Firstly, apologies for the overly dramatic title but hopefully this will provide a useful example of the implications that a basement conversion can have on a property, where the work and guarantees which stand behind it are questionable.

In 2009 I took a call from a homeowner with a townhouse property in Manchester, they had just converted their basement / cellar to a habitable space, employing a local cellar conversion specialist to undertake the work.

There had been a few hiccups with work along the way, and while this was partly unrelated to the basement waterproofing, they advised that there were visible damp issues and as a result they had lost confidence in the waterproofing installation.

The homeowners had not yet paid in full and we were asked to inspect and provide advice in respect of what had been installed and works required to resolve the outstanding issues.

When I inspected it was fairly typical (at least at that point in time) in that cavity drainage waterproofing had been installed but there were no inspection/maintenance ports for the drainage channel system, and no evident battery back-up system for the sump pump – this meaning issue in the event of power cut – with omission probably motivated by cost. It was definitely a less than perfect spec.

In addition there were minimal areas of low level bubbling paint finishes, staining and efflorescent salts.  The general patterns indicated moisture penetration and certainly warranted further investigation.

I subsequently provided a written analysis and list of considerations which needed to be addressed. The main aspect that I stressed is that they should resolve the issues, pay the outstanding money and… get their guarantees.

I heard nothing further from the client and assumed that all was well.

Fast forward to 2015, and I’m asked to inspect a basement conversion with possible issues by a Manchester Building Surveying Practice and so off I go.  I meet the homeowners, walk downstairs and there I am, back in the basement in question!

I ask the homeowner if they bought it from my previous clients, which they did, and then I start looking around.  I can see that some of the issues (plumbing) have been resolved, but still no inspection ports or battery back-up, and while I could see evident redecoration I could still see the staining, there was now deterioration in timber floor finishes at the wall floor junction to the perimeter, high % moisture content readings from softwood timber skirting boards across a fairly wide area, also efflorescent salts causing paint to bubble and debond from the skim plaster it is applied to.  If anything conditions had worsened.

Efflorescent salt deposits form when water moving through the ground and/or building materials, dissolves salts contained within those materials.  These are held in solution, however when that moisture evaporates, i.e. changes from a liquid to a gas, the salts return to a solid state and form a crystalline deposit.

I don’t know what happened between the homeowner and the contractor but clearly the issues were not satisfactorily resolved.

I sent a copy of my original report to the Chartered Building Surveyor and discussed the considerations.  His first thought was obviously that of his own client and that if the property were purchased, what would it cost to correct, with the objective of ensuring no future issues, and addressing in a manner whereby we could provide guarantee?

With cavity drainage systems the key is in ensuring that the drainage element included within the floor construction functions as intended to collect and channel water to the means of removal, in this case a sump pump system.  We can only guarantee that which we treat and so as a minimum the work would have involved opening up, stripping out to expose the structural slab and most probably improving the detailing before replacing the waterproofing system (membrane/pump/channels) so that we protect the floor construction and low level wall areas.

This was not a small space and included a bathroom.  I estimated the costs at £25,000.00.

I can only assume that the prospective purchaser asked for a reduction or walked away, probably the latter.

This is the thing.. if any member of the public calls me asking about a basement conversion with issues and/or no/questionable guarantee cover, my advice would be to consider the implications very carefully, in that personally I would not seek to buy what are potentially expensive problems.

It makes more sense to purchase a property with a basement/cellar which has not yet been converted, than one which has been converted but has such issues.

This is because there may be a substantial cost in stripping out (in this case losing expensive timber floor finishes etc.), before you can even start to correct the waterproofing.

Note: I’m not publishing photos of this basement as that would obviously not be fair to the current owners – hence the redacted feature image!

You might think that such situations are a rarity, but I’ve just advised on a converted basement apartment in Didsbury, Manchester with issues where they got the installer back to remedy under guarantee then had me get me back out again because the repair was poor.

At the time of writing I’m working on a failed conversion in Altrincham where we are stripping out and renewing the cavity drainage waterproofing system to the floor construction, where they installed only one length of channel, ran that into a gravity drain and the system failed. The specialist installer can no longer be contacted so the homeowner is having to spend £9k with us to have most of the work undertaken again.

The full article can be found on:

Example flooded cellar due to tanking failure

What can happen when you don't get it right - tanking failure.

When dealing with waterproofing and basement design, there are typically options in respect of the methods or 'types' of system that could be selected, with the objective of creating a dry basement which stays dry in the long term.

Different systems provide different levels of protection/risk and so what we are always interested in, is the lowest risk system.  This is because we provide guarantees on the systems that we install, and so would not survive in business for very long if we employed risky systems which required us to go back, and back and back, and believe me this happens to others, which perhaps explain why there are so many basement conversion/basement design companies which start up and then seemingly dissappear year after year (another blog post in itself)! 

So, we have to justify and explain our basement design choices to the clients and professionals involved in a given scheme, which we do time and time again, however it's fantastic when a client just gets it, as experienced on an inspection yesterday.  

This chap had little in the way of construction knowledge, but securely grasped the principles explained to him in respect of why we do what we do.  He will get a dry basement. 

Although this should always be the case where a detailed explanation is given, we in some cases have to deal with preconceived notions of what 'waterproofing' is right for a given basement scheme, and it can be that the more an individual knows about construction, the more they believe they know about basement waterproofing, and the less willing they are to accept alternative ideas, even when this means a much more detailed and rationalised basement design process, versus simply choosing a product and shoehorning it into a given site and structure. 

The assumption that basement waterproofing design is a simple matter results in what must be millions of pounds of headache and remedial work each year, which the new BS8102 design guide (the UK waterproofing bible) deals with by repeatedly advising that waterproofing specialists (like Trace) should be involved in a project at the earliest stages.  

Looking back to my younger years, whenever I believed I knew it all, it wasn't typically long until I was shown that I did not.  The lesson is, that an open mind is a vehicle for learning, and that where basement waterproofing is concerned, you do not want to learn this the hard way. 

...and furthermore, listen to the advice provided by those that will have to honour the guarantee, rather than those who simply profit whether it works or not (another blog post to write!).  Also see: 

Thanks for reading.

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