Crown Cornice

Crown cornice incorporating hidden picture hanging system and pelmet

[updated to as-built]


1. Crown cornice showing picture hanging track

Construction

A 185mm x 18mm FJ pine trim board will form the baseboard on three walls and the pelmet on the fourth window wall. The bottom of the baseboard will be 203mm (185mm + 18mm) below the ceiling and it will be attached using masonry anchors long enough to go through the board and render and anchor to the stone in the wall. The baseboards will be rebated to fit a readily available extruded aluminium sail track profile that will be attached to the baseboard from behind prior to installation. This will form the track for the hidden picture hanging system. An off-the-shelf cornice moulding profile, in this case Boral's "Sydney" machine extruded paper-wrapped plaster product, will then be installed as shown. Finally, to add to the overall profile and to hide the masonry anchor points, a strip of panel moulding will be brad nailed without glue to the front of the baseboard below the cornice moulding, as shown.

Removal (in theory)

The panel moulding strip can be pryed off to expose the masonry anchor points. The cornice is then removed using standard techniques to expose additional anchor points. The removable type anchors can then be withdrawn and the baseboards detached from the wall.

Anchors

I want the anchors themselves to be removable, otherwise the walls could be damaged excessively if removal is ever required.

The stone is basalt "bluestone". Previous attempts to drill into it using a normal masonry bit and hammer drill failed. A wet diamond method succeeded and produces a very clean hole but is very slow and the mess needs to be managed. An SDS+ hammer drill and bit that I bought for this job for AU$99 (Ozito) performed best of all and was very quick in test.

My DIY hidden hanging system

Commercial gallery hanging systems provide a wall or ceiling mountable aluminium channel from which hanging wires can be suspended. I needed a channel that could be attached to the cornice or baseboard itself simply to minimise drilling into the wall or ceiling. There are commercial systems that would allow this, including one hidden system. The most expensive components are the hangers themselves. The wire, either steel or nylon, is less expensive to buy in bulk. The quick adjust hooks are available separately so the only tricky component is the attachment piece at the top of the wire that goes in the channel.

Commercial hanger wires should work. A barrel clamp can also be used provided it fits into the channel (8mm diameter or less).

2. Cheap DIY hanger wire "barrel" clamp

Overall with channel, drop wires and adjustable hooks, my DIY system should cost about half that of the least expensive commercial system I've found. It is about a third the cost of the only commercial hidden channel system I've found.


3. Pelmet detail

Pelmet (full width of room)

The critical component of the pelmet is the horizontal baseplate to which the curtain tracks will be attached. It sits flat against the ceiling and is anchored through the ceiling plaster and into the joists above using long timber screws. To avoid drilling many holes searching for unequally spaced joists from below, a "story" stick was used to mark the joist centres for both rooms from above in the roofspace.

Note that the wall baseboards don't extend all the way to the ceiling, and the pelmet top plate doesn't go all the way to the wall. This is because the render is uneven where the walls meet the ceiling. It also means I can achieve the 200mm projection for the built-up cornice and pelmet using 185mm wide boards. Similarly for the pelmet baseplate to achieve a 200mm internal spacing between the pelmet and the wall to facilitate two layers of curtain, a light shadow curtain and a heavy curtain. The 18mm gaps will not be visible once the coving is in place.

Baseboard rebating

To produce the rebating to fit the sail track profile I first tried using the router table and a standard square bit but this was going to require many passes for each rebate and on my equipment it was also difficult to control the accuracy and the finish. I then moved to the table saw where is was possible do the entire profile using four lengthwise cuts. The sequence of cuts shown below minimised the material the blade had to remove, making it easier to handle. Contrary to the images, the rounded edge was routed after the rebating was completed.

Tip: Keeping the waste side of the cut towards the guide (imagine the guide is to the left of the piece and the table at the bottom) ensures that any movement of the piece away from the guide moves the blade into waste material and not the finished piece.

4. First cut

5. Second cut

6. Third cut

7. Fourth cut

Costing

Crown to walls

Baseboard: 185 x 18 mm x 5.4m x 5 @ AU$9.35 per metre

Sail track: 3m x 7 @ AU$7 per metre

Cornice moulding: 4.2m x 6 @ AU$5.70 per metre

Cover moulding strap: 20 x 5 mm x 2.4 x 7 @ AU$3.75 per metre

Total: AU$606

Pelmet with crown

Pelmet baseplate: 185 x 18 mm x 5.4 x 2 @ AU$9.25 per metre

Pelmet cove: 30 x 30 mm x 2.4 x 4 @ AU$4.60 per metre

Baseboard: 185 x 18 mm x 5.4m x 2 @ AU$9.35 per metre

Cornice moulding: 4.2m x 2 @ AU$5.70 per metre

Cover moulding strap: 20 x 5 mm x 2.4 x 4 @ AU$3.75 per metre

Total: AU$330

Miscellaneous materials

Anchors and other fixings: AU$50

Cornice adhesive: AU$15

Labour

I estimate it would require two skilled people using specialised tools two to three days to supply, setup, cut, assemble and install the pelmet plus full built-up crown cornice incorporating the hidden hanging system to both rooms. Therefore three days minimum, or 24 hours.

Assuming a labour rate of AU$100 per hour combined (GST inclusive, circa 2020), i.e. AU$2400.

Total value

AU$3400