Pointing a Brickwork Chimney (Not Boaty!)

savageseadog

savageseadog

Well-Known Member
Joined
19 Jun 2005
Messages
23,291
Visit site
Had a good Google around but nothing obvious. What's the answers to the following please:

1) Depth to rake out/grind out?

2) Morter mix or use something else?

3) Is it a good idea to use a bonder like PVA?

4) Same morter or whatever for round the chimney pot (is that the crown?)
 
Ready supply of mortar-like substance.

storks-on-chimmney.jpg
 
This is supposed to be a 'Reader to Reader' section, not Reader to Render'.....

/forums/images/graemlins/laugh.gif
 
Rakeout for aprox 3/4" deep.
Use 3 sand to 1 cement no lime.
Dont use PVA, its not water proof.
Do use a very small drop ( couple tea spoons to 4 ltr water) of washging up liquid which will make the mix very supple and easy to work with.
You can use the same mix for around the pots, or coping, but if a wider area is to be filled, add some crushed granit to it which will make it very strong, (Not for the pointing though)
I mixed my first 10 barrow batch of concrete by hand when I was 9yrs old had it ready for dad comming home from work to lay it. Its still there.
 
Don't use washing up liquid.
It will make the mortar fail within a few years.
Use a proper mortar plasticiser. You can get this from any builders merchant.
Follow the instructions carefully.
Over use of this will also weaken the mortar over time.

The strength of the mix depends on the softness of the bricks in the chimney.
If the bricks are an engineering type (Very hard) a 1:3 mix is fine.
The mortar should always be weaker than the brick.
If the bricks are a soft red a 1:3 mix will cause the bricks to be weathered away rather that the mortar. for these you should use a 1:6 mix or weaker.

Re-pointing every so often is a lot less expensive than rebuilding the chimney.
 
To secure a chimney pot in place the stuff you need is called "compo"; [I think as someone earlier has said it has perhaps granite chips in it, but whatever, it is VERY hard when you come to break it up!] to use with cement to make your mortar.
 
They're a lot bigger when you get up to them than they look from the ground. I did ours last year - thought I'd have it done in an afternoon. Three days it took /forums/images/graemlins/frown.gif. I'll pay someone to do it when it needs doing again.

4" grinder with diamond wheel is best for raking out (<£10 from Makro), but be carefull not to catch the bricks. I used 6:1:1 (concreting sand:cement:lime) as the bricks are laid with lime mortar - Take heed of the advice above: the pointing needs to be softer than the bricks. I also used PVA (for no real reason, other than a roofer I know said to). Moot point as to whether pointing needs to be waterproof.

I think the stuff on top (benching?) needs to be a bit stronger, and waterproof - I'd probably use 3:1 with a waterproofer, unless I could find some advice not to. I didn't touch the benching last time, but I need to do it now. GRRRR /forums/images/graemlins/mad.gif

[edit]: I would probably mix 'grano' concrete for the benching; i.e. granite chippings, as suggested by others - round here, 'compo' = 'muck' = '[--word removed--]' = generic term for mixed mortar or render.

Andy
 
The easiest way to rake out is to use an angle grinder, But be sure to shut all your windows and doors first, and don't forget to warn the nieghbour as well. Also if the chimney is in poor condition, grind out to a depth of 1 inch,start at the bottom and work up. point up the bottom first. The weight of the bricks above will hold everything in place. If you start at the top every brick you touch can be disturbed and you could finish up dismantling the whole chimney
 
You must log in or register to reply here.

Share this page

Top