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How to add sub-frame to window for secondary glazing?

lm4

Hi all,

I am hoping to add some secondary glazing to a few of our windows with 3mm acrylic panels and magnetic tape, similar to the below link:

https://www.omegabuild.com/resource/how-to-fit-a-secondary-glazing-panel-with-magnetic-tape

To fix the panels into the window frames, I'll need to add some internal structure as the current frame doesn't have a sufficient "lip" for me to attach the magnetic tape and panels to (see below).

To add the internal frame, I'm considering using 18x18 moulding (either Pine or PermaTimber) cut to size and installed into the existing frame but not quite sure how best to attach this? Would timber glue be sufficient, noting I'll need to push on the magnetic tape adhesive pretty firmly, or should I use nails with timber glue just at the corners?

Any other tips on how to make this internal framing and make sure it fits well within the existing frame would be appreciated.

Thanks!

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EricL

Hello @lm4

Instead of nails, I propose using https://www.bunnings.com.au/titan-6g-x-30mm-ph2-plasterboard-screw-40-pack_p0912046 . I suggest drilling pilot holes in the pine moulding every 300mm to 400mm depending on the length of the window. This will prevent the pine moulding from splitting apart. If you are keen on putting adhesive, I suggest looking at https://www.bunnings.com.au/selleys-250g-liquid-nails-clear-construction-adhesive_p1232420 . I recommend a light bead on the pine trim so that it does not overflow past its width. My best advice is to do a dry fit to make sure everything lines up before fixing the trim in permanently.

Let me call on our experienced members @Nailbag, @Dave-1 and @Noyade for their recommendations.

Please remember to wear personal protection such as gloves and goggles while working on your project.

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

Eric

Dave-1

Good Morning @lm4

I have considered that type of idea before, tho I dont have a high degree of confidence in the magnetic strip holding the weight of the panel. Or that the the panel wont wobble over a reasonable span. (like a wobble board type deal) It will be interesting to find out if you go ahead with the idea :) )

Instead of adding beading to attach the magnetic strip to, why not use the window trim itself? Its already existing and no extra screws are needed. The magnetic strip should hold its weight (according to the video) Worst case you may need a bottom trim to support the weight and then the magnetic strip can sit on the top and sides to hold it in place (Beware of the wobble with say closing doors)

Dave

R4addZ

Hi @lm4

The only problem with pine moulding is that you will need to paint it. You would have needed to do something like this even if the lip had been big enough due to the lock being in the way. Might I suggest using aluminium angle instead of the moulding as it will match in with the frame and so not need painting like this

https://www.bunnings.com.au/metal-mate-20-x-12-x-1-4mm-3m-aluminium-unequal-angle-silver_p1079496

There is one that is 40 x 40mm but it is more expensive.

I wouldn't worry about wobble either as the air trapped between the window and the panel will have a dampening effect.

lm4

Hi all,

Thanks a lot for the advice! I’ll aim to do use some antique white pine with the plasterboard screws and some adhesive.

Unfortunately the existing lip in our windows is very narrow (<5 mm) so not confident the tape would hold. It’s also a bit uneven so I think it would be better to make a new wider surface to attach to.

@EricL, any suggestions on how to ensure a nice snug fit for the new structure? Is cutting the corners at 45 deg a better approach than just having straight sections for example? I’ll definitely be doing a dry fit first to make sure it all sits well before attaching.

@Dave-1 if it works I’ll update this post! I’m pretty confident the magnetic tape I’ve bought should hold but time will tell

EricL

Hello @lm4

I propose doing straight sections as installation is much simpler and straightforward. However, if you are keen to try a 45degree join, I strongly advise triple checking your measurements and to use an https://www.bunnings.com.au/empire-300mm-combination-square_p5667081 to mark your cutting guide.

If you need further assistance, please let us know.

Eric

Dave-1

Afternoon @lm4

The blue line is where I was thinking of fixing the magnetic strips. And if needed a timber trim across the side of the base to take the weight of the sheet of

3mm acrylic panels.

Dave

lm4

Thanks @EricL I will do in straight sections for simplicity. Any tips on closing up small gaps between the sections if I don't get it exact?

@Dave-1 thanks I see what you mean now! I was assuming the much smaller groove at the edge of the frame. This would work for this window, however for others we have some roller blinds mounted which I'd like to still use so the acrylic will need to fit inbetween the glass and these blinds! I will see how this goes and update you.

Cheers

EricL

Hello @lm4

I suggest using https://www.bunnings.com.au/parfix-500g-ready-to-use-multipurpose-filler-500g_p1210321 to fill in any gaps and get that flawless finish you are after. I recommend using a https://www.bunnings.com.au/paint-partner-cork-sanding-block-2-pack_p0328975 in order to get a flat level finish.

Eric

lm4

Hi @EricL

Sorry one last question - any things to keep in mind if I use PermaTimber instead of pine? Considering using this as it’s already painted:

https://www.bunnings.com.au/permatimber-18-x-18mm-2-7m-antique-white-pvc-composite-dar_p0497595

thanks!

EricL

Hello @lm4

The https://www.bunnings.com.au/permatimber-18-x-18mm-2-7m-antique-white-pvc-composite-dar_p0497595 should work just as well. My best advice is to make sure that the pilot holes you drill are big enough to accommodate the screws I've suggested. Please note that the PVC composite behaves differently to pine moulding. I recommend using https://www.bunnings.com.au/selleys-150g-white-no-more-gaps-multipurpose-gap-filler-tube_p0147102 to fill the gaps between the composite pieces.

Eric

MitchellMc

Hi @lm4,

There were some really interesting ideas shared throughout this discussion, so I’d be keen to hear which direction you ended up taking with the secondary glazing.

Did you end up going ahead with the PermaTimber framing and magnetic acrylic panels? I’ll be interested to hear how effective it is, once you’ve had some time with it installed.

If the project is still in progress or you’ve hit any roadblocks along the way, please feel free to jump back in and we can help further.

Mitchell

lm4

Hi @MitchellMc

Thanks for the prompt! I completed the acrylic secondary glazing last weekend and am really happy with the results. We ended up using 18x18mm Pine moulding instead of PermaTimber as that was what was available. I drilled pilot holes and applied wood glue as suggested by @EricL before fitting to the top/bottom of the window frame and then re-measuring for the sides and doing the same. Had to clamp the corners for a little bit for the glue to set, and then patched up any gaps with some filler.

For the acrylic itself, I fixed both the A/B sides of the magnetic tape to the acrylic panels first (i.e: acrylic → adhesive → magnetic A side → magnetic B side → adhesive (keep adhesive tape on the B side)) and then tacked opposing corners of the "B" side into the internal pine frame before removing the rest of the adhesive protection. Then took the panels off and allowed the adhesive of the B magnetic tape to fully stick before putting the acrylic up the next day.

If I was making more, I'd definitely do the following:

Order smaller acrylic panels (10-15 mm smaller than the frame). I ordered panels only 5 mm smaller and it was a bit difficult to fit into the gap with clearance for my fingers.
Fix the pine with screws at more points along the length, and closer to the corners to minimise the gaps to patch up.

The magnetic tape I used was from AMF Magnetics: https://magnet.com.au/products/magnafix-12-5mm-x-1-6-mm-30m-roll-w-tesa-4965-adhesive-part-b and https://magnet.com.au/products/magnafix-12-5mm-x-1-6-mm-30m-roll-w-tesa-4965-adhesive-part-a , apparently the Tesa one works better than other brands (according to the acrylic place I ordered my panels from).

EricL

Hello @lm4

Thank you so much for sharing that update. The timber trims look fantastic, and your installation looks very well done. That double glazing should help with temperature control and reduce the noise coming through your windows.

Eric

Dave-1

Good Evening @lm4

Looks good :) Would love to hear back after winter is over and see how well it worked. Even to the point of placing one of those Ashley Plastic Indoor Thermometers inside and outside and chart the temp :) Bit geeky I know but I think it would be interesting.

Dave

MitchellMc

Hi @lm4,

Great to hear the project turned out so well, and many thanks for coming back to share such a detailed update. It sounds like you put a lot of thought into the installation process, and your method will no doubt help others looking to tackle secondary glazing themselves.

Using the 18x18mm pine moulding sounds like a very practical alternative, and your step-by-step approach to fitting the frame and magnetic strips is excellent.

Really appreciate you taking the time to document the process and provide feedback on what you’d do differently next time. I’m sure other community members considering secondary glazing will find your experience extremely useful.

Mitchell