How to build timber ceiling for rear deck on Queenslander?

[Traveller]

Looking to install a timber (or look alike) ceiling into rear deck on Queenslander, which has four different slopes. Have to make it possum proof. Rafter spacing approx 900mm. Approx 300mm space for soffit (none installed). Foilboard insulation installed, which has made deck usable in summer, but intend to add some more rockwool or similar. Looking for advice on suitable cladding products, and how to install. My thoughts so far:

soffit - too hard to use timber product, so thinking colorbond flat sheet screwed direct to rafter on slope and hope it doesn't sag too much. Note: fascia board groove is partly obscured by rafter, which I could chisel out to make soffit slip inside groove. could screw timber block on fascia at rafter mid point to support soffit, but hard to do on roof beam as second floor deck means everything must be done from the deck.

cladding: Permawood, perhaps pine (Bunnings site says indoors), ply (might be heavy for me to lift)

how to support cladding: thinking metal "top hat" as used for ceilings at 450 centres, and notched to sit flush with rafter. Two fixings per rafter. (?can I nail cladding into this metal top hat?). This would make the cladding run the same direction as the rafters. Is there another solution?

I'm used to working with timber, but thinking I might need to buy a sliding drop saw and nail gun.

[JacobZ]

Hi @Traveller,

Thank you for your question and welcome to the Bunnings Workshop community, it is brilliant to have you join us.

This looks like a fantastic project which I am excited to see get underway.

I have a few questions I'd like to start with so our community members can get a better idea of what you'd like to achieve.

Is it possible to get some photos of the soffit that you are referring to?

When you say you'd like a timber ceiling, is the aim to have exposed grain that can be stained to match the doors and windows? Or is the idea to have a woodgrain look that is painted? Or a prefinished product that looks like wood?

All options are possible, but the choice will come down to personal preference.

Some options that might be good for you include: 

• 140 x 12mm Lining Board Pine or Marine AA Grade Plywood for the exposed grain look that will require staining and sealing.
• Duraplank Woodgrain Fibre Cement Weatherboard or Woodgrain HardiePlank™ Weatherboard for woodgrain fibre cement products that will require painting.
• QuickBoard Cedar PVC VJ Wall and Ceiling Lining Board or QuickBoard Tas Oak Castellated PVC Composite Timber Wall and Ceiling Lining Board for a prefinished timber look.

With battening out the ceiling, there are two options I see that have pros and cons.

There are metal ceiling battens such as Siniat 22 x 6100mm 0.42bmt Cyclonic Batten, which are lightweight and easy to install, but you would require either screws or specific hardened nails (Paslode Steel Frame Brad) which can be quite pricy.

The other option is to simply use framing timber such as this 70 x 35mm Framing MGP10 H2 Blue Pine, which is going to be heavier than the metal battens but will mean you can use standard brad nails to fix your lining to them.

The weight of the materials is also certainly something to take into account. You might like to look into hiring a Panel Lift to make the job easier.

Allow me to tag some of our helpful members to see if they have any ideas, @Jewelleryrescue, @Noyade, @DIYGnome, @prettyliving.

Let me know if you have any further questions.

Jacob

[Traveller]

JacobZ, Thanks for the information. I attach a few more details, including a sketch plan of the area, and photos of the "soffit" area. I've looked into some of the suggested products - the quick board installation guide prohibits installation within 300mm of roof, so it won't work and I want timber look in a natural colour, so FC planks are not suitable. Plywood and pine lining boards are the remaining options, although for completeness, we might also consider VJ board, painted, as that would match our internal ceiling.

I might buy a length of the metal batten and get a feel for difficulty of screwing into this. If I use the timber lining board over metal battens, can I conceal fix using screws (I'm familiar with concealed nailing)?

What spacing is required for the battens to support the weight of the timber?

I expect to need a timber bead on all edges - can this be created by using the inevitable timber lining board offcuts?Sketch plan12345

[JacobZ]

Hi @Traveller,

Thanks for the additional images and information.

I'd probably narrow your choices to between the VJ and the pine lining purely for their ease of installation being tongue and groove products.

Pine lining can be finished using a clear oil or varnish to keep an exposed timber look, whereas VJ board will come pre primed for ease of painting.

The metal battens are easy to work with and screws will drive into them quite easily. They should be attached at 450mm centres similar to the spacing of a stud wall.

Screws can be concealed by countersinking them and applying plaster over the top, but this would be difficult with the exposed timber look as any filler used will likely stand out.

You can use brad nails to attach materials to steel battens, but depending on the thickness of the steel, you may need to use a hardened steel nail such as these Paslode 15G x 38mm Steel Frame Brad. Using these nails will still give a solid connection when used in conjunction with adhesive and will be much easier to conceal than screws would. 

You could certainly use offcuts to create a timber bead by ripping them down with a table saw, circular saw or track saw, but this would definitely take a lot of time. It would probably work out cheaper and easier when all things are considered to simply use a piece of dressed all round timber in a profile of your choosing.

Let me know what you think and if you have any other questions.

Jacob

[Traveller]

Jacob, good discussion, thanks. Some further questions:

1) with the pine boards that come in fixed 1200mm lengths, how should they be installed? I'm familiar with decking in random lengths that I've cut to have joins on the joists. I'm wondering if joins need to be supported, and if the joins should be staggered?

2) there is a difficulty with the detail at the fascia, as the bottom of the fascia is only about 20mm below the rafters. Originally I thought the metal battens could be notched to sit flush with the bottom of the rafters, or alternatively much more work, would be to install timber noggins between the rafters (cut to size and skew nailed). Timber or metal rafters sitting proud below the existing rafters are easy to install, but the lining would then sit below the fascia - possibly that could be weather proofed with an angle flashing but interested in any other ideas. Alternatively, I calculated the weight of the timber lining and it is light at around 20kg per bay (between the rafters, 900mm centres and max 3.6m long, with some bays shorter). So question is whether new "battens" could run parallel to the rafters, and flush with the bottom of the rafters? For example, run 70x35xmax 3.6m long parallel to rafters, supported at ends by roof framing (and if insufficient support, perhaps a noggin halfway).

3) and is there a thicker lining board that would span the 900mm without installing intermediate battens?

[JacobZ]

Hi @Traveller,

Is it possible to get some dimensions for each of the different ceilings?

I ask because, it is likely possible to order lengths of pine lining, such as the 138 x 12mm 4.8m Pre-Oiled Clear 302 Laminated Pine Lining Board that can span the full ceiling so there'd be no need for any joins.

If you have to do any joins, the idea would be the same as a deck that your joins should sit directly over a batten or rafter so the end can be supported with a mechanical fixing and that they should be staggered so there aren't any lines of weakness.

When you can't use a batten because of the height of the fascia in relation to the rafters, I think the only simple solution is to add noggings. I understand it will be a fair bit of work, but the only other idea I can think of is to replace the fascia with a wider board so that it hangs lower and covers the edge of the timber.

Unfortunately, I'm not aware of a lining board that the manufacturer is comfortable being installed as a ceiling with fixings at 900mm spacings.

I think the best way to go about this is to install blocking to the existing rafters so you can ensure there are fixings at 450mm spacings in the direction that you want. It will be a fair bit of work, but unfortunately, with the height issues caused by the fascia, it might be your only option.

Let me know what you think, I'm happy to brainstorm more solutions with you if required.

Jacob