Sika 522/221 or OB1?

[Paul Gosbee]

Hi Fellow Moho Owners

Had a major ingress of water from around the window seals of my moho. The bead of Sika 221 had shrunk in the weeks of heat a while back which I hadn't noticed. I have removed one window, removed all the old putty/mastic and am now ready to put it back. I am using W4 mastic strip as the main water stopping sealant but want to use a bead of mastic on the outer edge of the window flange as a first line of defence so to speak. Has anyone used OB1 (forget the Star Wars jokes ie 'This is not the sealant you are looking for!' etc etc etc!) as I don't want sealant failure and have to start all over again.

On removal of the window, I found Seitz had put a rubber gasket in a groove around the inside of the flange. This had perished over 20 years and of course it's no longer available nor is there any suitable Seitz replacement (typical!!!) Judging by the price of new seals for S4/S5windows (£60 !) I would have to go to the bank for a loan anyway!! I have some very similar window gasket on order from EBay at £1.50 per metre which, if it fits, will be a great find!! Eat your heart out Seitz, Dometic, Thetford, Electrolux, Ultrastore or whoever you are! I will update this post on the outcome so anyone else facing the same issue with window gaskets can benefit perhaps. Please let me know any ideas or experience with OB1 v Sika 221/522.
Thanks
Paul

 

[welshcake lady]

Hi I've used sika 522 brilliant stuff
it supercedes sikia 512 which was also great.

 

[Richard n Ann]

I've heard puraflex 40 PU is as good and only £6.99 at Toolstation

 

[Paul Gosbee]

Thank you both for your replies. Most helpful.
Pail

 

[Paul Gosbee]

Sorry should be Paul not Pail!!

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[PeterCarole29]

Hi I bought some OB1 the other day as I couldn’t get sika quick enough. Looking at the spec it says uv resistant where as it didn’t on the sika. I have used both and in the passed after use have noticed how much the sika shrinks in the nossle when it drys but not in the OB1 . I found OB1 finnishes with a shine and is more flexible.
I was pleased and will use it again

 

[Paul Gosbee]

Hi Peter

Thats very useful to know. Any thoughts on removing it. I used white spirit to shift the old Sika 221?
Cheers
Paul

 

[PeterCarole29]

Hi I have had to remove old OB1
Only wash it off hands and wipe edges when I fitted my windows
I used white spirits
I have often used the earlier suggestion of puraflex from toolstation it does the job but only downside I found as it finishes Matt unless you paint it it attracts the dirt
But to be honest haven’t used OB1
Long enough to know if that does the same but the Finnish is smother and has a shine so maybe not

 

[Raul]

Have used OB1 no issues However, CT1 it’s still superior in my book. I sealed a leaking pool outlet shroud with the water in. Yes it works under water. The pool never leaked since I fixed it, almost 2 years ago. I just did a stove pipe seal trough metal roofing with puraflex also good.

 

[Paul Gosbee]

Thanks Raul for that, very helpful.

Paul

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[Paul Gosbee]

Thanks Peter.

 

[Paul Gosbee]

Update on sealing Seitz windows. After cleaning off old putty sealant and removing perished window gasket (that chose to weld itself into the gasket groove!!) I have now refitted the windows using some gasket I got form ebay at £1.50 per metre. It has the code R6549X. As you will see from the picture attached it has a 3.4mm fixing 'arrow' which fits snuggly in the 3mm groove on the inside of the window flange. After tightening up the inside frame carefully by applying the same torque to all the screws (much in the same way you tighten a cylinder head!) I tested the unit with a hosepipe and hey no leaks. I then applied an additional bead of OB1 sealant around the outside to make sure as a belt and braces thing. Trying to get the OEM gasket is a no go but his is a cheap and effective way of resolving the issue. You also you don't need to apply any sealant on the inside of the flange (W4 etc) as the gasket is very substantial. Hope this helps anyone else in the same boat. Happy to answer any questions as far as I can. Given up using Silka 522 as it is so messy to try and smooth out. OB1 is a doddle - 'This is the sealant you are looking for!' hee hee

 

[Paul Gosbee]

Oh I forgot to mention, all surfaces on the window flange and the area around the window opening on the moho have to scrupulously clean. I used white spirit which removes old sealant and the like. Doing a final wipe over with meths makes doubly sure.