Hearth / fireplace question

[guy84]

Just as an update.

I got the fire up and running over the weekend, had a small fire first then a big one with airvents open running at max power and measured the heat of the wall with a thermometer. As suspected it was alot higher than the crucial 49degC.

Do you think taking the plaster board down and then rendering the area is a beter option or should i put in a cement board on?

I am inclinted to go for cement board as i'm not great at rendering.

If i go for the cement board how should i fix it to the wall, what adhesive is best?

Also can cement board be skimmed relativly easlly with the vitcas heat proof plaster?

Thanks

 

[Richard C]

Just as an update.
Do you think taking the plaster board down and then rendering the area is a beter option or should i put in a cement board on?

You could just wait & see what happens but I wouldn’t expect it to last more than a couple of months if my experience was anything to go by. What happened to the fire surround idea? Personally, I would use sand/cement/lime render, the lime being an important ingredient, & skim over that with the Vitcas.

By cement board do you mean Supalux? The board you use must be capable of withstanding the heat & be suitable for use as a boiler backing board; not all cement boards may be suitable. I would not advise sticking it over the top of what you already have, the PB has to come down. Neither should you rely on adhesive to hold it up there, it will most likely fail; mechanical fixings are essential IMO but follow the manufacturers recommendations for installation.

Most cement boards will accept plaster with the correct preparation; Supalux can be skimmed by sealing 5:1 PVA 24 hours before & then applying a PVA bonding coat 3:1 & skimming while tacky. I would advise that whoever does your plastering understands what they are doing; Vitcas is expensive stuff & has to be mixed using a mechanical paddle, you don’t really want someone who’s inexperienced getting it wrong.

 

[guy84]

Ok thanks richard,

Obviously it would be better to leave it and "suck it and see" but i would be monumentally p155ed off after decorating and furninshing the room half of the chimeny decided to fall apart.

I'll go down the rendering route.

i'm a little worried how the render and skim will marry up with the gypsum board and skim, but i suppose thats just a job for my plasterer to worry about. I imagine it will envolve a large amount of scrim!

I have a paddle and i have great experience in mixing plaster etc...

Hopefully my last question but can i use sharp sand for the render? or does it have to be builders sand?

I'll reply with an update once i have done the works and post some pics so you can see what i have done.

 

[Richard C]

Sharp sand is too coarse & more difficult to use; use soft sand for your render.

Please remember in future that multiple posting is not necessary, cause’s confusion & will generally **** off those who have put effort into advising your original thread. Feedback is always appreciated.

 

[guy84]

Noted, thanks again.

 

[guy84]

Richard.

Have finished the room now except carpetting and had the log burner running over the weekend and it was great.

Had the plaster board pulled down and rendered then skimmed with the purimachos heat resistant plaster.

I'll post a couple of phots soon, for a first time fire install and new hearth i'm pretty happy with it.

I have been conducting CO2 and monooxide test and air tightness tests and its all fine.