# rail seam reseal with mastic tape or sikaflex?



## nafricasurfer (Jan 22, 2014)

Hi all -

I am about to reseal the rail seams of my camper. Along the corners holding the two pieces of aluminum (wall to ceiling together).

Some of what I read suggests mastic tape. Other people use sikaflex.

I don't understand the merits of either. 

Some people say mastic tape is not good and leaks. Other caravan repair centers use it to seal the rails.

Thank you-
Matt


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## bigcats30 (Aug 13, 2012)

I'll keep this as simple as possible as you will get inundated with useless info.

Mastic is a sealant (putty type) that DOES NOT HOLD STUFF TOGETHER...ie you MUST use it with screws etc...it is very good (most roof lights etc are sealed by this stuff). 

Sikaflex is a bloody strong glue that also seals and once set is extremely hard to remove...you DO NOT NEED SCREWS when using this....however you could use screws with it.

That is the simple difference between them.


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## nafricasurfer (Jan 22, 2014)

Yes I have both here. Been using the Sikaflex to hold together the shower cabin. I've got some w4 mastic tape too.

I just don't know which is the best for sealing under the outer rails.

The rails have screws & the old material was a mastic type material. I suppose that should be enough reason to use mastic again.

I've read somewhere though that someone's mastic tape didn't seal well & they had leaks.

I've talked with two different caravan repair centers. One would use the mastic tape. Another would use a non setting mastic that you squeeze on with a tube. Talked also to a sort of motor home handyman who uses sikaflex for everything. but mostly installs solar panels.

Also there is mastic tape & then there is plain non setting mastic that you squeeze on with a tube. Any differences there?

Thanks!
Matt


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## nicholsong (May 26, 2009)

bigcats30 said:


> I'll keep this as simple as possible as you will get inundated with useless info.
> 
> Mastic is a sealant (putty type) that DOES NOT HOLD STUFF TOGETHER...ie you MUST use it with screws etc...it is very good (most roof lights etc are sealed by this stuff).
> 
> ...


There are many products from Sikaflex. Some are just mastics some are adhesive.

I use Sikaflex 221 on the boat as a sealant but it could not be used as an adhesive.

Which Sikaflex product do you use as an adhesive?

Geoff


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## listerdiesel (Aug 3, 2012)

221 works fine as an adhesive, Geoff, you just need to support the pieces while it cures, just like Araldite.

Peter


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## nicholsong (May 26, 2009)

listerdiesel said:


> 221 works fine as an adhesive, Geoff, you just need to support the pieces while it cures, just like Araldite.
> 
> Peter


Peter 
Maybe it is the ambient temperature - I am using it in Greece and two days later it will still be tacky. Sikaflex website specifies the temperature range for each product.

Geoff


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## listerdiesel (Aug 3, 2012)

I find that it goes off as far as a skin forming in a couple of hours, but normally allow 24hrs before handling and 48 for loading.

It cures with moisture from the air if I remember correctly.

Peter


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## nafricasurfer (Jan 22, 2014)

My Sikaflex is 221.

But I think I'm going to use W4 mastic tape under these seams. On top of that will be a strip of aluminum held down with screws.

Cheers
Matt


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## pomme1 (May 19, 2005)

Matt,

Make sure you use stainless screws.

Roger


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## nafricasurfer (Jan 22, 2014)

Hi Roger - 

Definitely that is the plan. I need to put some on order from screwfix if we can't source them from around here (Londonderry).


Which would you use to seal Roger... an adhesive sealant or a non setting butyl mastic?

Thanks!
Matt


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## pomme1 (May 19, 2005)

Matt,

I think I would be inclined to use a non-setting sealant in that area, although I am not certain that butyl-mastic is the right stuff. Others with greater knowledge may care to comment. 

Roger


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## bigcats30 (Aug 13, 2012)

I would go with the sealant.....just make sure you have enough.


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## nafricasurfer (Jan 22, 2014)

OK... I think I'm going with the W4. I'll see if I can get some quick to Londonderry!

Wondering about those stainless steel screws now though. I read that stainless steel and aluminum will react with each other?

Matt


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## pomme1 (May 19, 2005)

Matt,

Thinking about this, the advantage of the W4 is that it won't be squeezed out of the joint when you tighten the strip down.

Roger


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## nafricasurfer (Jan 22, 2014)

Hi Roger -

I think I'm going for the mastic. 

Now I'm just trying to decide which one. Some people use Caraflex IDL 99. Other people use the W4 mastic tape.

I suppose the W4 is for the convenience of not needing to flatten it out and being sure it is applied evenly. 

I think people like the Caraflex because it is good & is also cheaper.

Anyone have something to add here?

Matt


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## pomme1 (May 19, 2005)

Matt,

The point I was making earlier is that the W4 tape is probably better because it won't be squeezed out of the joint when you tighten the strip down. With gun applied mastic, however, you cannot be sure that once the strip is tightened down that you have a consistent thickness, or indeed any thickness, of sealant under the strip. 

I don't know if stainless steel reacts any differently from mild steel when in contact with aluminium. I would have thought it less likely to react as it has some aluminium content. I guess the only other alternative would be brass screws, but I've never seen those used.

The above is just my view, but I'm certain that there are others better qualified than me who may respond shortly.

Roger


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## nafricasurfer (Jan 22, 2014)

I spied a sika butyl tape Screwfix has... wondering if this will do as a butyl mastic tape? I'd need a way to cut it into three (100mm wide & I want 33mm)

I already bought some of this: 
http://www.caravanaccessorysho...m-x-5m/572

and wonder if i could substitute with this: 
http://www.screwfix.com/p/sika...-10m/38892

It's much cheaper.

Matt


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