Basement & Cellar Conversion

At Trace we are passionate about the creation of extraordinary living space, from even the most dankest darkest basement and cellar spaces.

Our designers work attentively with clients to create intuitive space designed for living, with meticulous consideration of quality, fit & finish, delivered in a professional manner.

Below we include examples of recent basement and cellar conversion projects which included a variety of work from underpinning to achieve greater height, and the excavation/formation  of an external stairwell & door.

While photographs tell their own story, if you have questions or wish to discuss such a project, feel free to contact us and speak with our qualified basement conversion designers.

This wall (above) was removed to form the open area including the table football, visible opposite.

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Below we include further advice & considerations appropriate to basement and cellar conversions:

Basement & cellar conversion is the process of taking basic basement and cellar spaces and improving the environment via the inclusion of a waterproofing system in association with heating & ventilation, so that the basement or cellar can then be employed as a habitable space.

Trace manage basement conversion in Manchester (and further afield) from design through to completion and have done so sucessfully for over twelve years. If you are interested in discussing your requirements and recieving professional advice & service, please contact us.

Our mantra is that educated customers make the right decisions, and so provide this website as an information resource available to those who are considering having this work undertaken:

We also include a degree of general advice below, which will be of assistance if you are considering basement conversion in Manchester or cellar conversion anywhere else for that matter.

Example basement conversion in Manchester prior to works:


Basement conversion in Manchester post completion:


Waterproofing, is it necessary?

The waterproofing system is critical in basement conversion and cellar conversion projects, in that it protects the internal fixtures, fittings and finishes (plasterboard, carpets etc.) against damp, wet or potentially damp substrates (walls and floors) so that the materials installed do not deteriorate and clients can enjoy warm dry habitable space, which stays dry in the long term.

What if the cellar is dry?!

Well that may be so, but the basement conversion process (as stated above) inevitably involves the introduction of materials and belongings which are sensitive to moisture, this including water vapour.

Because basements and cellars have earth which bears against the walls; and this earth has a propensity to hold moisture as a result of rainfall, even in a ‘dry’ space the walls (and floors) are likely to contain a degree of dampness.  If you take those walls that are allowed to breathe at present, and then enclose them in behind plasterboard linings, it is likely that deterioration will occur in time and that this will require spending more putting it right, than it would have cost to do it right the first time.

showimageThis example (photo right) shows a basement conversion in Manchester, where minimal damage is occurring, but in a finished space this is just not acceptable.

A great deal of the remedial work (fixing failed systems) that we undertake is to address minimal damage of this nature.  While this may seem slight, if you want to ensure that such problems are not encountered again, it can involve substantial works.  Hence, due consideration should be given to the provision of reliable waterproofing.

Furthermore, where investment is put into a space and the objective is to protect that investment, one should always design for future risks, in that what once was dry may not always stay that way.

showimageThis (photo right) is an example of a basement conversion in Manchester, North West, purchased by a young couple , where conversion had been undertaken prior to their purchase.  For approximately two years the space was dry and useable, however Christmas came and brought rainfall with it.  Groundwater pressure came to bear, but there was no waterproofing system included to deal with this, and as a result the space (a home office) flooded.  The floor finish is an Italian white rubber floor tile, stained by the water penetration.

showimagePhoto right shows water pouring into the spacethrough a small hole drilled into the floor construction by the homeowner.  A small pump was then used to pump out the water.

showimageDamaged wall finishes:

We subsequently stripped out fully, installed a waterproofing system and then reinstated fixtures, fittings and finishes.  While the problem is now solved, it serves as an example that ground conditions may change in time.  While this is certainly an extreme example, a small amount of dampness is enough to cause issues in a finished space.

Building Regulations Applications, why is it necessary?
When a basement or cellar is converted from a cold damp space into a living area, this represents a ‘change of use’, from non-habitable to habitable space.  Like new houses, ‘new’ habitable space must comply with the building regulations (which are statutory/UK law), which for example means the inclusion of insulation within the walls and floors (ensuring that the space is efficient to heat), and consideration of other aspects such as means of escape in the event of a fire.

Subject to the appropriate considerations being designed and constructed, the local authority will issue a completion certificate, which then recognises the use of the space as a habitable area.

The main benefit of going through this process when undertaking basement conversion or cellar conversion, is that you get maximum value out of the space (a better return on your investment), because when the property is sold, the basement can be sold as a habitable part of the property.

If you do not obtain a completion certificate, when you come to sell the property and fill out the ‘sellers property information form’ concerning any such works that have been undertaken, you would have to declare that there is no completion certificate, and may be offered less for the property as a result, or you have to apply for the approval retrospectively and put right any work that does not comply to obtain the certificate.

Despite the benefits of going through this process, it is only natural that some homeowners question the worth, and perhaps do not see the full benefit.  We would make the following comments:

Trace have developed standardised specifications which can be employed and approved in 95% of the basement & cellar conversions that we undertake, or tailored wherever necessary, making the process simple and painless, (simply put, we are very experienced in this).

We have gained further standardisation and acceptance by using a system which holds a ‘Local Authority National Type Approval Certificate’ (#340-12-7128), and by partnering with our local authority building control department (High Peak) under the LABC Partner Authority Scheme (PAS).  This means that when we (or partner consultants) submit an application for basement conversion in Manchester or anywhere in the country, it can be dealt with by our local partners who are familiar with our specifications.

When going through this process, we always submit a ‘full plans application’, which means that we produce drawings illustrating exactly what we are going to do, which are submitted and approved by Building Control before we start.

The alternative to this is that a ‘building notice’ is used.  A building notice does not require any drawings to be submitted, you can fill in the form, submit this and start within 48 hours however there is a condition, in that if any work is undertaken which does not comply (works are physically inspected), it will need to be corrected which may involve stripping out and correcting works already installed.

Submission of a building notice form is no cheaper than submitting full plans, but carries additional risk.
By submitting full plans applications before commencement, we can avoid such risks and this has a variety of benefits:

• We provide accurate costs because works are agreed up-front.
• Fewer queries (and a quicker service as a result).
• Less variation & no works to correct (again providing a quicker service and potentially lessened costs versus corrective work).

Based on the above, you might question why anyone would use building notices, but we know from providing talks to Local Authority Building Control depts. on basement conversion in Manchester & the North West, that for example, in one Manchester borough, 95% of basement & cellar conversion is being undertaken by non-specialists predominantly using building notices in place of full plans applications.

Why is this?  Well, these are some of the possible implications of using a building notice:

• Less work – you don’t have to produce the drawings for submission.
• Potential for lesser scrutiny of the design – Building Inspectors advised me that often, contractors encourage visits by the Building Inspectors when the waterproofing is concealed behind dry linings (plasterboard).
• More scope to go for extra costs.  If ‘extras’ come from the demands of the Building Inspector (note that the Building Regulations are statutory i.e. UK law), then one can devolve responsibility for those extra costs to the demands of the building inspector.  The homeowner then has no choice but to pay up or argue it out with the contractor.

While building notices certainly have their place, and can be useful where you can be certain that works will comply, they can also have their risks.

If you the consumer, have a basement conversion undertaken by others, my advice would be to ask the question as to whether full plans or a notice is being employed.  If a notice is being used, ask who will accept responsibility if the Building Inspector makes demands not originally priced for.

In such a scenario, the builder/specialist would be viewed as the ‘expert’ therefore owing a duty of care to the client, and from this perspective they should either forewarn the client of such foreseeable risks (i.e. a fixed price quotation may alter), or accept them (a fixed price quotation remains fixed – but make sure you read the terms & conditions).

I found one example of this online on a web forum associated with building works.

The post read as follows:

“The building controller has suggested a full set of stairs at the front of the property from ground level to the window installed in the cellar. This really isn’t possible as our house is a mid terraced victorian property which has a small front garden which 1) if runs along side the house would weaken foundations and the top of the stairs would be close to the fence of our neighbours and be next to there window and our gas meter 2) if runs out from the house would finish a matter of feet away from the edge of our property and public footpath.

When the conversion company started the work, we submited the appropriate forms to the council detailing the work and the inspector came out, checked the work we’d be doing and never mentioned anything about the chute even though it was discussed. its only become a problem now”.

I’m currently trying to determine what the outcome of this was, but it serves as an example of what can occur.

We have our own preferences and feel that what we do provides the best result for Trace, and our clients.  If others choose the alternative then that is their choice, but at least if you are aware of this you can check and hopefully protect against such scenario’s.

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Waterproofing & Quality – what to consider.
Trace were the first company to specialise in basement conversion in Manchester & the North West, being the first to place an advert in the Yellow Pages for basement conversion in Manchester, under the ‘damp proofing’ section.  Today ‘basement & cellar conversion’ is its own section.

This market has expanded exponentially in recent years, and these days it is not uncommon to see ‘basement conversion’, on the side of a wide variety of contractors vans.  With a greater number of contractors comes price competition, which is great for the consumer, as long as low price is not achieved by providing low quality.

This is not to denegrate our competitors, but where there are many firms competing for little work, as experienced during a recession, we have become aware of firms installing limited specifications which would cause us concern.

We seek to raise standards within the industry so that clients receive greater protection, and we compete on a level playing field.  Aside from our involvement within the industry, including serving as examiners on the CSSW (certificate in surveying for structural waterproofing), we are active in various trade associations including PCA & TBIC.

Some examples:
A typical drained protection waterproofing installation involves the installation of a purpose designed drainage channel around the perimeter of a basement, which collects water and diverts this to the drainage point, which may be a sump pump system or low ground externally if the property is built into a hillside.

These drainage channels are installed at the point in which most water penetrates, the idea being that water drains directly into the channels and then directly to the drainage point.  This is good design, because any silt/sediment/salts is caught within the channels, and one can include inspection/access ports so that the channels can be maintained and cleaned out, meaning that the system will continue to function and protect in the long term.

What we may see when asked to inspect systems installed by others, is that inspection ports are not included.  When speaking to the aforementioned borough of Manchester Building Control dept. in 2009 about the necessity to construct maintainable systems (which is covered in the British Standard 8102 for structural waterproofing), they actually advised that in all of their inspections they had not ever seen a single inspection port included.  This included site inspections where waterproofing manufacturer reps had been present and talked them through the installations!

showimageTaking this on a step further, it is theoretically possible to construct drainage based waterproofing systems without including any channels whatsoever, instead wholly relying on the cavity formed by the dimple in a cavity drainage membrane.

Such a design is cost effective to install, because the membrane is not that expensive (labour is the greater cost) and you can omit cuting or forming channel chases which can be labour intensive, nor do you have to buy the drainage channels, or fit ports within them.

The trade-off is that you cannot readily clean out beneath the membrane as you can within the drainage channels, and if the membrane clogs in time it will cause disruptive and expensive problems.  So, while we would love to compete on low price/quality and win more work on that basis, this would in our opinion be short sighted, in that sooner or later we would inevitably have claims on our guarantees.

This is an example of a such a specification which came back to bite.

1The waterproofing design for this property included an 8mm cavity drainage membrane laid direct over a new concrete slab.  A sump pump was included at one end of the basement, so in essence any penetrating water would run beneath the membrane until it reached the sump, where it would then spill over the edge and be pumped out of the property.

Approximately two years after completion, water started to come up through the floor construction, and the homeowner asked Trace to investigate.

2We attended site and could see the cavity membrane which had been installed.  We then promptly identified that there were no drainage channels and therefore no access ports and no means by which the system could be maintained.

Water moving over or through new concrete can leach free lime (calcium carbonate), unless the concrete is suitably treated.  This design, which allowed water to move across the full breadth of the floor slab, allowed so much lime to be leached that it ultimately clogged up the drainage space beneath the membrane, this causing system failure.

3If channels were included at the perimeter, firstly this would have stopped water from flowing fully across the floor slab (a large surface area = more free lime), but the system could also have been constructed to allow maintenance, meaning that it could be cleaned out.

The deficiency in the design and the extent of clogging was such that the only solution was to fully remove the floor screed and the membrane beneath, then cleaning away the lime, then retrofitting drainage channels & ports and reinstating membrane and screed or timber flooring over.

4Although the design clearly did not comply with the requirements of British Standard 8102 to construct maintainable systems, the installing contractor (no longer in business but contactable) argued that the design was approved and that they were not liable.

Some membrane manufacturers do state that systems can be formed using membranes only, but in certain situations, this not being one of them.  In any case it was a poor specification which should not have been installed, and furthermore there was no battery back-up on the sump pump system.

5Not including battery back-up protection (protects in the event of a power cut) is another method by which cost is kept down at the expense of risk.  We have seen flooding in basements as a result of this – you can read more about this on our sump pump systems page.

So there you have it, a few things to consider if you looking for basement conversion in Manchester, or anywhere else for that matter.  If you do wish to discuss requirements in respect of basement conversion in Manchester, or cellar conversion, please get in touch. We work in Manchester, the North West and further afield.

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