Parge behind my fireplace

[AliG]

I am almost done with filling in all the gaps the builders left before I get my second airtightness test.

 

One job I have been putting off doing, but want to do is the inside of the chimney breast.

 

The idiots put the large coat on the outside of the chimney breast, and did not parge inside it before putting the fire in, despite being asked to a couple of times.

 

It is obviously draughty in there. I cannot figure out exactly where the draught comes from, it might be a number of places. Inspecting it, there is around a 10mm gap at the top under the slab, so that may be allowing air in from the cavity.

 

There are also vertical gaps between the blocks as Porotherm does not have mortar in the vertical joints and various gaps in the corners where it meets the outside wall. There are door frames behind these gaps so they may also be a source of air leakage.

 

I have tried foaming up the largest holes, but having looked at it I cannot foam up all the vertical joints. It is also difficult and messy as I am working through a roughly 400x600 hole at the side and some areas are around 2m away from where I have to work.

 

So I was thinking  of using a long brush to try and parge the walls.

 

The area is only around 4-5 square metres so I don't mind about the cost/m of what I use. Just something easy to mix up and that won't drip and run al over the place. It also needs to be able to fill in gaps around 10mm wide.

 

I was thinking of buying this.

 

https://www.amazon.co.uk/Bostik-30812571-Cementone-Render-Repair/dp/B01D8FRGMI/ref=sr_1_1_sspa?keywords=plaster+render&qid=1636887565&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyQko4Q1hRWlU1NFBHJmVuY3J5cHRlZElkPUEwOTQxOTU0WkFYUVJaWFMyUE9IJmVuY3J5cHRlZEFkSWQ9QTA4ODEyNDgzMjFWNEw1U0ZDT1lUJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

Any thoughts?

[dpmiller]

spray with an extension nozzle? Bit like a schutz gun for rustproofing

[JohnMo]

Big gaps, sand cement.

 

I did a parge with a thin cement mix, for this I used 3 sand (not sharp sand as it's too gritty), 1 cement, and about 1/5 lime.   Applied with a broom.

[AliG]

Thanks @JohnMo

 

What’s the water ratio I would use in that mix?

[JohnMo]

I added until I had a double cream thickness

[AliG]

Off to B&Q later.

 

Absurdly it looks like I have to buy 25kg of lime.

 

I'll post the results when I am done.

[TonyT]

Should you have pipework and cables in a chimney?

 

[AliG]

It's a fake chimney. There is a twin wall flue that goes out through the wall. That's the top of it in the bottom picture.

[AliG]

OK, a very messy morning -

 

I made up the mix and was really struggling to get it into the holes.

 

The problem is that I am working through a small opening and cannot get the right angle on the brush. I was using a small broom and at full stretch between the head and the mix on it, it was very difficult to control.

 

So I tried a small roller and a small brush taped to the end of a pole. These worked much better and I could work the mix into the vertical joints.

 

But I suspected that the main issue was the space between the first floor slab and the outside wall.

 

In the end the only way to fill this was foam. I attached an 8mm pipe to the can and attached the pipe to a brush handle.

 

I had tried this before but was running into problems at maximum reach. I ran out of hands to both keep myself steady and squeeze the trigger. Plus due to leaning from a set of steps at a steep angle the step would start to slide out from under me.

 

This time I enlisted my wife. She held the can and squeezed the trigger as well as standing against the steps so they did not move. This worked much better allowing me two hands to direct the foam and hold myself steady.

 

It feels a lot less breezy  in there now.

 

I am also taking this opportunity to put a wifi extender in there to get a better signal out on the terrace. When you close triple glazed doors that pretty much kills the signal and sometimes I want to sit outside and stream stuff.

 

Just waiting for the foam to dry to scrape some of the droppings off and tidy up.