How to build an external window frame?

[BoeingFan]

Hi All,

A while ago my builder and I halted our renovations due to a lack of funds. We fitted a tall narrow stained glass window, which my Mum made, in between the timber frame (studs). Until now, I've just filled in the gap around the window frame with paper towels and packing tape on the outside to block the weather and insects. 

So, I'd like to install a simple hardwood frame; could you please help me understand what to do here? What wood can I buy from Bunnings? I would just like to get a hardwood plank cut up and have the two sides plus the top and bottom screwed into place, painted and caulked. Do I put screws in through the external window frame to the studs as well as into the stained glass window frame, just the stained glass frame, or just the studs? Do I remove the chock once I have other sides screwed into place?

I will paint the raw cement sheet before installing the frame. 

Thanks,

Jason

[EricL]

Hi @BoeingFan 

If the builder has fixed the window permanently in place, the timber wedge can be removed. I suggest spraying the inside and outside gaps around it with Parfix 340g Expanding Foam Filler. This will fill in the gap and you don't have to use the paper towels anymore. The expanding foam will come out of the gap, and I recommend waiting for the foam to fully cure before you trim it with a Craftright 18mm Snap Off Knife. To further seal off the window I suggest using Sika 310ml Grey Concrete Sikaflex Pro+ Polyurethane Sealant on the outside and inside trim of the window. But if the gap is more than 5mm in width you'll need to use a timber trim to fill in the gap

In regards to the trim, you can use spotted gum, merbau, black butt and ironbark. There is also the 42 x 18mm 5.4m Moulding H3 Treated Pine FJ Primed 4 Edge Pencil Round LOSP. This is treated pine and just needs to be cut down to serve as window trim. I suggest making sure to paint the cut ends to protect it from the weather. Please keep in mind that you'll need to cut this at home as the store saw will not do precision cuts. Once you've cut the timber to the correct size you can then glue and screw the pieces to the outside of the window. I propose using Selleys 320g Liquid Nails Construction Adhesive and Zenith 8 - 10 x 40mm Galvanised Countersunk Rib Head Timber Screws.

I suggest putting on more Sikaflex on the outside and inside of the trim to fully seal it in place.

Let me tag @Dave-1 and @Nailbag for their recommendations.   

If you need further assistance, please let us know.

Eric

[Dave-1]

Good morning @BoeingFan 

I was going through your questions and @EricL's answers pretty much cover them.

Some other questions

- I would screw through the trim into the studs and also into the window frame. (My thinking is to make sure its joined) predrill through the cement sheet. (It looks like fibro so be aware of asbestos)

- Is the chock doing anything, as in holding the window in place? If the builder has secured the stained glass frame it really shouldnt be needed?

- Do you want 45degree corners or are after a straight edged corner? Depends on what your other windows look like is how I would approach that.

Dave

[Nailbag]

Hi @BoeingFan 

The steps @EricL is basically already how I would approach this. First you need to fix the widow to the side timber studs (vertical frame timber) with screws as @Dave-1 mentioned or nails both pilot holed first through the window frame.

Go sparingly with the expanding foam and read the instructions. Most expand 10-15% of what you apply. Once dried, you can cut the excess with something like a bread knife is ideal flush to both the inside and outside of the window frame.

Ideally you would then put internal wall panelling on the left side of the window to match the right. Then install the trim's @EricL mentioned to cover the gap between the window and the wall. This is called architrave. 

Nailbag

[BoeingFan]

Thank you so much @EricL @Nailbag and @Dave-1 

There are 4 nails in the inside of the window frame going in to the studs, 2 on each side, 1 at the top, 1 at the bottom. The builder has told me to leave the chock in place, but I'm inclined to punch the nails in flush, then remove the chocks and see if it stays in place 🤞

So today I bought some 64mm x 19mm spotted gum hardwood, some gap filler, a caulking gun, and a handsaw. 

• I didn't buy the expanding foam because I'm nervous as hell that I don't know how to use it and the place will look like an exploded laundromat with foam everywhere. 
• I also hadn't seen the @EricL's post before shopping, and bought No More Gaps Exterior (White) instead of the Sika 310ml Grey Concrete Sikaflex Pro+ Polyurethane Sealant. Is there a particular advantage to the Silka over the Selleys? I notice the Silka states, "...is designed for movement and connection joints in concrete and masonry facades." The gap filler will be used between painted timber planks, and painted timber and painted fibro, so will the Selleys be as effective?
• In relation to your question @Dave-1 about 45º angle cuts; I think this would be great but I'm a nervous novice. Perhaps I could try some cuts with my sliding drop saw on some old bits of timber out in the back yard. I do like the idea of the 45º corners. 
• My builder told me to put the new external frame 3mm from the inside of the window frame to give it a 'quirk'. This will be exciting. The yard will look like a sawmill whilst I get this down pat. 

The first thing I will do is paint the 'raw' fibro with Dulux one step prep on Saturday, then the rest can begin. I look forward to any followups you may have to what I've written above, and as always I'm very grateful for your help.

Cheers,

Jason

[EricL]

Hi @BoeingFan 

Let me tag @Dave-1 to make sure that they see your question. Remember that the best way to find out how things work is to test it first. You can always grab a can of expanding foam and do a small test on piece of timber to give you an idea of how it works. Selleys No more gaps exterior will do just fine and provide the same amount of flexibility. My best advice is to add extra screws to the window frame close to where the nails are to prevent movement. Practice first with old timber offcuts to get a feel for the cuts and where the cuts should be placed.    

If you have any other questions we can help with, please let us know.

Eric

[Dave-1]

Good Evening @BoeingFan 

Nice work on sourcing the bits you want, even better that you have a drop saw as it makes life soooooo much easier and believe me its FUN when you see what you can do, the 45deg angles are just a start!

As @EricL has suggested, test it out on some offcuts, and by testing it out I actually mean cut 4 of offcuts to form a rectangle as one thing I would consistantly get wrong in my head was which way the angle needed to be When I was making up my outside table I actually made timber templates for the legs and still messed it up! Outdoor table build

Offcuts cost nothing and practice makes life much easier.

With the chock, I woudl remove it before you nail the others home, just to see if there is any play in the stained glass really, no other reason.

Dave

[BoeingFan]

Hi @EricL 

Re the timber screws, is it possible I could use some of my many leftover macsim stainless steel T25 star drive 10G-10 x 50mm screws, or would they be too soft? I still have the 'clever tool' they came with, or I could just use a standard drill bit? What size drill bit would you recommend? I can't find these decking screws on the Bunnings site anymore...

Macsim 17SSCBRX1050U

Thanks,
Jason

[JacobZ]

Hi Jason (@BoeingFan),

Yes, those screws would be perfectly acceptable for this application, you'd just want to make sure to predrill and apply pressure when driving them in, as you seem to be aware, stainless-steel screws can be a bit soft. 

The "Clever Tool" would be perfectly fine for predrilling, and it would add a nice countersink for the screw heads to sit in.

You could also use a standard drill, but with a separate countersink bit to achieve the same result. You want a drill bit that is roughly the same diameter as the shank, but smaller than the thread. This allows space for the screw to drive into the timber while still cutting in to get the holding forced. You'd have to compare the drill bit to the screw to be certain, but a 3mm drill bit is usually about right for pilot holes for decking screws. 

Let me know if you have any further questions.

Jacob

[BoeingFan]

Hi @JacobZ 

Thanks for your reply. Yep, I think I'm 'burnt' enough with those stainless steel screws to skip them, thinking about it more. I'm going to grab the Zenith 8 - 10x50mm timber screws (that's a very confusing name to me), because the width of the stained glass window frame is 30mm, so I hope 20mm into the hardwood will be sufficient to hold it so I can remove the chocks, and, for the new exterior frame I'll be screwing through 19mm hardwood, then cement sheet, then hardwood studs, so I think the 50mm will be a great choice. 

Cheers,

Jason