Is it lime or cement?

[Anonymous]

Hi all,

for one reason and another, most of which I can only guess at, previous owner / occupiers of our house attached fibre boards to some 2 x 2 battoning to our dining room walls.
We're in the process of removing these and I've got the window wall done....

I think there is a lime finishing skim underneath but underneath that Is what looks like sand and cement mortar in some places very yellow and in others quite grey.
I'm not sure if it's actually a lime plaster / mortar / render or actually cement... can anyone take a guess at my bad pictures and give me an idea ?

Also visible from the picture is the oak (?) window lintel which seems to be inside the window frame and not covered by any plaster of any description.... is that normal for an old house ?

Paul.

 

[MatthewC]

Well, Paul, I think it looks like lime mortar but it is hard to say. Have you tried testing a bit with vinegar? If it fizzes, it's lime.

That lintel looks odd - it seems a bit too regular and square so I would have thought it was a more recent replacement, and also it doesn't extend into the wall as much as I would expect. I would think it would be quite OK to leave it unplastered - that would also give an easier job to do than trying to plaster over it and then what do you do at the corner?

 

[Anonymous]

Hi MatthewC,

thanks for the advice... tricky as the only vinegar I have in the house is in a pickled onion jar !!
I tried it on a bit of the white plaster and though it was difficult to see it fizzing I could hear it.

The same can't be said for the mortar... I'm not ruling it out being lime mortar but it is a different colour to the mortar between the bricks and frankly with some of the crimes that have been committed to this house I wouldn't put it past anyone rendering it with cement!

I'll do some more tests before I get all destructive again.

Paul.

 

[Flyfisher]

Try to get some 'Spirit of Salts' from a local hardware store. It's basically Hydrochloric acid and much stronger than vinegar so the 'fizz test' for lime works well. It's also the main constituent of 'brick cleaner' so is a generally useful thing to have around if you're doing any lime mortar repairs and are, like me, a tad messy. Dilute it to around 10-15% and it cleans away any lime splashes and stains very easily prior to washing down with clean water. Take sensible precautions in use.

 

[mrwood]

It looks exactly like my walls unfortunately, which are cement!

Hope it's brittle and ready to ease off

 

[chuckey]

The top picture seems to show little black bits in the mortar. This is wood ash that was used as an accelerator when working with lime mortar and plaster.
Frank

 

[Anonymous]

Ok so I bought some spirit of salts from ye good olde homebase last night.... poured a little into a plastic container and dropped a piece of the yellowy looking stuff into it and I can tell you fizz central !!! So I figure it must be lime mortar which is better news.

So thanks for the tip, problem solved.

Paul.