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Lateral restraint in old buildings

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Many older buildings were constructed of thick stonework and lime mortar. This lime mortar is relatively weak and would have been used primarily for bedding as opposed to bonding of the stone.

Lateral restraint was provided by the floor joists, roof and internal spine walls; the floor joists were normally built into the walls but the mortar would break down over time and the restraining abilities would be reduced. In some buildings, you might see restraint provided by buttresses. In modern construction, ceiling joists are mechanically fixed to the walls with galvanised steel joist hangers which provides greater stiffness to the building.

Cracking or bulging walls are the main sign of lateral restraint failure and this property in North Cork was suffering from serious vertical cracking along both gables. The opening up of previous repairs suggested that damage was progressive with movement being compounded at one gable where the stairway was located.

Unfortunately for Substruck, this cracking is not foundation movement related. Remediation should primarily focus on the root cause as opposed to the affects. There are several solutions to arrest the movement; a more traditional approach would be tie bars with pattress plates installed to both elevations to provide enough restraint. These ties may be installed parallel to the floor joists at first floor level.

If you have concerns about any type of cracking, please drop us an email with some photos on info@substruck.ie.

Splashing in Glasheen

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The location of access points, relative to soil pipes, needs careful consideration during design and construction. Soil pipes and direct connections from WCs discharge to much higher velocities than gullies and whilst carrying solids, pose a much greater risk of deposits accumulating within the chamber due to splashing and thus causing blockages. Furthermore, as some of the discharge to any drain will always be forced upstream, the risk of solids accumulating in the channel must also be considered.

Although Technical Guidance Document H – Drainage and Wastewater Disposal of Building Regulations 2010 recommends that a foul wastewater system should minimise the risk of blockages, it does not provide any further guidance on addressing splashing. In the UK, the NHBC (National House Building Council), the UKs version of Homebond, offers some guidance on the matter.

The NHBC recommends that the primary channel entry connection is used for all high velocity discharges and in some cases in conjunction with swept or long radius bends. However, they refer to the design of the connections rather than the location of the access point itself.

Anyhow, such guidance has not been applied at this property in Cork City and although there are items that should not be entering the drainage system, the result is splashing and the accumulation of deposits and persistent blockages. The only course of action is to change the layout of the drainage locally with respect to the above guidance.

Rubber seals in Mid Cork

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Leaking drains in UPVC pipework is normally attributed to poor workmanship and poor supervision. One of the most common defects associated with such leakage is related to the rubber sealing rings or the absence of.

There is always anecdotal evidence of construction workers removing the seals prior to installation as this accelerates progress on site. Such seals have to be carefully cleaned and lubricated before installation and tested to ensure that they are in fact watertight. During subsidence remediation works at this property in County Cork, we observed numerous seals deposited in the excavations during the original drainage works.

Under normal working conditions such defects may not contribute to significant leakage but however, in the event of a blockage, can readily allow exfiltration for long periods before becoming noticed by the homeowner. The ability to withstand such pressures is one of the primary reasons why drains are tested in the first place.

Wavin pipework was considered the ‘crème de la crème’ of UPVC drainage for many years. The fittings were provided with fixed sealing rings which could not be easily removed or dislodged during installation and the triple seal provided great tolerates to deviation in trenches. However, with the onset of the last recession, these premium fittings have been phased out in order to compete with other brands. The existing brand, known as the economy fitting, the name of which speaks for itself, is no where near the standards of the premium fittings. Extra care is required for such fittings.

Whatever type of fitting we use at Substruck, every piece of drainage is carefully installed and tested during and after installation. Our final tests are always a formality for the many professionals we work with every day.

How much does it cost to underpin a house???

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Sometimes we are asked about the cost of underpinning a house, but we are provided with very little other information. In some instances, when we survey the property, the damage is in fact not subsidence related.

The cost for underpinning a house will be dependant on many factors such as the type of construction, ground conditions, extent of damage, etc. There are so many variables that need consideration it is not always possible to even provide a ‘ballpark’.

In order to provide a firm quotation, we would need some if not all of the following information: structural survey, drain test report, specification and / or ground investigation report.

In most cases, subsidence works will be covered by home insurance, assuming that the sum insured is adequate. However, a policy excess will normally apply which may be in the region of €500-€1000.

Of course, you won’t get any joy for the stress you may suffer due to the long time it may take to settle a claim. This type claim can be very complex and requires different professionals of various disciplines to represent both the insured and the insurance company.

If you do suspect subsidence, the first thing you should do is contact Substruck and we will take it from there. Being there from the start allows us to build up a rapport with our clients and we are never more than a phone call away to provide the necessary advice and support.

Escape of Water in Co. Kilkenny

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In most instances, damage to a property from escape of water will occur slowly over time. It is in fact very rare that damage will manifest itself in a more sudden manner. Generally, such damage is related to a water supply leak where the volume of escape is much more greater.

And this is the case for this property in Co. Kilkenny where a ‘sink hole’ and other structural damage occurred overnight due to a leaking water supply. A mains water supply was running through the rear extension and a leak had occurred on the saddle connection between the water main and the service pipe. The leak was repaired and the area made safe by a contractor working on behalf of the utility provider.

The damage to the property was extensive, particularly in the vicinity of the leak. Category 3 cracking, doors and windows sticking and floors sloping were all evident. Notwithstanding all that, damage to the extension warranted a complete rebuild. The requirement for demolition in subsidence claims are extremely rare.

Substruck Ltd. was employed by the insurance company to design an underpinning solution to address the damage. Site investigation was required which included trial holes and ground investigation in the form of dynamic probing.

The proposed solution was a micropile supported raft needled through the rising walls of the primary structure. This would protect both the walls and floors of the property. And the rear extension was to be provided with a new micropile supported raft foundation.

Drains v Sewers

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‘Drains and ‘sewers’ are terms used interchangeably in the industry; however, by definition, they are very different. Simply put, a drain is privately owned and a sewer is owned by the State.

Since 2014, Irish Water is now responsible for wastewater (i.e. foul water), although surface water remains the responsibility of the local authorities. Up to 2018, for estates taken in charge, a private drain remained private up to the public sewer, regardless of where the drain was located.  Therefore, the responsibility for that drain rested with the homeowner. If the drain was served by more than one premises, responsibility was shared on a pro rata basis. In the UK, assessing responsibility is much more complex.

So if a homeowner wanted to replace this drain due to simple wear and tear, they would have to employ a civil engineering contractor to obtain a road opening licence from the local authority and complete the works.

However, since the amendment to the Water Services Act (2007-2017), for estates taken in charge, a drain becomes a sewer as it enters public property and is no longer the responsibility of the homeowner. But if that drain enters another private property, responsibility remains with the homeowner and not the neighbour!!! Access to that property to maintain your drain is provided under the Land And Conveyancing Law Reform Act 2009. But if in the event of an estate house which is not yet taken in charge, responsibility will remain with the householder.

Therefore, Irish Water is now responsible for the pipework from the boundary of the property .

Great news for homeowners – bad news for the taxpayer!!!!

Lead Pipe Pitting in Blackrock

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Water supply leaks can cause significant structural damage to properties, even over a short period of time. During a subsidence investigation at this property in Blackrock, Cork City, a private shared lead water supply was found to be the cause of the problem. Damage was noted as Category 2 cracking and enough distortion to render two doors permanently closed.

The leak was repaired and on inspection a hole with a diameter of 5mm was identified!!!!! This would suggest that the leak has been occurring for quite some time and the quantity of lost water must be enormous. The problem with old shared water supplies (which sometimes run to the rear of terraces) is that many are not provided with water metres. And therefore, leaks are more difficult to identify.

Lead has been used in domestic pipework in some houses up to the 1970s and the health effects are well documented. Irish Water estimate that about 180,00 homes and businesses are still being serviced by some degree of lead pipework.

The majority of lead water supply is inside private property which in theory places the onus of repair on the homeowner or homeowners. Irish Water offers a lead pipe replacement scheme which will replace any public side lead service connection pipes free of charge to customers if they have replaced the private side lead supply pipe. And grants are available to homeowners in certain circumstances.

At Substruck, we have been repairing and replacing all types of water supplies since we began trading in 2003. If you think you may have a lead supply and are interested in addressing this, please contact us for further information.

Tilt in Galway City

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There are many anecdotal guidelines to when one should become concerned about a crack. The width of the crack is only one aspect of crack interpretation and even though you might not be able to put your hand through it, if you see daylight on the other side then its certainly time to become concerned. 

The cracking on this blog is as a result of an extension built on a raft foundation in Galway City about ten years ago. The extension is rotating away from the original dwelling. It is in fact ‘tilt’ where the foundation or building moves as one unit with little or no cracking or distortion on the extension itself. Factors that influence the ability of a structure to tilt are the geometry of the building and the reinforcement of the raft. And of course, the ground conditions.

Tilt is normally expressed as a fraction and research by the Building Research Establishment have provided guidance on indicative values from where a building becomes noticeable (1/250) to where monitoring or remedial action (1/100) is required.

In this instance, a trial hole revealed that the raft was built on fill which was poorly selected and placed. Unfortunately, there was no supervising engineer employed for the works and the builder was allowed to design and construct the foundation himself.

Made Ground in North Cork

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The term ‘filled ground’ is used loosely in the construction industry but it has a very specific meaning. BS5930 Code of Practise for Ground Investigations defines such ground as that ‘in which material has been selected, placed and compacted in accordance with an engineering specification’. Ground that that has been simply filled without any engineering control is termed ‘made ground’. Both types of ground are generally termed ‘anthropogenic’ as man has had an influence over both.

In most instances, anthropogenic soils derived from sampling or trial holes can be easily identified as either filled or made ground. And this is certainly the case at a property in North Cork where made ground was identified as the culprit to foundation movement in a residential property. Although the soils are clearly re-worked, a few bottles here and there prove that the soils have been made up with little or no control.

Dynamic probes show that the soils were poor to depths of 1.5m to 2.5m with refusal encountered at about 3.5m. Considering that the foundation was constructed to greater than normal parameters, it could be the case that the builder / engineer on site increased the dimensions to compensate for the poor soils. Nonetheless, it didn’t work and the proposed solution is a combination of raking micropiles through foundation and ground improvement.   

Masonry Arching in Co. Laois

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The ability of masonry to arch (or ‘self-arch’) relates to the transfer of axial loads above openings to either side of the wall and is considered during lintel design. The term comes from the principle of how an arch works although there is in effect no arch (if that make sense).

For arching to occur, the main criterion is the presence of sufficient masonry above the apex of a 45° isosceles triangle, formed above the opening.  Other factors include the bond pattern, location of movement joints and the ability of the masonry on either side to carry the loads.

In underpinning works, the arching action of masonry is considered when specifying centres of needle beams in micropile supported raft foundations and traditional pile and beam systems where beams are to be installed through rising walls.

However, foundation movement to the order of about 50mm has rendered this garage wall in Co. Laois cantilevered along a combined length of about five metres and defying the laws of gravity!!!! The walls are constructed of cavity block in the normal overlapping bond pattern with no opes or movement joints to limit a uniform load distribution.

Ground investigation showed that the building was partially constructed on made ground to a depth of about two metres. According to the homeowner, this area was made up during the construction of the primary dwelling with little or no controls in place. The surface water system was also poorly installed and contributed to the movement.