Timber worksurface Installation Guide

Section 5: timber worksurface installation

5 . 1 Work surface fixing method

a) slotted brackets.

The tops are fixed down using slotted stretcher brackets only (with slots uppermost). The crossgrain slots in the brackets, together with round head screws, will accommodate the natural movement of the timber whilst holding the work surface down. Use typically 2 brackets per end panel on 560 – 570mm deep base units at 500 – 600mm centres. Deeper units will need more brackets pro-rata.

Bracket fixing

Fix the brackets to the base unit side panels only. (The top rails are not strong enough). Use 4 x 15mm Rttd screws.

b) Units with top panels

On units that have a full or partial top panel, fix the brackets directly under the panel, having first drilled 15mm minimum access holes through the top to line up with the crossgrain slots in the brackets. Use a 4 x 35 – 38mm Rttd screws to fix through the bracket and unit top into the timber.

Note:

These top panels must be drilled or cut out over at least 50% of their area to allow the underside of the timber work surface to breath and stay in balance with the upper surface.

c) Above appliances

Where the tops span appliances alone, or are unsupported into the corner, cut and fix timber wall rails to support the tops and attach the slotted brackets. Tops that span two appliances side- by-side must be supported.

• either by a mid panel fixed between them
• or by a solid timber front rail at least 40mm high and fixed across the span.

d) Onto masonry features

Do not fix wooden tops directly into masonry. Fit them over timber spacers 6 – 10mm thick, which are themselves on a Damp Proof Membrane (DPM). This prevents the transmission of moisture and provides an airspace under the top.

Appliance moisture barrier & upstand

5.2 Appliance moisture barrier

Fit moisture barrier to protect the underside of the timber worksurface from heat and steam produced by built-under washing machines, dishwashers and microwaves. The barrier comes in sheet form. Staple or tack it to the underside of the top from just behind the capillary groove extending to the back edge and sideways to overlap the adjacent units.

5 . 3 Upstand

This comes in 3m lengths. Longer pieces can be made by scarf jointing and glueing the shorter pieces together.

Upstand for Work-surface Blanks is supplied to fit 40mm thick tops. It must be cut down and re-smoothed to fit 27mm tops.

Upstand for 60, 80 & 100mm thick worksurfaces comes with the extension pieces to make it up to the appropriate thickness at the ends where it will be visible. The pieces become loose, ready to joint with biscuits and PVA glue, onto the left and/or right hand of the upstand length(s) as appropriate. Dress the faces of the joint and refinish as necessary, after the glue has dried.

Either fix upstand to the rear edge of the top or, if this will make top assembly hard to move into place, the upstand can be fixed to the wall behind. Seal the joints with clear low modulus Silicone sealer.

Note:

The latter method is unsuitable for use with counterback units.

Sealing corner joints & fixing down tops

5 . 4 Sealing corner joints

Make sure any endgrain has been sealed before assembling the joints, (See section 2 . 14a)

Apply a light bead of clear low modulus silicone sealer along one side of the joint, just below the top surface and edges. Align the two sides with biscuits before clamping up firmly with worksurface bolts. Wipe of the surface sealer.

5 . 5 Fixing the tops

For Belfast sinks, just before the worksurfaces are to be put in place, run a bead of low modulus clear silicone along the outer half of the sink rim, at the sides and rear, to form the primary seal to the worksurface. Move the tops into place. Use thin pieces of board as temporary packing to position them with 4 – 5mm expansion gaps between the edges and ends of the tops and the walls.

Pilot – drill at the centre of the crossgrain slot.

• use 04 x 20mm Rttd screws when fixing directly to the worksurface
• use 04 x 35 – 38mm screws when fixing through brackets and units with tops. (See Section 5 . 1b above).

Tighten the screws fully, then just loosen them by turning back a quarter turn. This stops the screws binding against the brackets and allows the wood to ‘move’.

5 . 6 Cupped tops

If a timber top is cupped, due to moisture differences on the site between the opposite surfaces of the wood, it should be fixed down through the rear brackets first. Then gently and gradually, using clamps and battens, pull it down at the front before fixing it there with screws. Allow time for the timber surfaces to equalise and flatten, otherwise the timber may be split.

5 . 7 Undermounted sink installation

a). The narrow strip of worksurface between double sinks must be reinforced with a timber rail. Fix the rail using a method that allows the worksurface to ‘move’ while it is being supported.

b). Run a medium sized bead of clear low modulus silicone around the rim of the sink, offer it up and fix it under the cut-out with sink clips.

c). On undermounted and Belfast type sinks, with 27 & 40mm worksurfaces only. Add more silicone as required and form a smooth cove between the inside of the sink and the underside of the worksurface all round the opening.

5 . 8 Lay – on appliance and sink installation

Fit lay – on appliances and sinks according to the manufacturer’s instructions using the sealing materials provided by them. With lay – on sinks, if no seal is supplied, use a generous bead of clear low modulus silicone between the sink rim and worksurface.

5 . 9 Wall seals

Form a seal between the work-surface, upstand and adjacent walls with clear low modulus silicone. If the walls are to be tiled, place a temporary spacer on the work-surface to form a 3 – 4mm gap across the bottom of the tiles. After tiling and grouting seal the gap with low modulus silicone to stop moisture and allow timber movement.