Structurally Unsound Composite Floor Joists

Floor Fails to Take the Load in Bovis New Build

 

Typical composite I Beam

Typical composite I Beam

We carried out an inspection of a Bovis new build last week that was less than 2 years old and in buildings of this age you don’t expect to find structurally unsound composite floor joists in the floor but that is precisely what we did find.

Visual Defects

We noted a number of defects to the first floor all centred on the landing area between three bedroom access doors and the airing cupboard.

We noted a large run out to the base of a bedroom door but checking the door showed it to be square, whereas the floor to the landing area was sloped significantly.

Significant slope to floor

Significant slope to floor

Moreover, we noted large gaps to the base of the bedroom door frames, which were so large that we could see where the nails in the sole plate had pulled from the floor as the floor had sank.

We then found that the dividing wall between the bedroom and airing cupboard could actually be rocked from side to side, and of course this movement explained why a number of cracks had opened up to skirting boards and door architraves.

 

Floor defects point to simple conclusion

We’ve inspected properties on this site before so we are intimately familiar with the construction and poor build quality so we know that the floors are constructed using composite I beams, which are then overlaid with tongue and grooved chipboard.

Floor separating from stud wall

Floor separating from stud wall

 

 

 

 

 

 

 

 

 

 

 

 

Insecure stud walling

Insecure stud walling

Failure of Composite Floor Joists

In this particular case  the range of defects led to one very obvious and significant conclusion, the floor was failing under the weight of the Megaflo hot water cylinder in the airing cupboard. The cylinder was not sat on a plinth and we are of the opinion that the floor was not strengthened in any way to take the significant  weight of this live load, which could be in the region of 350Kg’s.

 

As expected we also noted that the kitchen ceiling below was showing evidence of bowing under the live load and we have to wonder how many more properties on this new development will suffer from the same problem?

Floor sinking under the load of the Megaflo cylinder

Floor sinking under the load of the Megaflo cylinder

 

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The worst brickwork we’ve ever seen?: A new contender.

Declining Standards in New Build Highlighted by the worst brickwork we’ve ever seen.

Norwich New Build

Norwich New Build

Back in July we were called to carry out a snagging inspection to a David Wilson Homes site in Norwich, which had the worst brickwork we’ve ever seen. Our clients had signed up to buy a new build ‘off plan’ but started to have grave concerns relating to the quality of their potential new home as they watched the build progress. Our initial discussion related to the fact that the brickwork colour was mismatched and that the developer had employed someone to tint the bricks to match; when I arrived on site to carry out the snagging inspection the specialist was at work  painting individual bricks with a pot of red tint solution and a paint brush, a quite laborious task as you can imagine.

We’d agreed to inspect before the build was complete because our discussions with the client, and indeed pictures sent to us, gave enough cause for concern that this was necessary.  The following image slider will give you a feel for the quality of the work and the sheer volume of defects we encountered. Please view the slider on full screen to fully appreciate the illustrated defects.

Would you have bought this house?

Norwich new build
OLYMPUS DIGITAL CAMERA
Bridged polyethylene DPC
Oversailing brickwork
Cracked bricks
Failed mortar joint
Poor pointing
Cracked bed joint
Poor standard of pointing
Protruding perp weeps
Poor setting out
Perps out of alignment
Overly wide mortar perp
Inconsistent mortar joints
walls out of plumb
Smeared pointing work
OLYMPUS DIGITAL CAMERA

Significant Defects

As you can see the defects were significant and we commented in our report that we found it difficult to believe that this brickwork was completed by a fully qualified brick layer. Of particular concern was the incredibly poor setting out, failed mortar bed joints, inconsistency in width and depth of mortar joints and last but not least, walls that were significantly out of plumb, well beyond the 8mm maximum allowable NHBC tolerance. As often happens in these cases it was relayed back to us from our client that the developer didn’t agree with our report and that a site manager of 20 years experience knows more than us and his view is that the brickwork was perfectly acceptable. I thought it may be useful to balance the Chartered professionals view with a second opinion  from a master bricklayer and obtained the following commentary from an acquaintance who is also a master bricklayer…

The master bricklayers view

“My name is Bill XXXXXX and I have been a brick layer for the last 30 years.  I have City and Guilds  NVQ level 3 in brick laying  and NVQ level  6  in site management. I’ve been asked by Joe Malone  for my opinion  about the workmanship of Plot XXX in Norwich.

There seems to be wide and inconsistent perpendiculars and significant variation in bed joints.

The pointing is of a very low and poor standard i.e. holes and not perps not ’top and tailed correctly’

Weep holes are protruding out of the brick work and should be flush.

Also bricks have been laid upside down allowing moisture to catch on the face leading to premature failure through ‘spalling’ aka frost damage.

The walls are significantly out of plumb. Variation in plumb should on good brick work be a maximum of 4l mm out of plumb one way or another. Brick courses seem to wander. Chipped bricks have been used rather than discarded. The Brick work is over sailing be 10mm in places below the DPC

There are large gaps around some windows which implies poor setting out.

Some bricks are cracked and should have been discarded. Two failed bed joints are apparent.

The brick work has not been washed or cleaned down.

The mortar colour varies implying it has not been ‘gauged’ and makes the building look patchy.

The damp course is protruding through the mortar.

Back straps for the garage have been missed. Roof ridge work is poorly finished and there appears to be no mechanical fixings

The brick work does not appear to be ‘fair faced’

In all a very poor standard of work has been delivered with a significant amount of snagging already required.

On a site managed by our company this work would be condemned and the brick layers replaced or forced to do the work again to our own companies’ standard.”

The only point on which we don’t agree with on this second opinion is with regard to the DPC being pointed over. DPC’s should not be pointed over, they should be exposed and clearly visible and if they are not then they are bridged.

The worst Brickwork

Our clients reached something of stalemate with their developer, because they were insisting that sections of the building were taken down and rebuilt, whilst the developer was offering minor remedial works that fell well short of dealing with the significant defects in this build. Their complaint was ultimately elevated to the managing director of David Wilson Homes and our client eventually informed us of the following outcome, “We have decided not to proceed with the purchase of the house. I think we always knew this was the outcome deep down. I have received a reply letter from the MD of David Wilson East division offering to rescind the contract and contribute towards ‘reasonable’ conveyance costs.”

When we last spoke our clients were looking to purchase an old traditional property and we completely understand why, moreover, we believe that they made absolutely the right decision to withdraw from this contract. A brave and sensible decision, especially when you consider that many clients purchase with their heart rather than their head.

 

 

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Sealing the Deal: Building Sealants. A Useful Guide (Part 1)

Background of Building Sealants

We commonly find significant problems with building sealants, problems range from:

  • Unsealed critical junction details
  • Poorly applied sealant
  • Poorly re-applied sealants
  • Incorrect choice of sealant
  • Premature sealant failure
A vast range of sealants are available but how do you choose the right product?

A vast range of sealants are available but how do you choose the right product?

Sealants are possibly one of the most under-appreciated products in the construction industry and yet they often provide the critical technical detailing that will determine the long-term durability of you project. They can protect a multi-million pound external wall insulation project from failing prematurely, provide essential fire protection detailing or just be used as simple caulking to aid in providing a high quality internal decorative finish.

However, there are such a wide range of products available how do you choose the right product for your project? What are the dangers in choosing the wrong product, what supplementary factors also need consideration when choosing sealants and how should sealants be applied?

Sealant technology has progressed significantly over the last 30 years and we now have intumescent sealants available for sealing service penetrations in fire walls, lead sealants used as an alternative to mortaring lead flashings and even bacteriostatic cold room sealants to be used in areas where contact with food is possible.

Historically, ‘caulking’ was used to make heavy wooden ships watertight by soaking hemp in pine tar (Oakum) and driving it into the joints of the ship. The term caulking, is still used loosely to describe the sealing of building joints but more often it refers to internal decorative caulking, whereas we generally refer to ‘sealant’ as being required for external building applications. To my mind there have been some worrying developments in sealant marketing, rather than technology, in particular the marketing of lead sealants as a direct replacement for mortar and we are already encountering numerous cases of premature flashing failure due to premature sealant failure; particularly since the lead pegging is often omitted when sealant is chosen over mortar.  To  my mind lead flashing sealants should never be used for anything other than a temporary fix or at best you should accept that flashing durability will be significantly reduced when compared to mortar.

Causes of Failure

There are two types of failure found in sealants, adhesive and cohesive failure.

Screen Shot 2016-06-12 at 08.13.37

Adhesive failure on left and cohesive failure on right.

 

 

 

 

 

 

 

 

 

 

Adhesive Failure

More commonly seen adhesive failure of lead mastic sealant on new construction

More commonly seen adhesive failure of lead mastic sealant on new construction

Adhesive failure is recognised as a failure occurring at the joint interface with the building substrate and usually occurs for one of the following reasons:

  • Poor preparation of the joint, perhaps primer should have been applied.
  • Dusty, dirty or contaminated joint interfaces.
  • Sealant applied to damp surfaces
  • Lack of joint backing
  • Lack of tooling during application
  • Incorrectly specified sealant (Expansion & contraction characteristics not suited to application. Failure to choose low modulus sealants for PVCu windows & doors is a common problem)
  • Thermal movement occurring in the building substrate before the sealant has set
  • Old sealant not removed prior to reapplication.
  • Incompatible coatings applied over sealant. Some paints may chemically react.
  • Inadequate depth of sealant
  • Overly wide joints

Cohesive Failure

Less common cohesive failure

Less common cohesive failure

Cohesive failure is relatively uncommon when compared to adhesive failure but is recognised as the splitting of the sealant material rather than failure of the bond with the substrate; it usually occurs for the following reasons:

  • The thermal movement in the building joint exceeds the sealants elastic limit.
  • Lack of joint backing causes inability for movement to be spread across the whole sealant joint.
  • Inconsistent depth of sealant.
  • Thermal movement occurring in the building substrate before the sealant has set
  • Movement joint too small due to poor design and inadequate allowance for thermal movement in the building envelope.
  • Cheap, poor quality sealants.
  • Poor mixing of two part sealants.
  • Air or moisture entrapment results in expansion of air or vapour that can cause the sealant to bubble or fracture.
  • Age related loss of properties

Sealant Omission

It is incredible to think that constructors would complete a project worth hundreds of thousands or even millions of pounds then put that project at risk by omitting to use sealant at critical junction details but we commonly see precisely this problem, particularly on external wall insulation projects. Then there is the common problem we see of timber windows being sealed with hard inflexible mortar fillets, which quickly crack and fail after application and more recently the trend of fixing in windows and doors using nothing more than expanding polystyrene foam as both a fixative and a sealant, when in fact in can not adequately serve either role.

Newly applied OPC mortar fillets to window frames cracked within days of being applied. Note complete absence of sealant.

Newly applied OPC mortar fillets to window frames cracked within days of being applied. Note complete absence of sealant.

Window fixed and sealed using expanding polystyrene foam.

Window fixed and sealed using expanding polystyrene foam.

 

 

 

 

 

 

 

 

 

 

 

Tools & Workmanship

Poor application of sealant is a common problem we find, even on new build sites were you would almost definitely expect a high quality finish and of course this is often more than an aesthetic problem. Untidy or un-tooled sealant often lacks the durability of a well finished joint. Contractors tend to approach the application of sealant in one of three ways:

  1. They employ a site finisher who applies the sealant and finishing touches to a project.
  2. They may outsource sealant to a professional sealant company
  3. They give it little thought due to programme pressures and it gets forgotten or applied, often grudgingly, by any tradesman in the area who doesn’t really see it as his job.

The latter approach tends to result in sealant that looks like this…

Poorly applied and unsightly silicone sealant

Poorly applied and unsightly silicone sealant

 

Various cheap plastic tools exist to provide a high quality surface finish to sealants so why not use them?

Various cheap plastic tools exist to provide a high quality surface finish to sealants so why not use them?

It costs a couple of pounds to buy a plastic tool that will give a high quality finish to the surface of sealant, facilitate better edge adhesion and properly tool the material into the full depth of the joint but sealant is comply untooled or simply finished by running a thumb or finger along the joint. Given the cost and obvious benefit in using these tools it’s hard to see why they are not more commonly used.

Width & Depth of Joints

There is a minimum depth of sealant that should be applied and generally speaking this is around 5mm but can be up to 15mm for some sealants and you should check individual manufacturers instructions. A more common problem we see is where sealants have been used in gaps that exceed their maximum permissible joint width. We’ll include a joint width guide in the table published in part 2 but applying sealant to an overly large gap can result in almost immediate adhesive failure of the sealant on curing, as in this case.

Large gap between window frame and masonry is too wide for the choice of sealant here.

Large gap between window frame and masonry is too wide for the choice of sealant here.

 

 

 

 

 

 

 

 

 

 

 

Which sealant should you choose?

We’ve put together a handy guide which will be published in part 2 to help you choose the right sealant  for the particular job under consideration.

Removing Old Sealant

When re-applying sealant it is critical that old or existing sealant is removed back to bare substrate. Applying fresh sealant over the top will simply lead to premature failure. It can be challenging to cut away or peel off old sealant but there are various tools and products on the market that will make this job easier. There are special tools to help cut away sealant and gels that can be applied to to break down acrylic and silicone sealants.

Sealant removal gel

Sealant removal gel

Special sealant cutting and profiling tool

Special sealant cutting and profiling tool

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EXTERNAL WALL INSULATION: The Defects are Often Built in. Part 2

The First Visual Signs of Premature Failure Explained

Underlying Rockwool Insulation Slabs Now Visible

Underlying Rockwool Insulation Slabs Now Visible

Some time back we blogged about a Midlands high rise EWI scheme that we’d monitored and noted that defects were being built in. Interestingly we have now noted very obvious visual signs of premature wall cladding failure. In fact we recently investigated a failed EWI scheme that exhibited a number of visual problems that were also noted on this scheme. When you consider that it generally costs circa £1m to install EWI to a high rise block then system failures become extremely expensive to remedy. In this particular case I drove past the building today and immediately noted early visual signs of system failure, in particular, what we call ‘thin coat failure.’ The white finished render should be ‘in plane’ and present a smooth finish across the whole facade but in this particular case you can now see that the underlying Rockwool insulation slabs in the Alsecco system are clearly visible; so what causes this and what are the implications?

Pillowing & Mattressing

We have previously written about the effects of pillowing and mattressing but this is something generally seen in Phenolic insulation boards, it isn’t a problem you see in Rockwool slabs.  Please read http://buildingdefectanalysis.co.uk/solid-wall-insulation-ewi/a-case-of-pillowing-or-mattressing/ for more information.

Technical Issues

Since we had initially commented that insufficient hammer fixings were being installed to the Rockwool slabs then we also believe that there is risk of structural failure at the interface between the Rockwool slab and the underlying substrate. However, experience tells us that the visual evidence suggest something far simpler… The render base coat has probably been applied far too thinly.  It is a problem that we are commonly seeing and we’re unsure if this is a result of the construction bean counters short ordering materials or whether it is simply down to poor site quality management?  The problem with overly thin render coats stretches well beyond the obvious aesthetic problem and raises two key technical issues.

  1. An overly thin render coat does not have the same impact resistance.
  2. An overly thin render coat is more permeable and hence far more susceptible to penetrating damp and subsequent saturation of the underlying insulation.
Another elevation with underlying Rockwool slab insulation clearly visible.

Another elevation with underlying Rockwool slab insulation clearly visible.

Thin Coat Failure

So we believe that this system is suffering from thin coat failure and has failed prematurely on both aesthetic and technical grounds and we predict significant technical problems in the near future. The only subjective discussion is with regard to the degree of failure exhibited.

You may wonder why these thin render coat failures are not immediately obvious on works completion and we think that is down to simple curing and shrinkage of the render, which can occur over a number of months; this project was only completed in October 2015 but visual system failures had to be evident months before we observed them. As the render coat shrinks back, it thins to reveal the underlying insulation boards, usually first noticeable when sunlight hits the elevation concerned.

Solution to Failure?

So, is there a remedy for this? If caught early enough before water penetrates and saturates the insulation, is there a quick fix? Sadly no. The problem is that whilst it may seem reasonable to offer additional coats to increase the render thickness, this  system would no longer have BBA approval. The reason for this is simple… You would be applying further base coat over an existing topcoat but the system was never tested with base coat applied over topcoat and therefore would no longer be BBA approved. We have written correspondence from the BBA stating precisely that fact.

Poor installation of Rockwool slabs.

Poor installation of Rockwool slabs.

It is easier to contextualise this system failure when comparing the underlying defects noted as the system was being installed and here we can see the poorly installed rectangular insulation slabs that are now showing through the render coat.

In our opinion both Rockwool slabs and EPS boards offer greater flexibility and potential for at least partial recovery of the EWI system but even retaining the insulation needs careful consideration based on a detailed investigation and recovery of site evidence.

 

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Building Defects: A legal perspective

Guest Blog Introduction and Biography

In March of this year both myself and Sarah Fox attended the RICS East Midlands CPD conference as guest speakers. I’d not met Sarah at this point and was lucky enough to attend her talk on letters of intent. Quite simply it was possibly the best talk on contract law that I’d ever attended and I was so impressed with Sarah’s knowledge of contract law that I asked if she’d write a guest blog.

Sarah Fox is a construction contracts strategist and author of a series of 500-word construction contracts. She wants the industry to adopt contracts that they can read, understand and use. She uses coaching, talks and workshops to help professionals to write simple contracts and understand complex ones. Her keynote is “Never sign on the dotted line” and you can find out more at http://www.500words.co.uk

Patent and Latent Defects

“Defects will occur in buildings. It is one of the great certainties in construction, the equivalent of death and taxes in life more generally” [1]

Borescope used to locate a latent defect.

Borescope used to locate a latent defect.

Generally a defect is “anything which renders the [works] unfit for the use for which it is intended, when used in a reasonable way and with reasonable care.” [2]

There are two types of defect: patent and latent. Patent defects are defects that are visible or capable of being discovered (observed and observable). Latent defects are not reasonably discoverable and often come to come to light after completion and even after the defects period.

Any client needs to ensure that the works meet the required contractual standards for goods, design and workmanship. This can be done in a number of phases:

During Construction

The contract administrator must identify visible defects and exercise her powers before completion and ensures that issues relating to quality and defects do not wait until the defects period. Depending on the terms of the building contract, the contract administrator may have:

  • the power to issue instructions to require the removal from site of work or materials not in accordance with the contract (JCT 2011 DB clause 3.13.1)[3] or other instructions as appropriate (JCT clause 3.14);
  • the power to require the contractor to open up or test various elements of the works (JCT clause 3.12);
  • a duty not to include in interim certificates the value of works not in accordance with the contract (JCT clause 4.14.1.1);
  • a right for the employer to terminate the contractor’s employment for failure to rectify defects as instructed, provided the works are materially affected (JCT clause 8.4.3);
  • the duty to confirm whether the works are completed to her satisfaction (MF/1 rev 5 clause 13.2);
  • the ability to confirm the performance of the works through testing before and after completion (MF/1 clauses 23, 28 and 35).

Obvious or ‘patent’ defects should prevent the issue of the certificate of completion. Accordingly, the date of completion, all work should conform to the requirements of the contract.

During Defects Period

Patent defect found on new development site.

Patent defect found on new development site.

Building contracts ‘encourage’ the contractor to return to the project and make defects right by allowing the employer to withhold some of the money due to the contractor until the end of the defects period, either a stage payment or retention. In Pearce & High v Baxter, the court said (with some reservations) that the JCT Minor Works wording “can be regarded as giving the contractor a right to make good defects at his own expense, and a licence to enter the property for that purpose.” [4]

After Defects Period

Once the defects period has come to an end, the client can bring a claim for breach of contract for any defects which become patent during the limitation period. The client’s claim is for damages to put it in the position it would have been in if the contractor had carried out the contract properly.

The difficulty is measuring what is an appropriate amount of damages.

 

Referencing

[1]           Article by Harrison Consult quoting Professor Anthony Lavers.

[2]                 Yarmouth v France (1887) 19 QBD 647. See also Tate v Latham [1987] 1 QB 502 where a defect meant the absence of an item essential to complete the works – even if the works were operable without the item.

[3]           There is no power for the contract administrator to instruct when these defects must be rectified as it is for the contractor to plan and perform the works however it chooses. All references in this blog are to JCT 2011 DB unless otherwise noted.

[4]                 [1999] CLC 749 at 751.

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