Basement Conversion Harrogate – Playroom

Danford Brewer & Ives undertook a basement conversion on a property in Harrogate during the spring of 2018.

It is a terrace house, constructed of stone, with a slate roof, brick chimney, UPVC guttering, wooden windows and stone flag floors.

The owner’s intention was to convert the basement into a playroom for his children.  They also wanted a utility room, a toilet and two storage areas/cupboards, each separated by internal walls from a landing that leads to a new staircase.

The process was as follows:

  1. Damp Survey

We first needed to ascertain what level of damp the existing basement had. The survey was restricted to the basement and our readings (taken with the aid of an electrical conductivity-type moisture meter known as a Protimeter) revealed evidence of rising and penetrating damp to all areas, as well as water ingress.

Two major causes of the damp were the high ground levels and structural abutments, so we recommended that either the external levels were reduced or an internal barrier, incorporating a waterproofing agent or membrane, was applied and fixed to those areas – at least up to the level of the newly installed damp-proof course.

(NB We did not undertake a structural survey and always recommend that any worries/queries regarding such issues should be resolved using a suitably qualified person.)

  1. Structural and basement waterproofing

All work was undertaken in accordance with British Standards Document BS 8102:2009, the code of practice for the protection of below-ground structures against water.

It specifies a level of protection (grading from 1-3) based upon the end use of the conversion. In this instance, since it is being used as habitable accommodation, the required grade was 3.
One assumption BS 8102:2009 makes is that ingress will occur during the conversion’s lifetime – caused, for example, by a change in the water table, drains becoming blocked or heavy rainfall causing localised saturation.

After careful consideration of various methods of controlling persistent water entry, therefore, we recommended installing our cavity drain system to all areas indicated on the plan.

  1. Drainage

The cavity drain system’s effectiveness is based upon discharging free water, before pressure builds behind the system.

For this to be possible, an effective and fully maintainable drainage system was installed.

  1. Preparatory Work

The existing ceilings were stripped, with plumbing and electrics relocated in the ceiling.

Some timber repairs were required in the utility area. Where there were signs of deterioration, the timbers were cut back and replaced by either steel support brackets or resin ties.
The existing opening into the floor void was increased to approx. 2.4m wide by installing a new concrete lintel (that was subject to a structural engineer’s approval). An area, approx 1200mm back into the void, was then lined with a membrane and framed out to form a new storage area.

The existing single skin brick wall in the utility area was removed (no structural replacement was required) and the stone staircase was broken out and also removed.
We lifted the existing stone flagged flooring, which was kept for the client, and the floor was excavated by a depth of approx. 100mm to allow for the build up of the membrane and floor finishes.

  1. Waterproofing

A sacrificial screed was poured incorporating a 100mm x 75mm perimeter rebate. Once the floor was cured and prior to membranes being installed, the concrete was treated with an anti-lime coating to stop the build-up of free lime within the cement and prevent the drainage from blocking.

The walls were lined with an 8mm studded Cavity Drain Membrane. This was installed to at least the height of damp course level.
A perimeter drainage channel was installed, complete with servicing flushing points. The drainage falls and collects within the sump chamber and any water build-up is discharged via the twin pumps located within. Each pump has its own independent fused spur supply.

Once the drainage and pumps were installed, we flood-tested the system.
The floors then received a 20mm CDM which was sealed to the wall membrane as required. The system was then flood-tested again.

  1. Fit out

To be compliant with current building regulations, and as the basement is a habitable space, insulation was required (our specification was subject to Building Control approval).
We laid a minimum 50mm close cell insulation board on top of the floor membrane and covered it with a 22mm water resistant floorboard.
The external walls of the basement were lined with 75mm timber frames and fitted with 75mm rigid foam boards. The internal walls were battened out using 50mm x 25mm timbers.
We also installed a new timber staircase.

A toilet area was formed under the stairs, supplying a new WC and basin. The foul waste collects in a chamber within the utility room and discharges into the nearest foul waste drains externally.
The ceiling received a 100mm wool insulation and all surfaces were then lined with a 12.5mm plasterboard.
The rooms were fitted out with a softwood skirting board. New doors were fitted to both the living area and utility room.

  1. Fixing to or through the waterproof systems

When fixing through the membranes, careful consideration was taken, including the possibility of an alternative method.

  1. Non-earth retaining walls

We carefully marked the position of the fixing at the required point and drilled. We filled the hole with a high quality mastic and then inserted a propitiatory plastic fixing plug. More sealant was applied around the hole to form a seal before inserting the screw.

  1. Earth retaining walls

Specialist fixing plugs with purpose-made seals were used in order to maintain the integrity of the membrane.

It is important that the flushing/service points are easily accessible so that regular maintenance can be carried out to the drainage system to ensure that no blockages occur. Maintenance programs are available and are a condition of the guarantee.

As the works described involve a Party Wall, the Party Wall Act 1996 was therefore applied. This requires the owner of a property to notify his/her neighbour(s) of the proposed works and obtain the neighbours’ consent. A neighbour cannot unreasonably withhold consent, but should you require further advice or information, please initially contact our office or a suitably qualified party wall surveyor.

Danford Brewer & Ives are very aware of Health & Safety issues and dangers within our industry. Any work that we carry out is done so safely, in the best interests of our customers, the general public, and ourselves.

Guarantees

Upon completion of our specialist remedial works and full settlement of our final invoice, Danford Brewer & Ives issue a 10-year independent insurance-backed guarantee.

The client was thrilled with the final results and tells us the children are using their new playroom all the time.  If you have any plans to convert your basement into additional living space then contact Danford Brewer & Ives for expert advice and support.

Here is a short video showing how the project progressed and finished up.

https://www.youtube.com/watch?v=461GGEh6QMg