Replacing grout/mortar between hearth stones under hearth

simonsmithsays

Afternoon folks

Moved into a house with a few issues.

We have this log burner which sits on two hearth stones.

The mortar between the stones has turned to a sand like consistency in places.

Can anyone give any advice as to what product (and tips) to use to replace this after I've raked the loose stuff out.

The gap is around 20mm and the stones around 60mm deep but I don't know how deep the loose stuff goes yet.

The working space is tight and will obviously get hot.

Thanks in advance folks

grumbler

I'd use grey grout.

https://www.screwfix.com/c/sealants-adhesives/grout/cat850090?brand=no_nonsense

simonsmithsays

grumbler said:

I'd use grey grout.

Appreciate the reply @grumbler

Do you think this grout would be ok for an area which gets so hot? 

stuart45

The joint.looks like sand/cement mortar, which tends to break down quicker than lime mortar in hot areas. A rule of thumb for pointing is to rake out a depth of double the joint width. So 40mm here. 
There are special heat resistant grouts, but they aren't cheap.
I'd use a lime/sand mix. The mortar needs a bit of body for a bigger joint like this, so a coarse, sharp sand would be better.
Rake out all the way along to get an even colour.

FreeBear

stuart45 said: I'd use a lime/sand mix. The mortar needs a bit of body for a bigger joint like this, so a coarse, sharp sand would be better.

And if you want any colour other than an off white, mix some pigments in with the lime. I've used artists acrylic paints before now to add a bit of colour to lime.