Site Conditions

Ideal fitting environment

Prior to the work commencing all wet trades should be finished and the site should be closed and dry with the heating on.

All new plaster, screeds etc should be dry.

It is advisable for all other trades to be finished including decorating to insure that the new floor is safe from damage after installation from workmen and tools.

The environment (humidity and temperature) to the rooms should be as close as possible to that expected when the building is occupied.

The work area should be empty of all items apart from your tools and materials.

Installation over a concrete or screed slab

As a rule of thumb, it takes 4 weeks for the first inch of floor screed to dry, 4 weeks for the second inch of floor screed and 6 extra weeks for the 3rd inch. (i.e. 8 weeks drying time for a 2 inch screed and 14 weeks for a 3 inch screed).

Cathedral Flooring can be successfully installed over a concrete or screed slab under certain conditions.

The slab must be dry flat and trowel finished. (See test guide by NOFMA)

A trapped hygrometer test is a good way of testing the screed for the degree of dryness. Any damp or moisture source of any kind should be eradicated. All plumbing should be checked for leaks. Hot pipes below the new wood floor should be insulated. Sources of heat under the floor should be diffused if possible. Any pipe work unfinished should be pressure tested. Heating should be commissioned for at least two weeks before fitting commences. The temperature and humidity of the building should be equal to the conditions of occupancy during and following the installation i.e. 40-55%.

The existing floor surface should be flat with inaccuracies of not more than 3mm in a 2400mm span. If this is not follwed you may find that the floor bounces and does not sit flat. Providing this is not too bad it may eventually settle.

The flooring to be laid must not be exposed to excessive periods of high humidity or moisture.

After installation and during the first 2 months of occupancy the heating should be kept at a suitable level high enough to keep moisture levels low but low enough not to reduce the floors moisture content to rapidly as this may encourage distortion in the boards.

In joist construction to ground floors without a basement, outside cross flow ventilation through vents in the foundation walls must be provided with no dead air areas.It is advisable to insulate between the joist.

Tests for moisture in a slab as published by N.O.F M.A

The rubber mat test
Lay a smooth bottomed rubber mat on the slab. Place a weight in the middle such as a bucket of sand. Leave for at least 24 hours. If when the mat is removed there is a dark patch, to much moisture is present. This test is worthless if the slab surface is other than light in colour originally.

Polyethylene film test
Tape a one foot square of clear polyethylene to the slab sealing the edges with moisture resisting tape. If after 24 hours no condensation is visible the slab can be considered dry enough to lay the floor.

Calcium Chloride test
Place a quarter of a teaspoon of Calcium Chloride crystals in a 3 inch diameter putty ring on the slab. Press a glass into the ring to form a sealed containment. If the crystals dissolve within 12 hours the slab is too wet.

Phenolphthalein test
Put several drops of Phenolphthalein solution in grain alcohol at various spots on the slab. If a red colour appears in a few minutes, to much moisture is present.

Hygrometer test
To test that the floor is dry enough to lay a wooden floor you must do a trapped hygrometer test. Place a hygrometer on the floor directly on top of the screed, cover with polystyrene blocks, cover again with plastic and tape to the floor. After 12 hours check the meter. If the reading is over 75% the floor is too wet to lay. Do this test on at least 2 areas of the floor. Doing this you are measuring the escaping moisture.