Sub floor ventilation, why spending a few pounds today could save you thousands tomorrow...

Often overlooked, sub floor ventilation is critical to the health of your home. If damp is at work, out of sight, under your floor boards, you could be accumulating a hefty bill that you could so easily avoid.

So let’s take a walk up to your front door and just see whether you’re harbouring a potential problem with your property.  First of all, what’s not original about your home? Has anyone added an extension, a new driveway or path? Are your borders raised with soil? Is there a car port, conservatory, porch or patio addition? Are there areas of decking or raised planters and flower boxes?  If so, the chances are that your air bricks which provide essential sub floor ventilation could be partially or completely blocked. 

Says Richard Walker, National Development Manager for Peter Cox Property Services, “It’s amazing how something so apparently small and insignificant as an air brick or two can impact on your home life so hugely.  I’ve even seen vents closed off deliberately with pieces of slate to ‘stop any draughts’ and others cemented over completely!

“But that’s precisely where all the problems start. Air bricks or air vents are normally fitted just above your property’s damp proof course and their job is to let air flow right through your property from front to back or side to side. This helps maintain the correct moisture level in your underfloor void.  Keep the moisture content to below 15% and you should be fine.  But once the level starts creeping up, then you can develop problems in the joists and floor timbers leading to, mould, damp, musty smells and eventually devastating Dry Rot.

“Modern properties usually have air-bricks spaced at around 1.5m apart but in older properties it can be very arbitrary, as can the size of the vents and what they’re made from.

“How are you to know if your sub floor ventilation is all it should be without a simple underfloor survey with a moisture meter?”

“These days”, says Richard, “as the water table is rising, and flooding more widespread, the problem really needs addressing early  - an ounce of prevention being better than thousands of pounds worth of cure. You can even help yourself by removing cobwebs, leaves and debris that can block vents. We’ll gladly show you how to keep them clear and clean with the minimum of effort.

So should you check your property’s sub floor ventilation?  The simple answer is yes. If you live in a home built before 1980, particularly in a pre-war, Victorian or even older home, it’s really worth a small investment now to have experts run a quick check for you. If your house is at pavement level, particularly in terraced properties, you really need to know what’s going on under the floor. If you notice your floors bounce, shift, creak or appear to be dropping away from the skirting boards – these are all tell-tale signs that the underfloor joists are already affected by moisture. Even if the problem is established, an early investigation can still help prevent it getting worse.

Says Richard, “Our inspections are hassle-free and don’t take long, although we do need to be thorough!  With the right meters, specialist know-how and equipment, the surveyors can be in and out in a very short time.  You will get a full report with any recommendations so you can breathe easy. I mean that quite literally. Diagnosing a damp or inadequately ventilated sub floor void early can actually help you avoid the mould and fungal decay spores which some people, particularly the young and old can be allergic to.

“If we do find sub floor ventilation problems, the reassuring news is that often we won’t even need to disturb your day to fix them. New air vents can be fitted from outside your property to achieve the necessary air flow and rectify your problem.  Where a property is at street level, we can’t lower the pavement but we can fit periscope vents to introduce air flow. Whatever solution we provide, it will be right for your property.”

Richard continues, “Recently, we worked on six houses near York racecourse, all of them affected by the raised water table and subsequently Dry Rot. Early detection in one house was key to the whole street agreeing to fix its mutual problem at source. The size and style of property isn’t the issue. The survey is similar wherever we go. It’s quick, easy and inexpensive so why wouldn’t you want to have your house checked out.

The fact is that you can protect your home and your family with just a little professional insight before problems have a chance to manifest.  You’re not only spending a little to save a lot, you’re also making one small investment to help protect your family’s long term health and well-being.

Depending on the circumstances, Peter Cox Property Services offer some surveys free of charge. The team will also consult for a quoted fee before you purchase a property, giving you extra confidence that you’re making the right move.

To discuss your property or to arrange a survey, please get in touch with your nearest office of Peter Cox Property Services at http://www.petercox.com/regions.php or you can also call 0800 789 500 to talk to the experts and we’ll send a surveyor with local knowledge of your area.

Timber Repairs - Rot Engineering

The repair of timbers weakened by fungal decay or insect attack (wood-boring insects such as woodworm beetles) is one of the important parts of a successful structural refurbishment exercise.
In some projects, repairs can be made so that chemical treatments can be minimised or avoided.

However, where structural damage has occurred timber repairs are essential.  Before commencing timber repairs and remedial actions to remove the rot and some types of beetle infestation, it is most important to eliminate the ingress of moisture and dampness. This is the primary method of control - together with promoting rapid drying of the structure. There are options for chemical treatment of course.

Procedures for timber repairs

There are various procedures for timber repairs. British standard BSS268 gives general guidelines. However specific information cannot be obtained in each case from the standard because of variation in construction details. An individual case will require detailed instructions from a structural engineer.
Before any cutting out of timbers is carried out the beams must be propped. Propping itself can be complex.  Anything other than simple single level propping requires to be designed. An engineer or competent scaffold contractor can usually help with propping design.

Epoxy resin repairs

These are a very useful way of repairing timbers. The technology has improved over the last 20 years.  Various methods exist for these repairs, increasing the scope for “keyhole surgery” procedures.

Basic splice repairs

This can be done bolting side by side or in line. The fixing method must result in a secure connection that can support the load and will not move in the future.

Dwangs (noggins) help prevent twisting of the repair. Roof joists should always be dwanged to prevent rotation. These should be located at the mid point of the bolt pairs. Too many splices in a line can produce undesirable bending moments along the splice line. To overcome this the fifth in each line of splices should run back to a bearing wall.

To splice timbers in thickness in excess of 150 mm it will normally be necessary to use steel plates, or some other system than a splice  An engineer’s detail will normally be required.

Beam replacement

Sometimes it is necessary to replace the entire beam. This can be done using a non-organic material like steel or concrete. Concrete can be used to replace Timber lintols over windows and doors. It is important to make sure that the bearing ends have secure seating. Some types of lintols have to be bricked up so that they can stand the designed loading.

Bearing beams may be replaced in steel. An engineer’s detail will design the steel beam. The beam must be securely mounted. If you are in any doubt at all about a repair get advice from a qualified structural engineer.

Steel plate or shoe connections may also be used. These can be made up to a specific design by a blacksmith, or commercially available plates can be bought from some specialist suppliers. 

For more information about expoxy resin repairs please click here.

Transfusion and Diffusion Damp Proof Course Systems

Peter Cox have been successfully installing remedial damp proof courses in buildings of all types since 1951. At that time Mr Peter Cox ran a stone restoration company based in London. He had noted that stonework at the base of buildings was often eroded as a result of rising dampness and he devised a method of retrospectively introducing a damp proof course (dpc) without significantly disturbing the wall structure. The newly installed dpc prevented further damage to the existing stonework and protected any new replacement stone at the base of the building. His original method of installing a dpc was known as the Transfusion system; this was patented, gained Agrément certification and has been listed as a valid method in BS6576 since the publication of the standard.

In brief, a silicon based water repellent liquid is introduced into the base of the walls via drilled holes which are normally into the mortar joint. The siliconate absorbs or ‘transfuses’ into the capillaries of the masonry; this lines the capillaries with a hygrophobic layer which resists capillary attraction therefore controlling rising dampness. The silicone material does not block the capillaries; the masonry can still ‘breathe’ and the wall structure remains fundamentally unchanged. The silicon water repellent used in the transfusion system is water based and non toxic; it is completely inert once cured and has no deleterious effect on the masonry into which it has been introduced .

Due to the installation process generally being via drilled holes in the mortar joint there is minimal disturbance of the actual stone or brickwork and once installed the holes can be re-pointed with negligible aesthetic impact.

Images showing installation of transfusion system and diagrammatic illustration of principle.



The transfusion system has been employed in thousands of prestigious and historic listed buildings throughout the UK and in other parts of Europe including Venice and Gibralter. Well known examples in the UK include York Minster, Selby Abbey, The Royal Mint, The Bishops Palace of Lincoln, Burleigh House Estate and Normanton Church.

Transfusion being used in a thick stone column of a university building.





Normanton Church – this ancient church was within the flood area of the proposed Rutland Water Reservoir. Prior to filling the reservoir the ground level outside the church and the floor level inside was raised by approximately two metres. A damp proof course was installed by transfusion above the new level to protect the stone walls from rising dampness in what were to become fairly extreme conditions.

Normanton Church after completion of the reservoir – the church is now used for exhibitions etc.

In 2002 Peter Cox developed the Diffusion system which was a natural progression from Transfusion. It is installed in a similar manner, the essential difference being that the silicon based water repellent material is now in a thixotropic cream form rather than a liquid. This allows greater control of the installation. Installation is via 10 -12mm diameter holes, which again, when drilled into the mortar joints enables a dpc to be installed with minimal disturbance and visual impact on the building, making it ideally suited to historic buildings. The water repellent material has no deleterious effect on the masonry. Installation of a dpc in this way prevents rising dampness and once dried down, damage to internal decorations is prevented and further damage externally from freeze/thaw is controlled.

Diffusion dpc installation.



Wood borer beetle (Ptilinus pectinicornis)

The Wood Borer Beetle (Ptilinus pectinicornis) is a small ‘woodworm’ beetle of the family Anobiidae, and is closely related to the Common Furniture Beetle. It produces holes that are similar in size, 1~2mm, with a talc-like pink or cream bore dust or ‘frass’ that is quite difficult to dislodge from the timber. The bore holes are numerous and close together.

Adult Ptilinus pectinicornis beetles are up to 3.5-5.5mm length. They are distinctive due to the highly developed antennae; eyes much larger in the male. The beetles have black or brown heads with a lighter body.  

Species attacked include hardwoods like beech, elm and willow.   Unusually, in addition to normal tunneling damage by the larvae, the adult female beetle actually bores into the wood. It is stated that the female, having excavated a brood chamber in wood and laid eggs, remains in the chamber to protect the brood.   Damage often originates in timber yards and the  'infestations' are not uncommon in air-drying timber intended for furniture manufacture.  A dramatic picture can be found here.

Woodworm Treatment

In this case the infestation may be remedied by insecticidal treatment, although in some cases it may be cost-effective to replace the damaged timbers. Consult a woodworm specialist to diagnose the type of woodworm infestation and the appropriate treatment. Peter Cox Ltd will send an experienced surveyor to visit your property. They will describe the potential woodworm treatment costs and alternatives. Please contact us by completing our woodworm enquiry form or by telephoning us on 0800 030 4701.

References:

THE MORPHOLOGY OF THE REPRODUCTIVE SYSTEM OF PTILINUS PECTINICORNIS L. WITH A NOTE ON THE TERMINALIA OF THE PUPAL ABDOMEN (COLEOPTERA: ANOBIIDAE) P C Gardiner 2009

BRE307 Identifying damage by wood-boring insects

Wall Consolidation/Stabilisation

Construction:  600mm thick stone walls.

Problem: The construction consists of an outer and inner layer of stone with random rubble infill. The outer layer is bulging away from the inner one.
Typical symptoms are pictured below including the appearance of a gap in a reveal where the wall has moved away from the window frame and internally where a gap has opened up between the wall and skirting. 

Wall stabilisation actions:  For this type of consolidation anchors are typically installed at the same density as for standard wall ties,at staggered centres.

Crack Stitching Project

Construction – Solid 225mm brick wall

Remedial action

Crack stitches are usually installed in every third or fourth joint (or as specified by engineer) as shown on the photo above. They are generally 1m long (ie to extend 500mm either sided of the crack) and, in the case of the Joint Remedial Anchor system, are installed 50mm into the joint.

Wall Stitching Project

Construction:

Brick cavity wall.

The problem/cause of cracking:

The front elevation was coming away from the building.

Wall stabilisation actions:

Anchors were installed in a staggered pattern (see diagram below) at one metre vertical centres.  The uppermost set of anchors is always installed approximately one metre below the top of the wall ie. there needs to be about a 1 metre weight of wall above the first anchor.

The anchor lengths are varied/staggered to avoid a concentration of stress in any one vertical line.

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