How to fix cracked wood on sash windows?

Hi Bunning Brains Trust.

I have some sash windows (up and down motion) where there is a crack in the lower (fly screen) portion of the timber on the interior side. This can be seen on Image 1. Image 2 shows how the join between the two window sections there is a gap (compare to another window image 5).

Initially I thought a plate of some kind however as per image 3 it closes too snug for anything however thin to fit e.g. https://www.bunnings.com.au/carinya-100-x-100-x-25-x-1mm-galvanised-l-shape-make-a-bracket_p3960650.

Outside looks ok for the moment (image 4)

My initial thought is perhaps I squeeze some liquid nails of some kind into the crack / and gap to the glass section then clamp it as it dries (just enough of a gap between fly screen to get a small clamp in there)

Any thoughts on this approach and if viable what type of liquid nails there is a bewildering array and would presumably need something water soluble and relatively 'liquid' to jet in there - my initial thought was this as it seems to have high grip per m2-

https://www.bunnings.com.au/selleys-350g-heavy-duty-liquid-nails_p1210564

Thank You,

SamMacImage 1 Cracked sideImage 2 - other sideImage 3 - ClosedImage 4 OutsideImage 5 comparison window

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JacobZ

Hi @SamMac,

Being a timber-to-timber connection, Liquid Nails isn't your best option because you don't want any flexibility. PVA glue is a better option for this type of bond, and this Aquadhere PVA Wood Glue would be my choice.

I'd use a chisel to slightly open up the gap, then use a small craft brush to apply the glue inside the crack.

If you have a clamp that will work to hold the gap closed, then go right ahead with it. If not, you could always tap a wedge into the gap above the crack to force the crack closed while the glue dries.

Make sure to wipe away any excess glue that squeezes out while it is still wet.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

SamMac

Thanks @JacobZ for guidance on a more suitable product!

So to confirm the idea is,

a) use something to open up the gap (but not trying to scrape anything out) (bit thin for my chisel but I have some other tools from modelling hobby)

b) then 'paint' in the glue (I have some brushes from a modelling hobby that should do that easily),

c) then clamp it up to join both sides and keep them together and wipe off the excess that spills out.

Thanks again

JacobZ

That's it @SamMac.

There's no real need to remove anything because nothing has really moved to begin with. Timber is comprised of two main components, cellulose (fibres) and lignin (glue). When timber cracks like this, the lignin has basically let go, so the cellulose is no longer glued together, but it hasn't really shifted out of place. All you are doing is readding a substitute for the lignin and holding it in place while it sets.

Good luck and let me know how you go.

Jacob

SamMac

Update on how it went. Got the aquadhere as recommended.

First got all tools together and did a dry test to make sure i could pry it open enough to get a small get brush in.

Then went ahead with the actual 'painting' of the glue into the cracks

Went well, a bit fiddly to really push it in to the thinner sections, and made sure to have damp towel on hand to wipe up excess notably when clamping some squeezed out.

Then clamped it up as shown for 8 hours.

That was Saturday morning now Thursday afternoon and its still in place and set, while still visible no looseness along the crack at all!

Thanks for the tips @JacobZ

EricL

Hello @SamMac

Thank your very much for the update. The repairs are looking good.

Eric

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