Brush on sealant

[Philip Benson]

Hi all,

I'm getting close to holding up the while flag with this one so... HELP!   

My observatory has fibreglass base ring which is sitting on a hardwood surface (see pic). Ever since I installed this I have had a problem with water leakage through the base ring. I have tried silicone sealant but not matter how hard I try I always seem to miss a bit and the water seeps through.

There must be a brush on sealant that I can use which I can apply all the way round the base, both in and out so it seals any gaps for water to seep through. We even tried applying some primer and then flashing strip but it seems flashing strip does not adhere to hardwood very well. Can anyone recommend anything please?  

[Davey-T]

A non silicone based sealant is probably a better bet, something like this maybe, there are also similar proprietary products than can be applied to damp surfaces.

Dave

https://www.ebay.co.uk/itm/Coachman-caravan-motorhome-sealant-adhesive-290-Bostik-Simpson-ISR-70-03-sealer/381548324978?hash=item58d60d6872:g:b84AAOSwezVWxILt

[Craney]

I've used this on sheds and flat rooftops

https://www.screwfix.com/p/cementone-waterproofing-bituminous-paint-black-5ltr/82914

Very sticky, and astro-black.

 

[johninderby]

I’ve used this and it worked perfectly. Stays flexible so won’t crack and thick enough to seal fair sized cracks.

https://www.screwfix.com/p/thompsons-high-performance-roof-seal-black-2-5ltr/46708

Edited October 22, 2019 by johninderby

[Philip Benson]

Thanks guys you are giving me hope that I might finally solve this one!  Any more suggestions, keep them coming.

[banjaxed]

I recently fixed a leaking shed roof with a can of roofing felt adhesive from Homebase. It is an adhesive but it works very well as an sealant.

[Grumpy Spider]

Hi Philip, if you are still looking for a solution I can recommend:

https://www.toolstation.com/puraflex-40-high-modulus-pu-sealant-adhesive-300ml/p85566

2 concentric rings around area clamp/screw down but do not tighten all the way try to leave half a turn leave for 12/24 hours then tighten down. Only comes in black or white tho'

Been using this for a few years now on various boats to fit hatches, windows and deck fittings works a treat. if in the future you wish remove the ring  run a thin blade knife round it will come off.

I get it from the basildon branch if you are that way.

colin

[Bukko]

Hi Phillip,

Just stumbled on this thread, hopefully you have an answer to the sealing issue now.

Critical will be the problem of movement in the wooden floor, what seals today might probably be an issue later. The Scopedome instruction manual for the base ring quotes something like 1mm out on flatness. Are you sure the wood is stable enough for this?  Anyway, hopefully it will be OK.

One other thing from the picture, I can see the motor mount for the dome. The gear that meshes with the cog ring is pretty thick and I notice the power cables looks to be pretty close. Please make sure the wires are nowhere near the cog ring, as you REALLY don't want them to rub.

I recently built a 3m Scopedome, so if you want to chat, feel free to PM me.

Gordon.

[Swoop1]

I recently used flashing tape to seal a leaky flat roof. To get it to adhere to a rendered wall I used this bitumen primer- https://www.diy.com/departments/roof-pro-universal-bitumen-primer-0-75l/1932720_BQ.prd

It is as thin as light oil when fresh and dried very quickly. The flashing has adhered exceptionally well, even on dry, somewhat powdery painted render. I used an electric paint stripper gun to heat the flashing to soften the sticky side and then used a wallpaper edge roller to really compress the seal.

[Physopto]

Sikaflex 512 as used for caravan seals on roofs etc. It is UV stable and works. There is also Soudal FixAll sealant cheaper and works. Neither work on a wet surface! So make sure the surfaces are very dry before applying. 

Are you absolutely convinced the leak is actually coming from the bottom seal and not tracking from somewhere above? 

Best of luck. 

Derek

[Skipper Billy]

A bead of this stuff should cure the problem

https://www.travisperkins.co.uk/glazing-and-frame-sealants/c-tec-clear-sealant-ct1-tube-290ml/p/991099

Used to fix leaky boats etc

[timwetherell]

What about a two part epoxy? That can be brushed on, sticks like the proverbial to a blanket and unlike polyester resin, has a little give even when set which should suit a wooden floor?

[Skipper Billy]

32 minutes ago, timwetherell said:

What about a two part epoxy?

It would work but would need painting as epoxy is not UV stable - it will break down is sunshine (and its expensive!) 

[timwetherell]

7 minutes ago, Skipper Billy said:

It would work but would need painting as epoxy is not UV stable - it will break down is sunshine (and its expensive!) 

With the kind of summers we get, UV isn't likely to be a problem!  But, you could maybe mix it with a pigment such as childrens black powder paint or as you say, paint over it anywhere it's exposed to a lot of light. It's not really much more expensive that most sealants, it's about £20 for half a litre on ebay

[hughgilhespie]

I would recommend CT1 sealant. It is waterproof, UV resistant and it has held my observatory together for the last 5 years. It will even stick over previously applied silicone.

HTH, Hugh

[Paul M]

Are you trying to seal the base ring internally? The problem with that is weather will continue to drive water in from the outside and it'll be trapped there for eternity plus a few days.

Better to seal externally using flashing tape/band as mentioned above. I can't see the external construction but trying to get anything to make an impermeable seal with an exposed timber base is going to be difficult. 

Get a built up felt roofer to come and do a hot bitumen and felt job of the external timber  or even do it yourself with cold felt adhesive, then apply a lovely trim of flash band at the junction with the base ring. Simples!