How to fix the gap between outdoor wall render and window frame?

[mocca28]

Hi Team - need your expert input to close the gap as shown in the photos. We tried using standard selleys clear

 

silicone but it didn’t stick to the wall render at all. We suspected that this gap has caused rain water to sip into the house and causing the timber floor to warp. Your expert opinion will be greatly appreciated. -Han

 

[EricL]

Hello @mocca28 

Welcome to the Bunnings Workshop community. It's fabulous to have you join us, and thanks for sharing your question about filling the gap between your window frame and the wall.

Looking at the photos you posted, it appears that there is a seal already in place. Is this the old seal and are planning on removing it? If you are, I propose using Selleys 430g White No More Gaps Exterior Gap Filler.

To ensure that the gap filler anchors well, I suggest washing the rendered surface with water and detergent to make sure that it is free of dust and debris. Once the area is totally dry you can then apply the gap filler.

Here is a handy step-by-step guide: Selleys No More Gaps

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

Eric

[mocca28]

Hi Eric - thanks for the reply. Yes, there is an existing seal (not sure what it is as it feels hard unlike rubber seal). The gap between the wall render/concrete and the window frame is about 1-3mm at various point and we are concerned that this is the source of water leaks. 

for the recommended seal, does it work with render like mine? When we applied the standard Selleys silicone, the render kept shedding its sand grain and nothings stayed. We cant wash or scrub the surface too as it will crumble. 

1) will the selleys recommended work well with this surface?
2) Do we need to remove the existing gap filler (that feels like a concrete based)? 

3) is there a better way to close the 1-3mm gap?

Regards. 

[EricL]

Hi @mocca28 

Thanks for sharing that extra information about your render. Have you tested to see if the rendered edge can be cleaned with a brush? If it continues to deteriorate, I'm afraid this issue will need to be addressed first before you're able to seal the window frame.

Any sealer placed will simply come off the loose substrate of the wall. I propose either rendering it yourself or engaging the services of a trade's person to re-render just the internal edge of your window frame. Once the render cures you can then seal it with silicone.

In regards to the old seal, it will need to removed so that you have a fresh base to put the silicone on.

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

Eric

[mocca28]

Hi Eric - we might try to fix the render around the windows (there are 7 in total…) first as you have suggested. What would be the recommended materials and tool to use to fix the render?

rgds. 

[JacobZ]

Hi @mocca28,

You should start by cleaning the areas thoroughly to remove any loose materials that will prevent good adhesion. I propose using soapy water and a good firm bristled brush such as Sabco Bamboo All Purpose Heavy Duty Scrub.

Once sufficiently clean, you should tape off the aluminium using painter's tape to prevent any damage to the window frame. You should then apply some Dunlop 4L Premix Render Joint And Patch to the gap using a Kango 150mm Joint Knife in conjunction with a pointing trowel such as Kango 10mm Tuck Pointer.

If you find once removing the sealant that there is a large cavity beneath that the render could fall through upon application, it will help to add Moroday 15mm x 5m White Gap Filler Rod to fill the gap before rendering over the top. Once the render has dried, remove the painters tape and brush down to clear away any loose material and give a nice finish.

To create the perfect seal, you should then add a bead of Sika 300ml 11FC Plus Polyurethane Adhesive Sealant in a suitable colour to cover any small holes that may be present right up against the aluminium frame.

Have a look at these helpful D.I.Y articles for a bit of guidance on the rendering process -

How To Render 

How To Render Corners 

How To Apply a Top Coat To Render

Please reach out if you have any other questions or require some more guidance.

Jacob