My UK build is out of the ground!

[Bookemdanno]

Re: My UK build is out of the ground!

Cheers Bookemdanno,

So with the two coat, is that using the k rend base coat they make before the final k rend finish?
With the silicone in the k rend, I take it you don't add an integral waterproofer?
Also what scratch coat mix did you use? 4:1 plastering sand-cement?
I intend on the scarified finish myself.
I also take your advice on the heartbreaks. Would that also be needed in my 'vault' area between the brickwork and render? Bearing in mind I have built a heartbreak out of insulation brick in the hearth between the oven and vault, and also between the oven arch and the vault arch.
It would be interesting to know how hot the vault area and chimney gets with the get breaks installed.

Many thanks

Allan

Hi Allan,

I didn't use basecoat, just two passes of topcoat to give about 20-30mm overall thickness. For your oven, i think i'd be tempted to use the basecoat and topcoat system, so that it finishes up with a thicker shell to your oven. However, in my research into K-rend, you can appply the topcoat over normal sand and cement render if you want to. You'll probably just negate the breathability of the system though.

Only add water to the render mix, everything needed is added. 4-5ltrs per 25kg bag, and mix well. I used a large bucket and drill mounted plaster whisk. One initial mix, leave it for a couple of minutes and then a second mix before use. It only has around 30-45minutes workable time, so have everything all ready before mixing and getting mucky!

I used a single walled flue for my oven, but changed it after there were definite heat/expansion related cracks eminating from it. The single walled flue gets barsteward hot!

Flue length...there will be optimum dimensions, but go with what looks best and you can get hold of easily. Cob ovens that have no real chimney work fine, along with commercial ovens with extremely long flue systems.
For a 42" oven, 8" flue is just fine. However if you want to use twin wall, then O.D is going to be 10" minimum. Just remember to allow for a heatbreak between any render and the flue, whatever you use.

Winters closing in fast! Quite a frost this morning in East Anglia!
Good Luck.

[vincentvega_uk]

Re: My UK build is out of the ground!

Hi Allan,

I didn't use basecoat, just two passes of topcoat to give about 20-30mm overall thickness. For your oven, i think i'd be tempted to use the basecoat and topcoat system, so that it finishes up with a thicker shell to your oven. However, in my research into K-rend, you can appply the topcoat over normal sand and cement render if you want to. You'll probably just negate the breathability of the system though.

Only add water to the render mix, everything needed is added. 4-5ltrs per 25kg bag, and mix well. I used a large bucket and drill mounted plaster whisk. One initial mix, leave it for a couple of minutes and then a second mix before use. It only has around 30-45minutes workable time, so have everything all ready before mixing and getting mucky!

I used a single walled flue for my oven, but changed it after there were definite heat/expansion related cracks eminating from it. The single walled flue gets barsteward hot!

Flue length...there will be optimum dimensions, but go with what looks best and you can get hold of easily. Cob ovens that have no real chimney work fine, along with commercial ovens with extremely long flue systems.
For a 42" oven, 8" flue is just fine. However if you want to use twin wall, then O.D is going to be 10" minimum. Just remember to allow for a heatbreak between any render and the flue, whatever you use.

Winters closing in fast! Quite a frost this morning in East Anglia!
Good Luck.

Thanks again for the advice.
I have opted not to go with twin wall due to the price. I will make sure I get some insulation between my flue and the render!
I too have read that a lot of people are using a sand/cement base coat for the k rend. I think for what I need I will stick with the K rend base itself.

Got my landing area and outer decorative arch in this week, need to now just set some bullnose bricks to tidy up the front of the landing down to my hearth, fire blanket everything up, fix the flue, ( im thinking of getting some sort of anchor plate made up to accept the bottom of the flue), then render/stucco.
Im going to tile whats left of my hearth around the oven in red quarry tiles I think.

When I get to the stage of curing my oven, can this be done once all the final render/stucco is complete or do I need to cure before this go's on?

Cheers

Allan

[brickie in oz]

Re: My UK build is out of the ground!

Whoah, nice arch....

[david s]

Re: My UK build is out of the ground!

I like to cure before doing the outer render. It gives the water a chance to escape more easily.
Ditto on the arch comment, very Roman.

[vincentvega_uk]

Re: My UK build is out of the ground!

Thanks guys.
I think I may need to cure first anyway. The cold weather is starting to set in here in the uk, and im not going to risk doing the render/stucco if I don't need to.

Anyway, got my brickwork complete, and tiled the hearth in some nice inch thick reclaimed quarry tiles.
Got 75mm on blanket on also, so Im going to omit the vermicrete.

Any advice/comments as always is welcomed.

Thanks

Allan