Add an upstairs floor

It will frequently happen that your ruined property or barn in France will have an exterior shell but no internal walls or 'upstairs', so it will need a whole new first floor adding (or replacing).

To add a new floor using exposed beams is practical and attractive, but it is quite a large job. In principle you are simply going to build the new floor with your (hopefully reclaimed) beams, and leave the beams visible rather than plasterboard the underside.

If you are starting from nothing you can put plasterboard on top of the beams, so that from below you have a 'proper' ceiling on top of the beams. Go the whole way, and paint the plasterboard first - much quicker than painting it in situ.

Before you start you will need a structural engineer or similarly qualified prefessional to tell you what size of beams (cross-section for what length of beam) to use for your particular floor size, and the spacing between them - 60 centimetres is common.

These new beams can then either be set into holes made in the wall, or supported by brackets that are firmly fixed to the wall. Whichever method you use, these are critical points for the strength of the floor, and must be as defined by a suitably qualified person.

It is sometimes said that beams set into the wall itself are more likely to be affected later on by problems of damp, because of the natural humidity in the wall being absorbed by the wood.

The problem is largely one of getting the level exactly right across the whole area. With carefully fitted brackets it will be reasonably easy, but holes in an old stone wall are rough and ragged. Wedges of wood should be used to hold the floor level in position until the spaces around the beams (the holes will inevitably be a bit larger than the cross section of the wood) are refilled.

Lifting the beams into place will be a very heavy job (needing a hoist), so it is probable that you will need professional help with this.

If the beams are to left exposed you should specify that sanded wood be used for all the visible faces, rather than rough 'building' wood.

After the beams are in place, the rest of the job is straightforward. It is simply a matter of choosing what level of sound insulation you want between the two levels of the property and constructing the floor. Typical options for the floor itself (materials in order starting from the bottom of the floor):

Option 1

plasterboard, to be visible as a ceiling from the downstairs rooms, then chipboard, ideally 22mm thick, tongue and groove; then sheets of sound insulation eg thick felt sold specially for the purpose; then flooring parquet

Option 2

strips of sound insulation along the tops of all the beams (this sound insulation is sold in strips 6cm or 7cm wide), then plasterboard, tongue and groove chipboard; then sheets of sound insulation eg thick felt sold specially for the purpose; then a second layer of chipboard, tongue and groove; then thin 'polystyrene' type sound insulation; then flooring parquet. This works well but is overall quite heavy!

Option 3

Simply fit floorboards straight to the beams! This is the traditional approach but offers little protection against sound passing between the two levels of the property. You will need good, solid, real wood floorboards to cross a 60cm space between the beams. Thin wood will bow, bend and creak when someone walks on it.

Under all plans, leave the materials for the floor in the environment in opened packets for a few days before starting work so they acclimatise, and leave an expansion gap around the edge of the floor, otherwise when the temperature changes and your floor expands it will start to warp, creak, get noisy and crack!