Internal brick repointing using lime mortar but which type??

[Dampadoodle]

Hi,

We've converted the loft of our Victorian semi and I've prepared a lovely section of brick work to remain beautifully exposed. This will be about 4 square metres in the far corner of the room. The bricks are tatty and full of character. We're going to stick a renovated old Victorian radiator in front of it. Ideal Classic I believe. Very exciting. Anyway, I digress.

I'm now ready to do the repointing and I obviously want to use some sort of lime, not any of that (get ready to hisssss) cement based mortar...booooooo to that!

So now I need to decide exactly what type of lime mortar to use. The variables are:

- Colour
- Coarseness of aggregate
- Use of a Natural* Hydraulic Lime (e.g. NHL 2 or NHL 3.5 or NHL 5) or use a lime putty based mortar (e.g. Coarse Stuff) (*Edited - previously wrongly read "Non-Hydraulic Lime" - thanks for the advice, Roger! - see post below)
- How to finish off the mortar (flush, non-flush etc)

The bricks are a heady mix of red and yellows and many between the two - so chalk white may be too strong in terms of colour contrast. I think I'll go oatmeal.

As for the type of mortar I've called lots of suppliers and they all differ in their advice. Some say putty (although this takes a long time to go hard) and others state categorically that it should be NHL 2 and nothing else. Apparently it all looks the same when dry. I'm looking for something premixed and dead easy to use.

I'm a novice with a pointing trowel if that helps you to help me.

I'd love to hear your thoughts regarding all the above. And, no, I will not "get someone in to do it" a) because I want the pleasure b) because most contractors just want to shove in cement c) because I like a challenge d) because its cheaper!

Over to you & thanks in advance,

Dampadoodle.

 

[Andrew Bodenham]

Dampadoodle,

I'd use a mortar made with lime putty as this is nice and fat to work with and gives lots of time for you to fiddle around without worrying about it setting. And if it all goes wrong you can take it out the next day and try again.

Buy in ready-made putty and add about 2.5 times the volume of coarse sharp sand - this is where you'll have to experiment with test areas and different mixes to get a colour result you're happy with. I'd make the mix very dry - probably no added water - so that it is just cohesive, a bit like pastry after you've rubbed in the butter and have added about half the water. This will help to avoid staining on the face of your bricks. (Exposed internal brickwork is a whole other can of philosophical worms, of course.....)

Damp the wall before starting with a hand sprayer or garden presssue sprayer. You've previously raked out the old pointing if defective, and hoovered the wall to remove dust and debris.

Apply the mortar with a skinny finger trowel, filling the joint firmly. Don't overwork it. Horizontal courses first, then perpendiculars. Cover the session's work with damp hessian and leave for a day or two to firm up. Once just hard you can whack it with a stiff brush (churn brush) to compact the mortar, close up any cracks and reveal some aggregate. This process will aslo knock off any excess which has spread onto the brick faces. You can always clean up any smears with a stiff brush, sponge or cloth at this stage. Keep the setting mortar damp for a few days by spraying / covering to prevent cracking.

Pointing is a skill best learned by watching somebody who can do it, e.g. on a lime course. But many people make a good job by reading up, experimenting and just having a go. There are some interesting lime pointing vids on youtube - not all follow textbook procedures.

The great thing about puttty mortar is that you can make up a big batch of your developed recipe and keep it in an airtight container for months - allowing you to do a bit of pointing whenever you have some time whilst not having to mixup a fresh batch of mortar each time.

 

[plasticpigeon]

I don't think it really matters inside. If you want easy, how about using 1 part NHL2 lime powder to 3 parts sand and add water to make a stiff dough like mix. I like using plastering sand but the mix will be a pale buff colour. To get a stronger colour you can experiment by substituting some of the plastering sand with red or yellow building sand, or even easier, add some cement dye. The dye is in the form of a fine powder which disperses in the mortar to give colour, and I believe is usually iron oxide or earth based colour so no probs using it with lime.

My opinion is that pointing looks best when the brick edges or arris are just visible, and I like flush pointing where the pointing mortar is pretty much flush with the brick face or a mm or 2 recessed. This can be done by filling the joint, letting it go off a bit, and then rubbing with the end grain of a piece of wood to flatten it out. finish by brushing lightly with a soft brush such as a brush from a dustpan and brush to remove any feathery bits and make the surface a bit more even. For more impact you could do a ruled joint where lines are ruled into the mortar adjacent to the brick edges.

 

[Keithj]

Having done a fair amount round the house with plain lime putty, and a bit with NHL, I would say "avoid NHL if you don't have to use it".

That's purely because plain lime can be kept indefinitely (in an airtight pot, and with a thin layer of water on top), whereas NHL will "go off" once you've mixed it, so you waste more. As far as I can tell, there's little difference once they've set. I also like the "premix" approach with the ordinary stuff.

 

[Roger H]

Hi Dampadoodle.

If it is internal and you want to keep costs down, and also reduce any wastage, I'd be inclined to use hydrated lime. Keeps indefinitely once batched up if air is excluded from the tub, and if you mix up the dry lime with water first, to form a putty, once integrated with the sand it will leave you with little flecks of white - more attractive than the consistency of hydraulic lime mixed dry with sand and wetted.

Roger

p.s. in your orginal post when you say '- Use of a Non-Hydraulic Lime (e.g. NHL 2 or NHL 3.5 or NHL 5)' what you mean is '- Use of a Naturally-Hydraulic Lime (e.g. NHL 2 or NHL 3.5 or NHL 5)'.

'Non hydraulic lime' would either be hydrated lime or slaked lime.

 

[Dampadoodle]

Hi Andrew, Plastic, Keith and Roger,

Thanks so much for your responses. As expected there doesn't seem to be one 'best' solution.

The area of exposed brick is only small so I don't expect to have any need for the materials once the job is complete. So this minimises the benefits of the putty approach in my view. Having said that, the continued "workability" of the putty is a real benefit in my mind.

Its very interesting that there is not much difference in appearance once hard.

Do any of you have photos that you could share to show the internal pointing and the colour produced using your different methods?

Also, where should I get this stuff? I have found Conserv (lime-mortars.co.uk), lime-stuff and old house store.

Any others?

Cheers,
Pete

 

[steveb]

not sure if this link will work - shout if not.

https://plus.google.com/photos/1142...5860138294300111330&oid=114266060510111771379

pointed with about a 3:1 mix of plastering sand and singleton birch NHL 3.5.

NHL 3.5 was chosen because it was all the local builders merchant stocked, and they said it would be suitable. Nothing more scientific.. We did a test area first and like the effect, the joints were rubbed over with a piece of 25mm polypipe to indent the pointing a bit (I'm sure there is a technical term for this)

-Steve

 

[Dampadoodle]

Hi Steve,

Thanks for sharing - I like the photo!

The pointing looks great. As our bricks are a different texture and colour I think that we may well go for a coarser mix with larger pieces of aggregate, either a "medium" or a "coarse" and then, just as its getting a little hard, hit it with a brush to reveal the aggregate. At least, that's the theory!

Thanks again for posting that photo. Much appreciated.

D

PS - isn't it funny how, when you're planning pointing, you notice it EVERYWHERE you go!

 

[steveb]

here's what it looked like "when wet"

https://picasaweb.google.com/lh/photo/xMV2ujwqx_8ta1Chr9V7tMH2yI2RE1oxoVLSxazqoUM?feat=directlink

you can see it dried from quite a dark yellow colour into something nearer off-white

-edit-
For reference, this is a "before" picture of the same fireplace...

https://picasaweb.google.com/lh/photo/VckLt0hAY3fi873tZJMAXnufpLwTpkooASG7U0yotfY?feat=directlink

 

[Dampadoodle]

Woooooah! Steve what a transformation!

I have a question for you - is that lime plaster on the walls?

Pete

 

[steveb]

in the before picture, no. (nor was the wood "structural", the place was decorated in the "style" of "ye olde country pub" when we got it.) And the step in the floor, it transpired was a second floor, installed over the first one where the first one had almost entirely rotted away due to being in direct contact with the earth underneath.

in the after picture, only the pointing and the fire back was in lime, the walls as you may be able to see in the during one were plasterboard and skimmed , then painted with Earthbourn clay paint which has a rough Matt finish which really suits.

Collecting links in one place:

Before : https://picasaweb.google.com/lh/photo/VckLt0hAY3fi873tZJMAXnufpLwTpkooASG7U0yotfY?feat=directlink

During: https://picasaweb.google.com/lh/photo/xMV2ujwqx_8ta1Chr9V7tMH2yI2RE1oxoVLSxazqoUM?feat=directlink

After: https://plus.google.com/photos/1142...5860138294300111330&oid=114266060510111771379

The observant may notice that we re-instated the load-bearing wall where the step in the floor was. It came in handy, holding the house up. How it didn't fall down is still a mystery - the upstairs floor was like a giant trampoline, you could see the entire ceiling bounce as people wandered about in the bedroom...

Here's a view from a similar angle to the "before" picture. The windows and flooring make a hell of a difference too

https://plus.google.com/photos/1142...5860138179827167378&oid=114266060510111771379

-Steve

 

[plasticpigeon]

Hello Dampadoodle,

Please excuse the dirty brickwork, I am in the process of repairing and painting the bay window, but this illustrates the style of flush or slightly recessed pointing that I like. I attempted to match the colour on the rest of the house by using a mixture of mainly plastering sand with added red and yellow building sand to make the pale orangy brown mortar colour. The wide joint in the middle is for the slate damp proof course.

 

[Dampadoodle]

Hi plastic.

Thanks very much for posting that photo. I see what you mean about the recessed look- it works very well. I am planning on doing something similar. My folks used to have some exposed brick on their lounge that I loved and the pointing was recessed a large amount....I loved it. Then they went and plastered over it.

I now need to find a load of different options to order and have a play about.

Dampy

 

[Zebra]

Whereabouts in the country are you Dampy? There may be other suppliers near you. There's Mike Wye, Ty Mawr, and others. I get NHL from a local conservation building company who will sell people materials from their depot. I get hydrate from a normal builders merchants.

 

[Zebra]

This is internal. The whiter mortar is original. The yellower stuff is replacement, it's Old House Store's coarse stuff but you could make similar from soft sand, sharp sand and putty.

 

[Dampadoodle]

Hi Zebra,

Thanks for the response and the photo. These are really useful as I was considering Coarse Stuff from Old House Store. I have a mix of yellows and reds and I now think that actually I need something a little paler.

I'm in Sevenoaks area if that helps.

I'm tempted to get the "biscuit" samples from Mike Wye http://www.mikewye.co.uk/Lime Mortar sample biscuits.htm but they are a little pricey....anyone have a set they want to offload at all?

At some point I will upload a photo of the project.

Cheers,
Dampy

 

[Dampadoodle]

This is an example of the untouched bricks in the loft. They were obviously the rough ones that the brickies decided could be used up in the loft where they wouldn't be seen (back in 1875).



This is a picture of the bricks after I raked out most of the original mortar. I love their character, chips, cracks, damage and all!



This is what they look like now, following cleaning. Almost ready for repointing.

 

[Dampadoodle]

So, considering the above...what colour would YOU choose?!

 

[Dampadoodle]

I think I'll go nice and white. Similar to third from the left, top row.

 

[Zebra]

I'd have to agree with your colour choice. Any of the first three. They're all very nice. You can tell straight away it's lime not cement, with bits of black in and a nice texture.