Installation of the Wooden Slab of a Wooden House

Summary

    – Step 1: Install the bottom rail

    – Step 2: Install the rim joists and the joists on the header wall

    – Step 3: Install the joist

    – Step 4: Install the wood floor

The construction of the slab is an essential step: it conditions the whole geometry of the house. This slab can be poured into concrete or wood. The wooden slab has the advantage of being a dry technique, quick to install. It is mounted on the cinder block foundation. 

The wooden slab is formed by an assembly of joists on which wooden plates are fixed. The installation of the slab requires solid technical knowledge and precise work.

Follow this step-by-step guide to install the wood slab of your wood construction. 

Materials needed to lay a wooden slab for a wooden house.

Dowels 

Nailer 

Man head nails 

Tape measure 

Spirit level 

Wood saw 

Circular saw 

Clamp 

1. Lay the bottom rail

The bottom rail is the first piece of wood placed on the masonry. It must be perfectly horizontal because it is the element on which the house’s structure rests.

Caution: the bottom rail should not be placed less than 20 cm from the ground. Adjust the height of the foundations to ensure that the wooden slab is out of the water.

    Install a bituminous strip (waterproof) on all the peripheral and partition walls. It will isolate the bottom rail from rising damp (by capillary action).

    – Lay the autoclave wood bottom rail flatly on the bituminous strip along the entire length of the foundation.

    – Check its horizontality every 60 cm. The tolerance is +/- 1 cm on all foundations.

    – If necessary, cut and install wooden shims (the width of the rail) on the bottom rail to restore the level.

Good to know: use solid shims that you buy in different thicknesses to correct the height.

    – Fix the bottom rail with 100 × 8 mm metal plugs every 2 m.

Good to know: drown the heads of the fasteners so that they do not protrude from the bottom rail.

2. Install the rim joists and the joists on the partition wall

Place the rim joists.

    – Position a rim joist over the entire perimeter structure. The rim joist is a piece of wood attached perpendicularly to the bottom rail surrounding the wood slab.

    – Hold the rim joist to the sill plate with large clamps.

    – Nail it in place.

Place the joists on the partition walls.

    – Fasten a joist to the header walls, perpendicular to the bottom rail.

    – Nail it at each end to the rim joist.

3. Install the joist

The distribution of the joists is calculated according to the cross-section of the wood and the dimensions of the wood floor panels (a panel must rest on at least 3 supports).

Caution: the support surface of the joists on the bottom rail must be at least 50 mm.

    – Fasten the joists at regular intervals by nailing them to the edge joist, using 2 nails of 120 mm per joist.

    – Fasten the joists to the header walls using connectors pegged to the walls.

    – Attach spacers between each joist to stiffen the structure.

    – Apply a polyurethane seal around the slab, between the bottom rail and the edge joist. 

4. Install the wood floor

The joists must form completely flat support to avoid the floor squeaking.

Good to know: place a strip of insulating felt on the joists to prevent the risk of squeaking between the beams and the floor.

    – Place the first panel at a corner of the floor, perpendicular to the joists and 3 support points.

    – Fasten the panel with nails every 15 cm on the periphery (edge joist) and every 60 cm on the intermediate supports (joists).

    – Install the following panels perpendicular to the joists and with staggered joints.

Good to know: use OSB-type panels with tongue and groove, which allows the panels to be interlocked.

    – Cut the wood panels if necessary with a circular saw.

Read more:

• Why Choose Wood Framing for Your House;
• How to Treat Exterior Wood.