Boarding and rendering a fireplace.

[paulymarshall]

I have recently rejected some work done at my house by a HETAS engineer. Basically, I bought a house in April that was built in 1965 and am in the process of giving it a bit of an overhaul one room at a time. The one and only job I didn't want to tackle was the installation of a woodburner due to the building regs, and the fact that plastering/rendering is my least favourite thing. Unfortunately for me, the very nice chap who came round to do it obviously shares my feelings on the subject, I have knocked all his plaster and render off, (with very little effort), as he has agreed that it was sub standard. He has agreed to charge me only for thye flue and cowl etc and will be returning to give me the HETAS cert once fireplace has been done. I have now decided that I will tackle the work myself, but need two bits of advice please, firstly, what mix for the render around the burner? I have searched and found many differing opinions. I don't want to use the expensive and probably rubbish ready mixed stuff.

Secondly, I am going to board (then get somebody to skim) the chimney breast, and cannot think how to marry the plasterboard and render where they meet at the opening. I want to put a corner bead in, a normal skim bead will not hold enough of the render, and an external render bead would be too manly for the skim. To all the experts reading this, apologies if there is an obvious fix for this, my brain has given up. Thanks in advance.

 

[Richard C]

Before you go any further read these links;
//www.diynot.com/forums/viewtopic.php?t=211524
//www.diynot.com/forums/viewtopic.php?t=224751
//www.diynot.com/forums/viewtopic.php?t=227100
Some are cross linked but you will get the main points. Basically you cant use Gypsum plaster products within 500mm either side or 800mm above the fire & certainly not in the fire opening if you have a free standing stove. That also includes Fireline or any similar products which are only Gypsum board based & designed for a one off fire exposure, not continual exposure to temperatures above 50 degrees C.

Come back with specific questions if you need to.

 

[paulymarshall]

Hi Richard, I have been reading your posts most of the evening already and as you point out in most of them, Gypsum is a big no no. I contacted the makers last week and had this verified, my so called "pro" had built up my chimney breast with Multi Finish to a depth of 35mm in places. This is one of the main reasons I have rejected his work.

I realize I will have to pay a bit more for the proper heat resistant plaster and boards, what I cant decide on is how to get a good finish on the corners of the fire opening ???

I do wonder how many people have paid my man good money for his multi finish, I had a lovely heated discussion with his wife/business partner today who "assures me without reservation" that her husband has 15 years experience. I did mention he was HETAS didn't I?? Scary.

 

[Richard C]

I realize I will have to pay a bit more for the proper heat resistant plaster and boards, what I cant decide on is how to get a good finish on the corners of the fire opening ???

I assume your having a stove in a recess! There are ways you can do it with boards but, personally, I would opt for sand/cement/lime render base; weather or not you use a heat proof plaster depends on what type of finish you want; render will look rustic (& probably won’t notice on the recess) but a smooth plastered finish is a lot more work. The corners have to be formed in render without beading which is not difficult but more time consuming as it involves battening; you can’t use steel beading because the differential rate of expansion/contraction will cause the render to crack & fail in a very short time. Finish plastering the corners is again done without beading but does require more time & a degree of skill.

I do wonder how many people have paid my man good money for his multi finish, I had a lovely heated discussion with his wife/business partner today who "assures me without reservation" that her husband has 15 years experience. I did mention he was HETAS didn't I?? Scary.

To be fair to your guy; being a HETAS registered installer doesn’t mean he knows anything at all about rendering/plastering & it's not a part of the HETAS registration requirements as far as I know. If he doesn’t know about finishing work, he shouldn’t be doing it but it doesn't mean the installation he's done is not compliant & safe. I’m continually surprised at how often this comes up but I guess it’s a sign of how popular retrofit stoves are becoming & the time of year. Problems arise because many are now trying to marry modern finishing techniques (boards & skimming) with high heat output stove applications & they just don’t go together, especially where a stove recess is concerned or a “modern” no surround look is required.

It’s a common mistake & I only found out the hard way, just a couple of years ago at that; luckily it was my own stove install but it could just as easily been a customers!