Sealing cut out in worktop for a gas hob

[Designerman]

I’ve cut a hole in my kitchen worktop to receive a gas hob and I thought that it would be a good idea to seal the fibers. I have use mastic sealant and smeared it along the cut edge. It looks fine but a colleague of mine seems to think that the heat could cause a problem with the sealant. Does anyone have any advice on this? The hob manufacturer does say not to use sealant between the hob and worktop but I assumed this is because it makes it difficult to remove the hob. It is a gas on glass Bosch hob.

 

[Scrit]

I'd certainly seal the worktop edges with something as any spillages are likely to cause the worktop to blow over time. Heat produced by a hob tends to rise in the main, so I can't see something like silicone being a problem, especially as every gas hob I've ever seen seems to have a steel shield around its innards. The main thing is to seal the underside of the hob (i.e. the "joint" between the hob and the worktop) using the manufacturer's foam tape kit - use silicone there and it becomes very difficult to ever get the hob out without risking scratching or worse still breakage if the hob is glass.

Scrit

 

[Deluks]

You can get a blu-tack type stuff specifically for this purpose. I've no idea what it's called or where to get it from though, sorry

 

[Bamber gaspipe]

Yacht varnish on exposed bits,loads of coats.....& you can buy different coloured heat resistant mastic around edges...

 

[Scrit]

Yacht varnish on exposed bits,loads of coats.....& you can buy different coloured heat resistant mastic around edges...

Yes, but yacht varnish never truly dries and remains slightly tacky - so in a kitchen it becomes a crud magnet - and most kitchen fitters simply won't have the time to put 6 coats on

Scrit

 

[Bamber gaspipe]

Fair enough...I made that up because I was bored....

 

[Diyisfun]

You can bed the hob in using 'plumbers mait', I did check with manufacture re temperature.
I required a flexible seal as the hob is on ceramic tiles.

 

[Designerman]

Thanks for the replies. My gut feeling was to seal it even though the instructions that come with the worktop (Ikea) only mention using foil tape – I’ll use that as well. I’ve seen on this site and other sites various things mentioned including varnish, PVA and special sealants. But I had the sealant handy and Ikea recommend spreading sealant along the edges of the sink cutout (for obvious reasons) so I thought it would be OK for the hob. But I mentioned this to a colleague and he then got me worrying. But since then I’ve checked the text on the silicone tube and it says that it can withstand heat to 180 degrees centigrade. The hob is above the oven but I can’t believe the void between the oven and hob will get this hot! You could cook at that temperature. The sealant that I’ve used won’t actually touch the hob – I’ve only done the cut edge. There is an additional insert with the hob instructions that says don’t use sealant under the rim of the hob and I guessed that this was so that it would be easier to remove the hob in future. The hob has a pre-fixed foam seal but I’m dubious about how effective this will be against water so was keen to seal the cut edge.

Well the silicone sealant went on a treat - I used latex gloves and spread it with my fingers – within a few hours it dried to thick rubber - so much easier than waiting for varnish to dry.

I’ll crank up the oven and hob and if it doesn’t all melt and drip into the electrics of the oven then I’ll be happy.

 

[Agile]

I dont fit kitchens or hobs altough I can connect then to the gas.

ll the hobs I see come with either a black or light blue stuff like bluetack for sealing or a foam plastic strip.

This will seal the joint against water ingress and mean there is no requirement for sealing the cut wood. If anyone wanted to seal it then yacht varnish sounds the best material but any oil paint would do.

I have ocasionally used neutral cure silicone to reseal the top surface to the hob. The one I use is a neutral cure industrial material designed for electronics use so I dont know how different it is from the ordinary silicone.

Tony

 

[Designerman]

Hi Tony,

The gas hob has a five year guarantee and the instructions are quite specific about not using any kind if sealant around the rim – so I don’t want to do anything to invalidate the guarantee. The hob has a foam strip fitted but I think there is always a chance of liquid getting under it – particularly if something boils over because the glass surface of the hob is completely flat with no lip around it to hold in any spillage. What concerns me is if the worktop fibres get wet the first I’ll know about it is when the thing starts to swell – which will be too late. And I guess the worktop manufacturer would say their guarantee isn’t valid because the hob should have been sealed with sealant . But I’m pleasantly surprised that the silicone can withstand 180 degrees – should be ok I think.

 

[Agile]

I did say that I used an industrial material ! Usually generic name of RTV. It may be a lot better than cheap domestic stuff.

Here's a description!

ASI 502
Industrial Silicone Sealant/Adhesive

DESCRIPTION

""""ASI 502 Industrial Silicone Sealant’ Adhesive is a one-part, moisture-curing RTV (room temperature vulcanizing) silicone that cures to a strong, silicone rubber that maintains long-term durability and flexibility. ASI 502 is a non-slump sealant and can be applied to vertical or overhead surfaces without flowing or sagging.

Because ASI 502 is a 100% silicone sealant, it has excellent resistance to weathering including ozone, ultra-violet radiation, freeze-thaw conditions and airborne chemicals.

Fully cured, ASI 502 has excellent adhesion to glass, metal, porcelain, ceramic, wood, most plastics and many other nonporous substrates.
ASI 502 can be applied to surface temperatures from -18°C to +50°C (0°F to +120°F) and after curing, withstands constant operating temperatures from -57° to +233 ° C (-70° F to 450°F). """""

I only work with the best products!

Tony