| | | FAQ's
(A) Is it serious
(B) How does it work?
(C) How do you fix cracks
(D) If it isn’t subsidence what could it be
(E) What’s it got to do with me
(A) Is it serious -
How do I know if my house has subsidence?
Will my house have to be underpinned?
Why do I need an engineer or surveyor?
What is monitoring and how long does it take?
Why do my trees have to be cut down?
(B) How does it work?
What is foundation underpinning?
What is the difference between mass concrete and piled underpinning?
What is soil grouting? (Ground improvement)
What guarantees do I get when my house is repaired?
(C) How do you fix cracks
What is crack stitching?
What is resin bonding?
What is EML?
What is BRE Digest 251?
(D) If it isn’t subsidence what could it be
What is thermal cracking?
What is roof spread?
What are wall ties?
Why do my doors and windows sometimes stick?
What is “historic movement”?
What are latent or inherent construction defects?
I have cracks in my walls but I have been told it is my windows. Is this right?
(E) What’s it got to do with me
My house is going to be repaired, why do I have to be “the employer” under the contract?
What is the Party Wall etc Act 1996?
What is CDM?
How do I know if my house has subsidence?
This is not an easy question to answer but typically, subsidence manifests itself as cracking in the external walls of the house. Subsidence tends to generate diagonal cracks (but not always) and such cracks are visible inside and out. It is unlikely there will be cracks only at first floor level. Subsidence cracks can often be followed down to ground level. It is rare for subsidence to generate just one crack in isolation, there will be other cracks and/or distortions.
Subsidence can also cause distortion of windows and doors but be careful because there are other factors that can cause distortions that look like subsidence but are completely unrelated.
Another problem is whether or not a crack in a wall is recent. All buildings move and crack. It is quite common for cracks to be identified when they have in fact been present for many years. Fresh cracks are characterised by having sharp edges and are not full of debris and cobwebs. Old cracks look dull and often have paint and old filler in them.
Be aware that there are many causes of cracking in buildings and only one of them is subsidence. If you are worried your house has subsidence get a professional opinion from a Chartered Engineer or a Chartered Surveyor.
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Will my house have to be underpinned?
Subsidence does in some ways have a very negative appearance in that most people believe it means your house HAS TO BE underpinned and that this will mean having to move out. This is rarely the case.
The whole purpose of further investigations, monitoring, dealing with trees and drains etc is to establish why a building has moved and to take away any identified external influences. Usually, dealing with trees and/or defective drains is sufficient to return stability and therefore, underpinning should not be needed.
In some cases, the results of ground investigations show adverse conditions or that tree removal is not appropriate and therefore, if there is no acceptable prospect for long term stability foundation underpinning will be recommended.
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Why do I need an engineer or surveyor?
Engineers and surveyors deal with the “nuts and bolts” of buildings. They investigate building problems, identify the causes and make suggestions as to how it should be fixed. In relation to Insurance Claims, they provide the technical support to Loss Adjusters who deal only with the insurance related issues.
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What is monitoring and how long does it take?
Monitoring refers to the measurement of cracks and distortions in a property to determine if structural movements are taking place. Typically, such monitoring is restricted to using tell-tales fixed across certain cracks in the walls. The monitoring usually starts at the time of a site investigation (but not always) and is usually left in place for not less than 6 – 12 months. Sometimes, the monitoring can take longer depending upon the circumstances and whether or not trees and vegetation have been removed and/or drains repaired.
Tell-tale crack monitoring uses small stainless steel discs and vernier calipers. The measurements are generally accurate to 0.01mm but a building is generally considered to be stable where variations in measurements are within a tolerance of 0.75mm but again, this is not applicable to all cases. Crack monitoring tell tales are usually read on a bi-monthly interval.
Level Monitoring is another method for determining if a property is stable or continuing to move. This technique in most cases can be done by simply taking relative levels around the damp proof course or other suitable feature that would normally be level all around the building (within acceptable tolerances). This type of monitoring is suited to measuring tilt and for preparing general distortion plans. Level measurements are not undertaken at the same frequency as tell-tale readings, often, 6 monthly intervals are sufficient but can be increased as circumstances dictate.
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Why do my trees have to be cut down?
The removal of trees in relation to cases of subsidence damage generally relate to areas with CLAY soils. Clays shrink and swell depending on how much moisture they have in them. Trees extract moisture and cause shrinkage, foundations move down and cracks appear. Very often, BUT NOT ALWAYS, removing the tree is an appropriate remedy. Taking the tree out enables the clay to take up moisture and the clay swells literally lifting the house back to its stating position (or at least close to it). Once this has taken place, the house should remain stable and foundation underpinning is not likely to be needed.
The other reason for removing a tree is that you may own a tree that is causing damage to a neighbours house. Irrespective of whether you would agree or not, you have a legal liability in respect of damage caused by trees in your ownership. Often you will be notified by an engineer/surveyor or loss adjuster that a tree or trees in your garden are causing damage. If you do not remove them or reduce them, the costs of repairing a neighbours house could be recovered from you and/or your liability insurers.
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What is foundation underpinning?
Foundation underpinning is defined as the downward extension of a foundation. Its’ purpose is to transfer the building loads to more stable soils that exist at greater depth. Depending on the depth required, and the extent of superstructure damage, foundation underpinning may be undertaken in the “traditional” form which is with mass concrete – typically, this method is used for smaller projects and normally for depths of upto 2.75m, 3.0m is unusual but does sometimes need to be done.
Where the extended foundation needs to reach beyond 3.0m, piling is the preferred method.
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What is the difference between mass concrete and piled underpinning?
In essence, mass concrete underpinning involves men digging under the house foundation and then filling up the hole with concrete. As the depth increases so do the difficulties and the risks. Mass concrete is not suitable in some ground conditions where it is only safe to use piling options.
Piling is a much more economical and safe method of providing deep foundations. In very basic terms piling is like banging a big nail into the ground and then attaching the house foundation to it. The methods for piling structures does vary and can be quite complicated. If your house is to be piled and you are unsure what this means you should speak with your engineer.
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What is soil grouting? (Ground improvement)
Where movements take place in sandy soils, the ground can be improved by grouting. This essentially involves pumping in a material (cement grout or special expanding polymer grouts) that binds the granular soil together and makes the ground stronger so it can support a building. The polymer grouts can also expand and are used to lift buildings back to level. Grouting is a specialist operation but it is very quick with minimal disruption but is only suited to a limited range of site conditions.
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What guarantees do I get when my house is repaired?
In most cases, where the repairs are restricted to superstructure crack repairs and redecorations there are no guarantees as such, however, Insurance cover is unaffected and if damage returns then your Insurance Company will reopen the claim depending on the elapsed time.
If the repair involves underpinning there should be a materials and workmanship guarantee from the contractor. Some contractors offer a limited insurance backed guarantee but this is not an absolute requirement.
Upon completion of repairs, the engineer should issue a letter outlining the nature of the problem , the investigations undertaken and the work that was done.
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What is crack stitching?
Crack stitching is a method for repairing cracks in masonry. In the “old days” crack stitching was done by removing cracked bricks or blocks and putting in new ones and then repointing.
To make sure the bond and integrity of masonry is properly reinstated, cracks are raked out and short lengths of stainless steel are embedded into the mortar to transfer load and stresses across the broken joints. The repair is simple and is well within the capabilities of a competent general builder.
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What is resin bonding?
Resin bonding is another method of repairing cracks in masonry. In very simple terms a special resin is injected into a crack and “glues” the wall together. This is a good method of repair where the circumstances are appropriate but should not really be considered in older properties that have old lime based mortars.
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What is EML?
EML stands for expanded metal lath. EML is used under plaster and render where it provides a good key for the applied surface finish, helps to control cracks and also provides additional strength across a repaired crack.
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What is BRE Digest 251?
The BRE is the Building Research Establishment. The BRE is a scientific organisation that focuses on all aspects of the built environment. The research that is undertaken is published in a variety of documents of which, the Digests form a principal source of information for surveyors, engineers, architects and contractors. Digest 251 “Assessment of damage in low-rise buildings” is essentially the yard stick by which the seriousness of cracking and distortion in houses is measured.
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What is thermal cracking?
Thermal cracking affects most masonry structures. All building materials move as a function of expansion and contraction caused by variations in temperature. These movements generate stresses within the materials. When the stresses reach a certain magnitude, the material cracks and effectively forms a movement joint to allow the expansion and contraction to continue.
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What is roof spread?
Roof spread is a problem where a cut timber roof becomes distorted because there are inadequacies in its design. Sometimes, roof spread happens because the roof covering has been changed from slates to heavier concrete tiles.
The simplest way to describe what happens is to consider an old style step ladder that has a chord to hold the ladder up. If the chord is cut the legs of the ladder move outward and it collapses. Roof spread is not a sudden event and collapse is very unlikely unless it is left for a long time.
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What are wall ties?
In a cavity wall, there are two thin skins of masonry. Older houses have two skins of brickwork, more modern houses a skin of brickwork and a skin of blockwork.
The two skins need to be tied together to give the wall structural integrity. The ties should be positioned at 900mm centres horizontally and 450mm centres vertically. The ties themselves were made from iron in early times and then out of galvanised steel. Corrosion of the ties has become apparent as have problems with an inadequate number of ties. Modern ties do not corrode, they can be made of stainless steel and plastic.
If there are insufficient ties or the ties have corroded, the wall becomes unstable and often cracks and bulges. The damage can look like foundation movement but is unrelated to the foundation.
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Why do my doors and windows sometimes stick?
It is true that building movement can be identified by sticking doors and windows as the openings distort as a function of structural movement but more commonly, doors and windows (timber) will stick due to changes in the weather. This might sound strange but timber is a remarkable material, it is sensitive to relative humidity and temperature and responds to its’ environmental conditions. Timer is anisotropic and has a high hygroscopicity (scary science!)
Anisotropic means the strength of the material is different depending on where it is measured (across the grain, parallel to the grain). Hygroscopicity relates to the ability to absorb moisture from the atmosphere. As a function of these properties, timber “breathes”, it shrinks and swells and warps and twists in varying degrees and it is this natural behaviour that often causes doors and windows to stick.
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What is “historic movement”?
Historic movement or more generally, historic damage is the term used to describe evidence of movement or distortion that happened some years ago. Historic damage will be things like old filled in cracks, distorted windows/doors, areas of repointed masonry. Such damage indicates a building has moved but is now stable and no further action is needed provided there is nothing to indicate otherwise.
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What are latent or inherent construction defects?
These are problems in houses that result from their design and/or construction. Typical examples of such defects include roof spread, wall tie failure, poor lateral restraint, calcium silicate brickwork, shrinkage of plaster, compaction of fill under solid floors. These types of problem are not generally covered by insurance.
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I have cracks in my walls but I have been told it is my windows. Is this right?
Absolutely. Where replacement windows are installed, the installers very often do not consider the consequences. Timber windows in many instances are actually load bearing, especially bay windows.
Replacement windows are not load bearing and if the installation is not correctly executed, structural damage can result. In extreme cases, it is not unknown for partial structural failure to result from a defective window installation.
Yes plastics window frames should be reinforced but this is to provide rigidity against wind loads not to carry structural loads. Also, replacement windows should have a gap all round to account for expansion and contraction, this often causes a problem that is simply “covered up”.
When replacing windows, there should always be a check carried out to ensure there is an adequate lintel support across the opening. In the case of bay windows, there should be a properly considered bay pole that MUST bear onto the brickwork (not the plastic cill!!) and then onto the structure above the head of the window (this could be brick or timber).
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My house is going to be repaired, why do I have to be “the employer” under the contract?
In very simple terms, as the home owner you want the repairs undertaken. For a contract to exist you have to have an offer from a contractor to do the work and acceptance of the price and the terms and conditions from you.
Essentially, you have to remember that although the Insurance Company provides the funding for work, you are the person asking for it to be undertaken. If you engaged a contractor yourself, you would be the employer, you might also have a surveyor or engineer to advise you. The situation is almost the same as part of an Insurance claim but you seek payment or at least reimbursement for the work undertaken from your Insurer.
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What is the Party Wall etc Act 1996?
The Party Wall Act is a piece of legislation that requires building owners to advise their neighbours of certain works that could affect a party or boundary wall or any building within certain distances of certain types of work. The Act confers rights to building owners and adjoining owners but fundamentally it seeks co-operation between parties.
Where works to a property fall within the Act, party wall notices are served. Provided there is agreement between parties for works to be carried out, the requirements of the Act are fulfilled, if there is disagreement, then the Act sets out the procedure to be followed to resolve any dispute. Accordingly, if there is a dispute, repairs to a property may be delayed.
The Party Wall etc Act 1996 also applies to such things as extensions and conservatories.
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What is CDM?
CDM is the Construction (Design and Management) Regulations 1994 and is more widely known as Health and Safety. The CDM regulations require designers and contractors to properly consider hazards and risks and then remove or reduce them as far as practicable.
CDM regulations place duties on clients, designers and contractors. For all projects, there should be an audit trail showing due diligence in the consideration of health and safety issues. Sometimes, a project may have to be stopped due to issues relating to health and safety where unforeseen circumstances arise. For a householder, this may cause frustrating delays but a short delay cannot outweigh the possibility of a serious injury or even death.
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