# fill screw holes with tube mastic or sikaflex?



## nafricasurfer (Jan 22, 2014)

Hi all -

I'm now taking my own advice and just replacing the ancient screws down the side of the Euramobil.

Now that I have holes... I'd like to seal up those holes a bit when I add the new screws. Should I squirt in some mastic? Or should I squirt in some Sikaflex?

Thanks for any sort of advice or opinion
Matt


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## listerdiesel (Aug 3, 2012)

Either, Sikaflex will go harder and grip the screw.

Remember that Sikaflex 221 will go like a strong white rubber, it can be cut and trimmed with a sharp blade.

Peter


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## nafricasurfer (Jan 22, 2014)

I figured the mastic would squeeze in everywhere. 

I was wondering about sikaflex because their docs say a 2mm bread is ideal & inside a screw there is no 2mm bead.

However, I was thinking to start with the sika because if it doesn't work, then I could try the mastic over the sika. Sika over mastic probably would not be so great, I'm guessing. (does sika bond to mastic?)

For a mastic, I was planning to use the Unibond gutter sealant which is a butyl mastic. Unfortunately I don't have the time to get ahold of Carafax tube mastic.

Matt


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## nicholsong (May 26, 2009)

Matt

On boats we just use 221 and that is a harsher environment as when a boat is \'slamming into a head sea the vibrations are harder than on a pneumatic-tyred and sprung MH, and it is subject to salt water and, in Greece quite high temperature differences.

We use it under srew-on window frames and in screw holes. Just put enough in so that it squeezes out when tightening, let it go off for 48 hours, then trim off the residue with a hand-held Stanley knife and any thin residual residue on the surface can be wiped off with acetone on a cloth - by that time the Sikaflex seal will not be damaged.

Not sure gutter sealant would come in \'white\'

Geoff


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## nafricasurfer (Jan 22, 2014)

Hi Geoff -

It\'s good to hear about your actual experience using sikaflex to fill the holes.

I\'ve been to Greece & can\'t remember any big storms, but I\'m sure they do happen! 

My big question with Sika & screw holes is... what happens when the sikaflex breaks the bond? Say someone goes and removes a screw and breaks the seal. Can sikaflex bond to siklaflex? Could you just top up a bit more into the hole & reseal?

Also, do you think Sikaflex EBT would be OK to use too? I want to keep the last bit of my 221 for interior seals.


Thanks!
Matt


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## nicholsong (May 26, 2009)

nafricasurfer said:


> Hi Geoff -
> 
> It\'s good to hear about your actual experience using sikaflex to fill the holes.
> 
> ...


Matt

Apologies for this late reply, but I thought I had answered before but the post is not there for some reason.

There do not have to be storms in Greece - a Force 5 can create short choppy seas.

I would not put new Sikaflex onto old - I would always clean old out and clean surface with acetone before re-sealing.

I do not know Sikaflex EBT so cannot comment.

Geoff


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## nafricasurfer (Jan 22, 2014)

Hi Geoff -

Thanks for your note. Sikaflex EBT is the stuff they sell at screwfix. More easily sourced for me on a short timeframe so that's why I'm using it. Sounds pretty much like the same as 512 but just no UV protection from discolor.

Today I put a little sika on top of old sika around the screw holes. Hard to get old sikaflex out of the screwholes without putting a screw in & out and that would tear at the mastic.

Only 4 more screws to go in and I'm done with the job. Would have finished today but the sun ran out.

Cheers-
Matt


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