Unforseen Circumstances...

This survey concerned an old Weaver's Cottage which had had a damp proof course installed approximately five years ago.  It's consequences were obviously unforseen at the time, as was the 'improvement' of having a new floor laid!

Client(s) Ms DG

Property West Yorkshire

Instructions To inspect the property and report on any issues of dampness, timber rot or insect infestation

Background The client is purchasing the property and requires clarification on the above matters.

Disclosures I have no affiliation, financial or otherwise, with the client or the property.

Limitations Nil

Restrictions Nil.

Date of Survey   June 2005

Weather Fine

Viewing Orientation All observations are made as if looking towards the house from the front.

Type of Property A mid Georgian stone built terraced cottage under a stone slate roof. The property has accommodation on three floors with gas central heating but no double-glazing. I understand that it is Grade ii listed.

External Observations The property faces in a northerly direction and its walls are rubble filled approximately 600mm in thickness. The roof, which seems to be in good condition with sound flashings and guttering, was only visible from the front elevation.

There is no visible evidence of a damp proof course (dpc) but the present owner advises me that a damp proofing system was installed approximately five years ago. This was borne out by internal observations.

To the front of the property, the external ground level is higher than the internal floor level.

At the rear is a small lean-to porch, constructed of masonry with timber framed glass panelling. It did not seem to have any defects.

Pointing to both elevations was in good condition but it has been carried out using a sand and cement mix instead of a lime mix, as the original would have been.

Ground level to the rear is slightly lower than that of the internal flooring.

Internal Observations Second Floor:

This area has been created by utilising the original attic/loft space. It has the original oak Queen Posts and oak purlins, one of which has suffered badly from insect infestation and has been supported by the use of a further softwood purlin alongside it. Most of the timbers in this room show signs of moderate to severe infestation by Common Furniture Beetle (Anobium punctatum), also known colloquially as ‘woodworm’.

I did not detect any signs of ongoing infestation and the present moisture content of the timber would not normally encourage Common Furniture Beetle activity, also, there was an absence of frass, which is deposited by the beetles when they are active. All these indicators point to a cessation of insect activity on this floor. However, given later findings in the rooms below, this cannot be ruled out. In addition, one of the purlins (the second purlin from the front on the right hand side) has begun to crack. I cautiously tested the area of the crack with a screwdriver and it is apparent that it has suffered badly from infestation and is now quite soft.

The floors generally are in poor condition and seem to be covered with linoleum and boarding. Several of the original flooring planks I saw were split and also had signs of insect infestation.

First floor:

There were limited signs of infestation in some of the flooring timbers but, significantly, I found the bodies of several beetles. These I identified as Common Furniture Beetle.


Ground floor.

The ground floor is solid with a decorative laminate overlay.

On inspection it was noticed that the walls in this room have been re-plastered using a sand and cement render coat beneath finishing plaster. This is normal when an injection dpc system is installed. As I mentioned earlier, I could not see evidence of such a system on the external walls but this is not necessarily conclusive as any injection my have been into the seams and then pointed over.

Moisture meter readings indicated that the dampness is being managed and the surfaces of the walls provided acceptable readings. However, most of the skirting boards had high moisture content and are susceptible to rot and insect infestation.

The timbers on the window cill and also the timber linings over the mullions also had high moisture content and these too are susceptible to rot and infestation.

Visual examination revealed many insects, both dead and alive. These insects were Common Furniture Beetle and also Wood Weevil (Pentarthrum Huttoni). The presence of the latter insect is quite significant because its habitat is damp and rotting timber.

The two main structural beams in this room are oak and showed little in the way of insect attack.

There are newly installed kitchen cabinets to the right hand sidewall; these will not be in danger from insect infestation owing to the high chemical content of their constituent boards.

Discussion There are two main areas of concern in this property; the first is the dampness, which has been managed rather than cured, and the second, which is directly related to the first, is the insect infestation. It is unlikely that you will be able to do anything about the former and will probably have to accept the situation as it is, but the infestation and potential for rot to the timbers must be addressed.

When this property was originally built, it had the innate ability to rid itself of moisture by evaporation. This would have occurred from the floors, which would have been flagged, and also via the walls, which would have had lime mortar beds and lime mortar pointing.


At some time within the recent past, modern theories will have dictated that the floor should be covered, probably in an attempt to create an even surface or as a ‘cure’ for ‘dampness’.

Any ground moisture beneath the new floor cannot now evaporate because of these coverings (both concrete and laminated boards) and it is therefore seeking a route to the atmosphere via the walls.

At some stage these will have begun to show dampness and thus have been injected with chemicals and then rendered at their lower levels with a waterproof coating, such as sand and cement. This is a standard damp proofing system.

If the injection part of this system had been effective, then it may have contained the dampness but, because the walls are quite thick (600mm) and will have a rubble fill in the middle, this part of the system will be inefficient, indeed it may not even be working at all. The render coat will be keeping the surfaces of the walls free of damp but will be merely channelling it upwards via the rubble filled centres.

Consequently the extreme base and centres of the walls are still damp and the moisture within, at least on the rear wall, has risen in height to the point where it is now causing high moisture levels in the timbers of the window cill.

Eventually, equilibrium will be attained and the moisture evaporating from the external stonework higher up will match the moisture entering the walls from the ground. At this point, as long as there are no timbers involved, you should not have further problems (but see later note). In the meantime there is an issue with insect infestation and, although I cannot find any significant flight holes, the amount of beetles and weevils, both alive and dead, leads me to the conclusion that it is active in the damp skirting and window boards.

This property, having had a damp proof course system installed, will always suffer from dampness at the base of its walls where they are in contact with the floor. This is in the nature of such systems and there is little you can do about it without completely undoing earlier works and restoring the property to its original condition. This is not a practical proposition and consequently you need to ensure that the dampness does not cause problems of rot or insect attack in the future.
To do this you will need to remove the affected timbers on the ground floor and replace them with pre-treated timbers that are resistant to both rot and insect attack.

As stated earlier, the moisture content of the timbers on the second and first floors militates against ongoing infestation by Common Furniture Beetle; it certainly precludes an attack by Wood Weevil. However, given the obvious nature of the ground floor infestation by Common Furniture Beetle and the fact that beetles were seen on the first floor, to take the risk that the infestations on these two upper floors are now extinct would be unwise.

Conclusions You should instruct a BWPDA registered company to treat all timbers throughout the property for attack by common furniture beetle and other insects.

You should remove the skirting boards on the ground floor and replace them with pre-treated timbers to your own design specification.

You should remove all timbers from the window cill, reveals, head and mullions and replace them with timbers pre-treated as above. There will probably also be an oak lintol over the window and this should be checked at the time for both rot and infestation. You may need to refer back to me at the time.

It would be advisable to lower the ground levels at the front of the property to a depth of at least 150mm below the internal floor levels. A small trench, filled with coarse stone and gravel would be appropriate and this should then be maintained adjacent to this wall. Its purpose is to assist the lower walls to evaporate their excess moisture.

The defective purlin on the second floor should be supported by an additional purlin of suitable cross-sectional area. This exercise should be similar to that providing support to the purlin on the rear left hand side of the room. If you are in doubt as to the required cross section and/or methods of support, please consult a structural engineer.

N.B. You should also be aware that dampness in the ground floor walls may eventually rise above the level of the sand and cement rendering that has been applied as part of the damp proofing system. This occurrence is dependent upon several factors and may not even happen at all. In the future, if you notice damp staining approximately one meter above floor level then you should contact me again for further assistance.

I trust the above is satisfactory for your purposes but if you require further clarification please do not hesitate to contact me.

 
Surveyor Patrick F Doyle CSRT M. Inst. R.T.S.

Qualifications Certificated Surveyor in Remedial Treatments issued by the BWPDA.

Date of Report June 2005

Signed Surveyor