External window silicone gaps

Skipsteer · 7 Dec 2020

I've noticed some fairly big gaps in the silicone above a couple of our external windows.

I was just wondering if we might be better trying to use something other than silicone to cover this?

I'm thinking if we re-silicone, due to the size of gaps if might just break away again.

See attached photo.

Any suggestions or advice on this would be appreciated.

diy_fun_uk · 7 Dec 2020

tbh although difficult to gauge 100% from the pic, the gap doesn't look overly excessive. It's failed partly because the original bead wasn't quite wide enough for the gap, some shrinkage etc. I'd make good bits of crumbling concrete as can be seen in the pic, then would use this or equivalent:

Dow Corning Dowsil 796 LM Frame Silicone Sealant - Brilliant White (sealantsandtoolsdirect.co.uk)

Ensure you cut enough (but not too much!) off the nozzle to give a slightly larger bead than originally applied.

Notch7 · 7 Dec 2020

It might look neater to pull out existing silicone, put in new and trim over to hide.

Exposed silicone never looks great IMO

diy_fun_uk · 7 Dec 2020

Notch7 said:
It might look neater to pull out existing silicone, put in new and trim over to hide.

Exposed silicone never looks great IMO

I don't necessarily disagree, although I tend to reserve trim for larger gaps as trim can make the surface look slightly busy/cluttered. I think sealant looks fine ... if applied and finished properly

crank39 · 7 Dec 2020

I would pull off the old silicone, then either fill with a small bead of foam or seal it with silicone then slide a bit of 45mm trim in the gap and then seal with a thinner bead and also hiding the underside of the mortar/catnic killing 2 birds with one stone

Skipsteer · 7 Dec 2020

Thanks for all the suggestions.

Just to check I've understood correctly.

Could I use expanding foam instead of silicone and then cover with a trim?

It's colder than the min 5C recommended for applying silicone so that might be a good idea to avoid having to wait until it gets warmer.

In terms of a trim, where should this cover, just over the old slicone or completely covering the whole underside concrete section?

Any links or recommendations to appropriate trim options would be really helpful?

And also what's the best way to secure the trim?

Many thanks

diy_fun_uk · 7 Dec 2020

You have two basic trim options. Either like this, where you apply a thin section of trim to the flat edge of the window:

Or like this where you apply a deeper section of trim to the concrete underside (except yours would cover most/all of the concrete):

Lots of places sell it e.g.

White uPVC Trims | suppliers of uPVC Window Trims (directplastics.com)

Any type of good grab it type adhesive (suitable for exterior use and adhering plastic to concrete) will do the trick.

Harry Bloomfield · 7 Dec 2020

diy_fun_uk said:
Lots of places sell it e.g.

White uPVC Trims | suppliers of uPVC Window Trims (directplastics.com)

Any type of good grab it type adhesive (suitable for exterior use and adhering plastic to concrete) will do the trick.

Delivery will be expensive, despite the items being cheap - you might be able to collect, if there is a local Eurocell to where you live.

Skipsteer · 7 Dec 2020

Do you think I'd need to fill those gaps at all if I just cover with the trim?

Don't fancy spending too much time up on the ladders if I can avoid it. I know how long it can take to remove silicone at the best of times at ground level!

Or possible just fill those silicone gaps with expanding foam which is quick to do?

With the expanding foam should I only be using a small amount to cover the seal area?

Thanks again for your help with this

diy_fun_uk · 7 Dec 2020

In my opinion, these are your options and tbh any will be better than current situation.

1. Go with basic sealant out > sealant in as per my original suggestion. If you apply it correctly it will look fine and will do the job. No need to fill gap prior to assuming your bead is large enough.
2. Go with thin trim as per my first pic. It's easy enough when up there to run sealant into the gap before applying the trim. You should then run small bead of sealant around the trim to hide any slightly messy edges and aid draft-proofing.
3. Go with deeper trim as per my second pic and Cranks suggestion. Again, if going to that bother it's easy enough to fill the gap prior to adhering the trim. Again seal edges to hide any rough bits and aid draft-proofing.

Don't bother with expanding foam, size of gap doesn't merit it.

p.s. If you're slightly apprehensive working up the ladder, you might be better sticking with option 1 for quickness and easiness, just a thought.

p.p.s. If your other first floor windows have the concrete exposed but you don't intend to do anything with them, you might be better just doing option 1 so things look consistent across all the windows, again just a thought.

Skipsteer · 7 Dec 2020

Thanks for going through the different options. All makes sense.

I was just a bit apprehensive of spending too long up the ladders trying to remove silicone before applying a new bead. It took me ages to remove silicone from the shower tray recently, but hopefully it's easier to remove above the window like this.

Probably don't need to worry as much about making sure all the old silicone is 100% removed as well.

The other thing is the weather this now. It says on the silicone tube only apply above 5C, but not sure if it would make a big difference if it was say 1-3C.

diy_fun_uk · 8 Dec 2020

As long as you remove what you reasonably can it'll be fine. Just make sure your new bead is large enough to get good adhesion to both the window and concrete. You can apply in colder temps but things like flow and surface adherence can be issues. I'd say wait for a slightly milder day, ensure the surfaces are dry etc and go for it, but don't apply when the snow's falling

Oh yeah and with no disrespect, safety first. If you're not fancying the job, get a man in

Skipsteer · 8 Dec 2020

Thanks very much for all your suggestions and advice

I'll give it a go and if it feels too dodgy up the ladders get someone else in to do it

Should I just use a standard file to smooth down that lump of cement? I'm guessing that shouldn't cause any damage.

diy_fun_uk · 8 Dec 2020

Skipsteer said:
Thanks very much for all your suggestions and advice

I'll give it a go and if it feels too dodgy up the ladders get someone else in to do it

Should I just use a standard file to smooth down that lump of cement? I'm guessing that shouldn't cause any damage.

Not 100% sure what you mean by this. If you're intending to cover the concrete fully with trim and there are some bumps, then a standard rasp file will do the job. However if the bumps are small, remember those discrepancies would likely be accommodated for by the adhesive. If you're simply thinking of tidying the concrete up whilst you're up there, if you're just doing a new bead of silicon with no trim, then I'd just leave the concrete as is. First floor, no one's seeing it in close up

Skipsteer · 8 Dec 2020

Good point, no one will really notice it anyway and saves me some extra work

Thanks

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

External window silicone gaps

Skipsteer

Attachments

diy_fun_uk

Notch7

diy_fun_uk

crank39

Skipsteer

diy_fun_uk

Harry Bloomfield

Skipsteer

diy_fun_uk

Skipsteer

diy_fun_uk

Skipsteer

diy_fun_uk

Skipsteer

DIYnot Local

Similar threads