Cracked Walls

It’s the dread of every house owner and one of the key defects a surveyor will be looking for when inspecting a property. Fortunately the presence of wall cracks is not always a sign of significant structural defect and following diagnosis may simply require re-decoration using flexible materials. In other cases, cracks can signify more serious problems or, in the worst cases, be the first sign of pending structural failure.


‘Crack Reading’, is a skill perfected by Building Surveyors and Engineers, both through technical training and through experience of dealing with many structurally defective properties. The ability to understand the make up of the underlying structure also helps the surveyor to diagnose the cause and severity of the situation while suggesting what might be done to reduce or eliminate the problem.


What causes cracking?

There are numerous factors that may result in cracking to the surface wall finishes of a building, from serious underlying structural defects, to minor materials shrinkage. Some cracks may be almost identical to others in surface appearance, while the underlying cause may be very different. A Building Surveyor will take all available evidence and circumstances into account so as to differentiate one possible cause from another. Identifying the cause is THE most important factor when it comes to later choosing solutions. If for example a diagonal wall crack was caused by seasonal shrinkage and heave of the ground, a flexible filler might be chosen to cope with movement and reduce the visual problem. If the crack has however been caused by an earth tremor, or mechanical impact, it might be appropriate to literally stick the structure back together with a rigid resin or ‘stitch in’ with metal ties. Wrong use of the resin or stitching for a crack that seasonally moves, could result in additional stresses and cracking to other elements, while using the flexible filler in the wrong situation could result in collapse e.g. the next time a tremor occurs.




Most cracks are a result of one or more of the following:-

-         Insufficient or uneven support (e.g. poor substrate or foundations)
-         General substrate movement (e.g. on friable steep slopes)

-         Unilateral pressure (e.g. from retained ground or expanding substrate of different moisture content or temperature). Frost heave can even be an issue in Spain on high ground.

-         Isolated reduction in support, e.g. through water related soil erosion.
-         Isolated pressure/ heave e.g. from tree root growth
-         Thermal expansion and/or contraction
-         Differential movement between materials or building elements
-         Redistributed loading (e.g. from a failing roof or floor), new works (e.g. an extension), adjacent excavation etc.
-         Mechanical damage, e.g. through impact (from a vehicle, slammed door etc) or seismic activity (common in Spain).
-     Shrinkage of materials

-         Use of the wrong or poor quality materials



How big does a crack have to be before it is  serious?

Unfortunately, any crack could indicate a serious defect, even if it’s hairline. It is generally the direction of the crack, it’s position within the structure and it’s rate of progression that will have a bearing as to whether or not it is serious. For example, block line cracking on an outer wall may simply indicate a poor paint system, depending on its pattern, while the same width of block line crack (of a different directional nature), could for example indicate the initial stages of subsidence.

Fortunately, hairline cracking is a typical initial indication of a problem that may be relatively cheap to remedy if caught early. Larger cracks may indicate a more advanced stage of failure, which invariably means more costly remedial works. If a crack appears suddenly, or gets worse very quickly it may well be serious and must be checked!

Horizontal, Vertical, Diagonal – Which are serious?

The crack direction will form a major part of the diagnostic process, but a crack in any direction could be either superficial or more serious. For example a horizontal crack could simply indicate differential thermal movement between underlying elements of the structure (not serious), while a similar looking crack could indicate foundation movement, or the eminent failure e.g. of a retaining wall (potentially life threatening).


How are cracks remedied?

Once the nature and cause of the cracking has been diagnosed, suitable remedial works can be specified. This may range (for less serious defects) from a simple re-paint with 100% acrylic paint, to physical bonding with specialist epoxy resins, filling with flexible sealants, mesh reinforcement, and sometimes use of more expensive but highly durable and flexible paint or acrylic mortar systems.


More serious structural defects could require underpinning, buttressing, carbon fiber/Kevlar bandaging, re-building of the affected wall parts, renewal of other elements (that have caused the cracking) e.g. a defective roof or floors or even demolition (if the building is dangerous or repairs are financially unviable).


Are older buildings more at risk? Are new buildings safe?

Not necessarily! While some very old buildings may be at risk of collapse, many have stood the test of time and may be structurally more stable than a brand new house next door. While some newbuilds are built to very high standards, with the correctly designed foundations and good substrate support, others may be seriously under-designed and sit over made up ground, shrinkable sandy clays or ground water courses (lack of adequate control in Spain, means that many newbuilds are under-designed and/or under-built).


Historically many houses were built by Spanish owners to then live in, so those that new what they were doing made sure they built well (local builders for local people also sensibly preferred to keep a good local reputation). Others were built with all good intentions by people who had no idea about construction. Nowadays newbuild housing stock may be built to live in by experienced builders or novices, most new houses are however, commonly built to sell on for a profit. It’s the effort to increase profits in the short term (by less conscientious developers), which has resulted in many defective structures. While not all are a risk to health and safety, cracks in buildings (even if repaired) can have a serious detrimental effect on their investment potential, for example an underpinned house will normally be far more difficult to sell on than one that never required such measures in the first place.




Every building is different and I have witnessed serious structural cracks in both new and old properties, from  newbuilds that have not even been completed, to houses that seem to have faired well for the first few years and others that may be hundreds of years old.


What should I do if my house has cracks?

Invariably I find that the cracks I have been called out to inspect are not the cracks that need attention. Many people over worry about superficial cracks while others fail to notice crack evidence of more serious issues. It’s certainly not worth loosing sleep over and if you are concerned about any cracks on your property it’s probably well worth getting them looked at by a professional. Houses do collapse on occasion in Spain (far more frequently than in the UK).


Initially you can use some basic monitoring methods to at least establish if the crack is getting worse e.g:-


Patch over a few sections of the crack with a band of non flexible filler or plaster. If it cracks through, there is some progressive movement going on. If it blows off, there may even be some closure occurring.


Draw a pencil line across the widest point of the crack and measure it’s width. Note the measurement and date next to the line e.g. ‘2mm 01/04/08’. Measure it again e.g. a couple of weeks/months later to see if there is a change, (alternatively measure between very wet and dry periods, which is commonly the most likely time of change). Such readings over at least 12 months, may confirm if a crack is historic, progressive or seasonal.


Draw a line across the furthest visible ends of the crack. Check back in the future to see if it has increased past the line.


Don’t take any risks if you have any suspicion that a crack’s progression could lead to structural failure, get it checked out immediately! Cordon off areas of risk if appropriate and if safe to do so, prop any suspect areas.



Often professional inspection may set aside your fears and confirm only a superficial cosmetic problem, (in some cases it saves lives), even superficial cracks can however be unsightly or even enough to put a potential buyer off a purchase, therefore recommendation of long term repair solutions by the Surveyor are normally welcome and help to save money on repeated covering up.


NB:- Information for advice purposes only. Proper legal procedures should be followed when carrying out all purchases and building works.  Information provided by Mark Paddon BSc Hons Building Surveying. MCIOB. Structural Surveys in the Valencia Community. WWW.SURVEYSSPAIN.COM T: 962807247 M: 653733066 . Free 17 page  property buyer’s guide and free initial free advice available by phone or via e-mail request to This email address is being protected from spambots. You need JavaScript enabled to view it.

Copyright Mark Paddon 2008


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