Double Dutch Floor Laying

Double Dutch when it comes to floor laying

We were recently instructed by a shop fitting outfit to investigate the floors of a commercial property in Coney Street, York occupied by The Rituals, home and body cosmetics store. The shop was recently refurbished just before Christmas 2012 which involved the laying of a bespoke parquet floor fitted by a specialist flooring company from Holland.

Shortly after the refurbishment the shop owners noticed the floor had started to move and a bump occurred where the floor was beginning to lift. Sure enough the expensive parquet floor lifted and the Dutch company returned to investigate. Part of the floor was removed and then re-laid, and the flooring company concluded that movement had occurred as the concrete floors beneath were damp, nevertheless they carried out the repair.  

Images showing areas where the floor had lifted and delaminated from the concrete floor structure.

Not convinced and worried about a reoccurrence, Dryfix were invited to investigate the condition of the timber floor coverings and the solid concrete floor structure and provide professional advice on why the issue occurred and how the problem can be prevented in the future.

The building is a three storey terrace property situated in the heart of York, the building like many others in York benefits from a basement. To the front of the shop the basement is vaulted brickwork with a suspended timber floor to the rear. The basement was inspected and sure enough was damp, although to be expected of a room below ground level. The rear section of the ground floor is suspended timber construction which had been replaced during the refurbishment due to decay and infestation of the original timber floor. As an attempt to prevent damp within the basement presumably affecting the ground floor the company had lined the basement walls with a visqueen membrane. Above the vaulted cellar a new concrete floor had been laid which incorporated a damp proof membrane protecting the floor slab from damp.

Images taken onsite left – right showing; Damp proof membrane visible between cellar and ground floor concrete floor slab, decayed and infested original joist end left in situ, movement of the parquet flooring, suspended timber floor to the rear of the shop, membrane applied to cellar walls, sweating of the membrane within the cellar.

Readings were taken across the parquet floor covering using an electronic moisture meter, which revealed the moisture content of the floor covering was acceptable. Further readings were taken electronically using radio waves through the floor covering into the concrete floor substructure which were also low. Timber is a hygroscopic material which will readily absorb moisture from the atmosphere or where in contact with a damp wall or floor, this can result in the moisture content of the timbers reaching levels where they become vulnerable to decay and insect infestation. High moisture levels recorded in the timbers would give the indication of additional sources of moisture possibly from damp surroundings. The low readings taken revealed the moisture content of the parquet floor and substructure were acceptable therefore it is doubtful the concrete floor was damp.

Readings taken onsite form the floor surface using resistance meter – measurements shown as actual Wood Moisture Content (WMC), readings taken using radio waves through the floor structure, resistance readings taken from the concrete floor using insulate probes, results from calcium carbide test. 

From our non destructive investigations we found no evidence of dampness affecting the floor covering, however in order to conclude our findings a disruptive investigation was undertaken which involved carefully cutting out a section of the parquet to allow the moisture content of the concrete floor to be analyzed in detail using a calcium carbide meter.

The results given from samples of the floor test were also low indicating the concrete floor was also dry which was expected due to the damp proof membrane laid beneath the floor protecting the floor and coverings from the damp basement.

 So why had the floor moved?

A further investigation also revealed additional areas of the floor covering had also started to lift and delaminate from the adhesive used to bond the parquet to the concrete floor.  In light of our investigations delamination had not occurred due to dampness, so there had to be another reason.

Refurbishment of the property was undertaken quickly and the flooring was brought over from Holland and laid immediately, therefore there was no time for the parquet to reach equilibrium with the surrounding environment. As previously mentioned, timber is a hygroscopic material which will vary in moisture content with the surrounding atmospheric conditions. This hygroscopic ability can cause timber to expand and contract until it reaches fiber saturation point. Prior to laying any solid wooden flooring it is essential that timber is kept within the environment for at least 7 – 14 days to allow the wood to reach equilibrium,  failing to do this may result in the wood moving in according to the conditions after being laid. In addition, during refurbishment of the building the atmospheric conditions would be less than stable due to building work involving recent plastering, decorating an cleaning which will affect the ambient humidity. In this scenario the conditions should have also been stable before laying the floor.

When a sample of the parquet was removed the bond between the concrete and the adhesive was also poor, probably as a result of dust and debris created during the work and poor preparation, this again will contribute to the potential of the floor lifting.

Almost three months after refurbishment, it is not expect the floor will move much further although the poor laying of the floor may cause further lifting of the parquet in the near future so additional repairs are expected in the future or removing and relaying the floor considered. Although not directly associated to the floors condition it was recommend the plastic membrane applied to the cellar walls and floors is removed to prevent sweating which could affect the suspended timber floor at the rear of the shop in the future. The decayed joist ends left in situ from the original floor should also be removed to prevent the possibility of a fungal outbreak or infestation of the new timbers.

Thanks to our expert advice our client has an answer and solution to the problem evolved through accurate diagnosis and investigation.

When in need of advice please do not hesitate to call the experts “Yorkshire Leading Damp and Timber Specialists” Dryfix Preservation Ltd

Many thanks

Russell Rafton

C.S.R.T. / I.S.S.E

Dryfix – Surveyor

www.dryfix.net

 http://www.rituals.com/uk-en/home/index