortar.

I would warn against using cement renders, water proofing paints etc as they are much more likely to trap moisture behind them in the long term due to the effects of wind driven rain. So using materials that breathe and also have some movement potential in them makes them more suitable for these high exposure elements of our homes.

If the chimney has too many problems to mention (and this can happen when cement renders pull off the finish on bricks) then you may have to render / re-render them. Oddly enough I would recommend the use of a lime render. Make sure that the render has a good cap though as even lime renders require protection from above, so the flaunch /capping is really important to get right.

Thursday, 19 March 2015

Passive House Retrofit

From Bere Architects
Passiv Haus is an excellent German energy standard for building new homes. It is a system that relies on making houses really airtight and insulating. Insolation then provides much of the heat energy for the house. Fresh air is supplied via a Mechanical Ventilation Heat Recovery (MVHR) system. This means that it extracts the stale moist air and uses this to preheat the incoming fresh air. This keeps heat loses to a minimum and hence means that heating bills are virtually non-existent.

Designing for this system to work in a new home requires the use of a spreadsheet called the Passiv Haus Planning Package (PHPP). Using this accurate system one can design a building with a primary heat demand of around 15 kWh / sq m per annum. This compares to a new building in the UK that complies to the latest building regulations, that will have a primary heat load of around 85 kWh / sq m per annum. So this means that Passiv Haus is around 9 times more efficient than a modern house.

But is it possible to make an old house into a Passiv Haus? Well, not even Passiv Haus Institute think that this is really possible, however the basic principles can still be applied. So they came up with the EnerPHit standard. The EnerPHit standard relaxes the requirement down 25 kWh / sq m per annum. So still about a quarter of the primary heating energy of a modern new build.

Sounds impossible? Well for many houses I think that it is impossible, especially where you are dealing with old solid and breathable walls. The risks involved in this type of construction are really too great to seriously contemplate, although there are people who have attempted it. The risks associated with 'deep retrofit' and the use of high performance materials when one is exposed to a fair amount of wind driven rain, increase to an extent where the whole project might be compromised and hence and savings would rapidly disappear.

There are houses, though where this 'deep' EnerPHit retrofit is possible. Most typically this is where you are starting with a modern cavity walled house. Here the materials used and the basic philosophy can overlap with the Passiv Haus concept. However it is still a mammoth task to upgrade a house from 120 - 150 kWh per sqm per annum down to around 25.

To undertake an EnerPHit project one has to have a real drive, vision and passion. A long term commitment to a house is also needed as it takes a while for any savings to start to pay back the capital outlays.

Personally I think that whilst the carbon savings are huge and hence it is absolutely the right thing to do for the planet, most owners will be doing it to get different types of satisfaction. Things like 'better internal environment', 'feel good factor' and 'future-proofing ones energy bills' will be more like the real driving force rather than purely an economic one.

The costs involved has meant that many of these EnerPHit projects have been either done as demonstrations, or by people with too much money on the SE of England. However, we do have a pioneer in Cardiff. To get a glimpse of the work that has been undertaken have a look at this amazing blog.

EnerPHit is not for all, but certainly there are huge advantages in doing retrofit properly and well and having the discipline of EnerPHit can be key in this. For more information have a look at the Passive House Trust website

Thursday, 12 March 2015

The failure of ECO

From Nick Heath / English Heritage report
A great report by Nick Heath for English Heritage is available that looks in detail at the issues raised by large scale retrofit. There are a number of horror stories there waiting to happen, but at least Nick has managed to create a guidance tool for local authorities to help them get over the many issues associated with these large scale 'improvement' projects.

One of the main troubles with ECO funding for External Wall Insulation (EWI) is that they only cover insulation measures. Nothing else. This means that lots of practical issues are not addressed. For example in the picture the insulation could not be fitted behind a lamp post because there was no money to move the post. This meant that there is a huge thermal bridge in the wall. This then causes a range of problems with damp, condensation etc and also means that there is a large impact on the effectiveness of the insulation.

I was in the SE Wales valleys last year doing some training for CITB on pre 1919 buildings and the same was happening there. ECO would not pay for roofs to be extended to provide the required protection for the insulation. So instead the contractors were required to install some plastic caps over the insulation. This relies on mastic / silicon sealant to provide long term protection from water ingress. The insulation system is therefore not guaranteed as it is not fitted to the manufacturers specification. The caps were supplied by other people and so there is a huge issue of future responsibilities when the water gets behind the insulation.

I feel sorry for the organisations installing ECO as they want to do a good job, but the ECO funding means that they just don't have the resources to do it properly. Of course the owners of the houses could pay for the work, but the whole idea behind ECO is that it is for those people who are disadvantaged and hence don't have the thousands of £s required to make up the shortfall.

One gets the feeling that many of these large scale EWI will fail and then cost an arm and a leg to put right. So in our drive to save carbon we are in fact probably going to end up having to pollute more. What a shame.

There are ways of doing this work at a lower risk, but it does cost more and requires a more skilled workforce. In the end, though, it would save more money, but the systems that the industry is forced to work to means that this will not happen. We will continue to have schemes that are underfunded, ill specified, done poorly (due to inadequate underpinning knowledge of materials and thermal dynamics) and also done at the wrong time of the year (most of the ECO work is done between November and March due to funding requirements).

A tad depressing, but I think that we need to know the issues so that we can try to ensure that we stop making the same old mistakes.

Wednesday, 4 March 2015

Shabby Chic

shabby chic coffee table with drawers

Shabby Chic is a great style for the environmentalists in the world. Taking second hand furniture and giving it a new lease of life is advantageous on a number of fronts:

1. It saves serviceable goods ending up in landfill / recycled

2. It provides a new market for those community groups who collect and sell second hand furniture

3. It creates value for goods that might otherwise need seen as rubbish, thus promoting re-use

4. It gives rise to creative thought and processes

5. The best materials for undertaking restoration work tend to be natural (like the excellent clay paints and waxes from earthborn)

6. It allows people to create fashionable spaces cheaply, thus helping to remove the pressure to spend on expensive items

So all you 'Shabby Chic'ers, keep up the great work.