Which Vermiculite

[slowfood]

I wish to cast an insulated base over the concrete base using vermiculite, I see there are two grades, fine and pellets, Which is the better ( I am assuming Pellets would make a much stronger aggregate) Also where is the cheapest place to buy Vermiculite.
Also which grade would be better for the dome render (I assume fine would be easier to spread and finally what ratio, would it be the usual 5/1 mix. Thank you all

[DuncanM]

Hi Slowfood,

People use vermiculite for insulation, the reason it's good as an insulator is because of how light and how much air it traps. The smaller the size of the vermiculite the less air it traps, so you want to go for the larger stuff.

I have found that the cheapest place to buy it is at Jewsons using the forum discount. It works about to be about £10-£11 per 100 Litres.

I do not know from experience about the dome render, but I doubt you would want to include the vermiculite in your render. You'd want to insulate with a layer of vermiculite, smooth over the surfice and then render.

I used a 5/1 mix throughout, but you could use a weaker mix quite easily.

Some people have had trouble mixing vermiculite, I for one have not - I recommended soaking the vermiculite first before mixing it with cement rather then adding the water after the vermiculite and cement have been mixed.

Cheers,
Duncan

[slowfood]

Excellent, Thank you very much, Jewsons it is then...

[cannyfradock]

Slowfood......or sonomocast?

I've only ever come across one grade of vermiculite from the builders merchants. I always thought the pellets were perlite?

The guys on the FB forum generally go for the coarse vermiculite.....and swear by its strength. Many of our members have also gone down that route, but many others...including myself have used thermolite blocks in the place of vermecrete in the base construction. They work really well, are really light and you can cut them with a handsaw...and they're only about a quid each.

I've always used vermecrete on the dome on top of the thermal blanket layer....using the same method for mixing as Duncan.

If you are buying anything from Jewson, don't forget to mention the forum account number. More details here...

ukwoodfiredovenforum.proboards.com/index.cgi?board=membersdiscounts&action=display&thread=82

All the best with your build

Terry

[twobecks]

Hi Slowfood,

I mixed a vermecrete base last weekend, and can definitely recommend Duncan's presoaking of the vermiculite. Makes mixing a lot easier. I then laid firebricks over the top (to get the hearth floor height nice and uniform) while it was still wet.

One week on and it's cured well and I managed to get the dome in situ.

Good luck with your build!