Archive for August, 2009

Aug 28

This 1976 brick built Dorset bungalow retained blown fibre insulation introduced in the late 1990’s.

Wall showing rain penetration

Wall showing rain penetration

Rain penetration penetrated the outer masonry and bridged the cavity causing internal decorative spoling and decay to skirting boards. Moisture entrapped within the cavity wall is clearly visible at DPC level externally and is aggravated by very hard impermeable motar.
Saturated perp end joint

Saturated perp end joint

The seriousness of this particular problem became apparent when drilling the perp end joints which were saturated.
Saturated motar between the brick work

Saturated motar between the brick work

Saturated mortar from between the brickwork.
Moisture squeezed from the insulation material

Moisture squeezed from the insulation material

Moisture squeezed from a sample of the insulation material removed.
Remedial costs to remove the insulation and make good, excluding internal repairs and redecoration, was in excess of £2000 plus VAT
Aug 28

Cavity Wall Insulation
(What are the benefits? …..…..DAMP)

From October 2008 all domestic buildings (being built, rented or sold) were required ‘by Law’ to have an Energy Performance Certificate (EPC) to help improve the energy efficiency of the building. The EPC provides an ‘A’ to ‘G’ rating for the building, ‘A’ being the most efficient and ‘G’ the least and to-date a ‘D’ rating is currently being banded as the average.

It is claimed that around a third of heat loss in a house is through its roof and walls and currently there is a government drive (supported by television advertising and the offer of Home Improvement Insulation Grants) to encourage home owners to increase loft insulation and also to fit cavity wall insulation, as it is claimed this can save on average around £180 per annum on heating costs!

However were you aware that by installing cavity wall insulation, whilst you may well be saving some money on fuel costs, you could also be creating a major expense for the future……..damp!

Example of cavity wall insulation

Example of cavity wall insulation

The cavity wall (as we know it) dates back to the early 1900’s and is commonly found in the coastal areas around Britain, used to reduce the risk of rain penetration. In the 1920’s, local building by-laws encouraged the construction of the cavity wall and by the 1940’s it had become the Industry Standard. The familiar cavity wall (as we know it) is two leaves of brickwork, forming a 60mm cavity and tied together with metal wall ties.

Even back in the good old 1970’s concerns were being expressed over Energy Conservation and home owners were then being encouraged to introduce loft insulation and it wasn’t long after that cavity wall insulation was also being recommended.

Fill your cavities with foam, polystyrene, mineral wool or any other material you can introduce through a small hole in the wall and you will save energy and loads of money. Sounds good, but what if by introducing this insulation you increased the risk of damp to your property, which in turn would cause internal decorative spoiling, plaster damage, fungal decay to  structural and joinery timbers and also accelerate the risk of corrosion to the metal wall ties.

Could that really happen? Well the answer is yes and it is.

Paul Carter, the principal of Premier Heritage, has investigated hundreds of buildings over the past 20 years of so, where damp has affected internal decorations etc and found that the damp present was due to bridging of the cavity by the earlier installed insulation materials. Whilst some of these cases were wrongly diagnosed by others as rising damp, most of these buildings (if not all) retained a physical damp proof course, the newest being a 1980’s brick built bungalow in Hampshire.

Ok, lets put this into perspective, there have been thousands of cavity built houses within the UK that have been insulated and a good majority of these don’t currently have nor will ever have a problem with damp. But there are a great number that have and no doubt more will be affected in the years to come! 

Increased rainfall in past years has resulted in a noticeable increase in damp problems affecting conventional cavity-constructed housing, due to moisture penetrating / bridging the cavities and in particular on the weather prevailing elevations and this isn’t a problem relating to current rainfall, but a gradual build of damp over many years.

Rainwater driving into the masonry of a building can penetrate the outer leaf brickwork leading to the wetting of the insulation materials, increased damp penetration and a reduced thermal performance of the material. Poor construction methods, mortar and perp joints, debris within the cavities, dirty wall ties and poor installation procedures by installers all contribute to the overall problem, which generally will result in the need to remove the insulation, which is not only expensive, but will almost certainly cosmetically scar the building when finished. Unfortunately it doesn’t come out through the same hole through which it went in!

So how do you avoid this problem? Well there’s no easy answer to this other than to look carefully at the building’s construction (porosity of building materials) and its exposure to the prevailing weather conditions. If having then decided to proceed, ensure that the chosen contractor / installer, during the survey, checks the cavities  and cavity trays for debris and dirty wall ties, but more importantly offers a system and material that guarantees (preferably insurance backed) that the materials being installed will not transmit / bridge moisture through and into the internal wall!

Alternatively, if you’re still unsure then don’t install.

Examples of Cavity Wall Insulation causing damp:

Cavity Foam Insulation

Cavity Foam Insulation

1970’s block constructed bugalow with poorly installed cavity foam insulation and debris bridging moisture via wall ties, cost around £800 to remove and rectify internal damage caused.

Polystyrene bead cavity insulation

Polystyrene bead cavity insulation

1930’s brick constructed house with polystyrene bead cavity wall insulation. Caused extensive damp to rear elevation walls, cost in excess of £3,000 to remove insulation and rectify internal damage.Polystyrene bead cavity insulation
Polystyrene bead cavity insulation

Polystyrene bead cavity insulation 2

1920’s brick constructed house, south facing elevation with polystyrene bead insulation and poor quality mortar. Caused extensive damp to internal decorations and accelerated corrosion of wall ties (rusting ends just visable), cost in excess of £3,500 to remove insulation and install new wall ties.
Aug 24

Damp and fungal decay survey at historic mill 

Premier Heritage are pleased to have been appointed to undertake Timber and Damp surveys of the former Tonedale Textiles Mill in Wellington, Somerset.

Tonedale Mill was established in 1790 by the Fox family and was, for many years, the largest integrated woollen mill in the South West employing around 2000 local residents. The original site extended to approximately 12.6 acres and provided a range of stone and brick built Grade II and Grade II* Listed buildings.

Tonedale Mill

Tonedale Mill

The Mill is of particular historic significance as it retains a full complement of buildings representing the complete manufacturing process, from processing the raw wool through to yarn spinning and the preparation of woollen and worsted cloths. During the Boer War the Tonedale dyers also developed the dye ‘khaki’ leading to the end of British soldiers’ “redcoats”.

Evidence also remains of the development of different forms of power generation: from the early water powered mill, to the steam powered mills and finally to the electrical generating complex in the centre of the site. The mills also had specialist buildings for the manufacture of metal and timber components for both buildings and machinery maintenance.

The property now benefits from detailed planning permission and listed building consent and Hydon ( www.hydon.co.uk )and their joint venture partner, Kenmore Homes, are developing in excess of 150 residential units and also commercial space, combining some minor new build with a sensitive conversion of the existing buildings, maintaining much of the original internal fabric.

As with many sites of this type, it has fallen into a state of disrepair and various buildings are now affected by significant damp ingress and varying forms of fungal decay, including dry rot.

Premier Heritage have been employed to initially undertake the timber and damp condition reports on the various stone and brick built buildings, which will include the inspection of over 800 original windows, all of which are to be completely renovated.

Aug 24
Wood wasp feeding on timber

Wood wasp feeding on timber

Although not strictly speaking a Heritage Survey, whilst undertaking a recent survey of a Edwardian house in Sussex, we were asked by our clients neighbour if we could take a quick look at and advise on a particular problem affecting her timber framed Conservatory.

 The conservatory which was situated on the side of a 1950’s bungalow was constructed in soft wood, although was not of particularly good quality or was it well constructed. Wet rot decay (white rot) was occurring to the lower frames and cills as a consequence of condensation running from the internal faces of the glass during the winter and soaking the timber. A 10 year guarantee was originally provided by the installer (a franchise conservatory company), although they had long since ceased trading.

Nothing unusual about that you might think, but the owner also pointed out that insect’s, described as ‘wasp like’ were also burrowing into the timbers.

The wasp in question, although not your normal Wood Wasp, was chewing quite happily through the apparently sound paintwork and

timber and within a matter of minutes (and long enough to take his photo) was up to his head and shoulders and well into the softwood frame.

Damage caused by wood wasp

Damage caused by wood wasp

After several attempts and about 15 minutes chasing the insect around the garden, it was finally caught and identified, as what was believed to be a Wasp of the genus specie ‘Ectemnius’. This is a Wasp that lay their eggs on paralysed flies, which they then store in burrows made in rotting timber, hence its interest in this rotting softwood conservatory.

We advised the owner of the conservatory that in our opinion the frames of the conservatory were considered to be beyond economical repair and removing the decayed timbers would remove the risk of further infestation by the wasps. Recommendations were made to have the frames fully replaced with a more durable timber, with suitable treatment and decoration.

  To learn more about wood wasps click here Below is a short video showing a wood wasp in action!

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