The Right Mixture – or Pointing In The Right Direction
Hi Folks! I’m doing a quick upgrade to this page today (21st July 2016) as it receives a lot of visits. As you will be aware, I am not a builder, so the story below is my own experience and anything I write is only OPINION. To save you having to read it all, there are some firms who do the right materials (as I understand it) and I’m giving you links to those as well.
Some rules I have found:
Mastic Pointing: Use ONLY Double-Boiled Linseed Oil. NOT Linseed oil. NOT Boiled Linseed Oil.
Rake Out loose material and get the dust out too. Paint the areas to be pointed with Double-Boiled Linseed Oil before pointing. Mix mastic first and let to stand a little then mix again.
Pointing. Do the pointing when you have three or four fine days temperatures of 15 degrees or more without rain. It takes that long to go off and it needs that temperature.
Only use BURNT SAND. You also might have to improvise tools for fancy work. You can go proud of the brick if you like or go smooth and flat (not tucked in) to the face of the brick.
You can paint the brick with the DOUBLE-BOILED Linseed Oil but Watch Out! 1) don’t do this while the pointing is still soft. You will pull it out and smear the sand on the bricks. 2) the rain always gets behind it always and it will go grey. After it has dried out again, it will cease being grey. Beware: You cannot paint over burnt sand mastic with paint.
Warning: As far as I know, Mastic Pointing has NO structural properties. It is NOT a substitute for mortar, sand and cement etc.
I have no connections with any of these suppliers.
(Yorkshire) WOMERSLEY’S http://www.womersleys.co.uk/shop/stone_repair_and_mastic# (I have used this supplier and they were very helpful)
Ravensthorpe Indust Est, Low Mill Lane
Ravensthorpe, West Yorkshire
Tel: 01924 400651
MULTICRETE Products Ltd 01706 212135
http://www.multicreteproducts.co.uk/double-boiled-linseed-oil-1l-25l-or-5l-270-p.asp (I have used this supplier and they were very helpful)
Multicrete Products Ltd
Unit 1 Commerce Street
Carrs Industrial Estate
And there are other suppliers too if you have a look on the web. You can also buy trowel mastic ready mixed with added dyes. Or you can add dye to it. The usual colours are a dull red or a gold sand colour, or white. Sand colour affects the colour of the finished product too.
http://lincolnshirelime.co.uk/traditional-sand-mastic–oil-10kg-tub-2272-p.asp (I have not used this supplier but found them easily on the web)
(Edinburgh)http://www.masonsmortar.co.uk/knowledge/page/burnt-sand-mastic (I have not used this supplier but there is a lot of information here)
Have fun! Remember, I am not a builder. Anything I have said here is my personal opinion.
Here is my Story…
About three years ago, an old builder sorted out our brickwork – by sharing knowledge.
Having knowledge is good and it usually benefits one person. Using knowledge is laudable and it usually benefits some people. Sharing knowledge is magic and it benefits many. Usually those who are really secure in their skills will share knowledge. Unwillingness to share knowledge is not a good sign.
House Falling Down
The problem was our brickwork. The building was constructed using lime mortar. The house is in a very exposed area. The pointing was decaying rapidly. It was raining in. When it was re-pointed using cement (four to one sand and Portland cement mix), the wind dried it to such an extent that within ten months, it had blown and fallen out.
Getting It Wrong
Chatting to an older builder working on our neighbour’s house, he came to see what I had done wrong. “And you used four to one?” “Yes” “And you raked it out properly and sprayed water before you pointed?” “Yes”. “Well, there must be something wrong what you did. The only other thing I think you could do” (and here, he laughed a bit, inwardly) “is to use mastic“.
“Is that what they would have used at one time to fix window frames?” and suddenly, I remembered that I learned something when I was a boy.
What Is Mastic?
“It’s not that stuff you get out of a tube”, he said. “Not what you put round your bath. It’s what the old builders used and it lasts for years. It’s nice to work with too. You have to buy Double-boiled Linseed Oil and Burnt Sand. Then you mix it up and use it just like mortar for pointing. Remember, this is what you use for pointing over lime mortar. Double-boiled-linseed-oil and burnt sand. Mix it up and use it”.
So then we had to source it. Not easy. And what is “Burnt Sand?” – I wasn’t aware that sand would burn! In the end, we think that it means “kiln dried sand” or sand where all the moisture has been driven off. Certainly, ordinary building sand will not work. It has far too high a moisture content.
The internet was very useful. We found the stuff; drove sixty miles, came home and looked at what we had bought. It did not look correct.
There are some times in your life, when somebody has shared knowledge with you and you think “They must have been pulling my leg”. This was one of those times.
I decided to mix some up. But how much? And to what consistency? Also, each section of joints that was to be pointed had to be painted with the “Double-Boiled-Linseed-Oil” first, to make a key. This meant that the oil had to last for painting the raked-out mortar and also for mixing.
I need not have worried. I measured out one tablespoon of double-boiled-linseed-oil into a small plastic container. Next, I added one teaspoon of burnt-sand. That was not enough. I added more, little by little, until it had a consistency that could be pressed into the joints by a knife.
Instructions – A Bit At A Time
I went out to the front of the house. I chose an area about one square foot to work in. I raked out the broken cement. I got in the joint to the original lime mortar. I brushed out the old powdered mortar. I painted double-boiled-linseed-oil into the joint. I let it stand a little. I took some of the mixture on to the knife. I pushed it into the joint. It fell out. I tried to pick it up. It felt like butter. I left it on the pavement.
I started again.
Work Slowly – It’s A Slow Job
I added a little more sand to make the mixture a bit drier. I took a blob about a quarter inch square. I pushed it into the corner. It stuck. Then I took another bit and stuck it to the bit that had stuck. Now it did not fall out. By adding tiny amounts and making sure that they were stuck to the bits that were already stuck, the job got done.
The smell of the double-boiled-linseed-oil took me right back to my grandfather’s home where he was having his sash window re-fixed fifty years ago. “What are you using?” I asked the man working; “What’s that smell?” “It’s mastic” he told me. “So remember, you need that round your windows”.
Slow To Set Hard
The square foot was completed. It looked good. However, it was a soft as butter. I went back to it just as dark was falling. It was still soft. I told myself this was a failure.
Next day, we went out and looked again. Neither of us could believe that it had set. It was hard as rock. To be very truthful, it did not look too good either; the joints were not neat. But now that I knew it was set, I thought that I would try some more and make it neater. That I did and now I have bought more and intend to finish the whole building with it.
The blob that fell on the pavement is still there. It is immoveable – as hard as iron!
Remember To Buy Double Boiied Linseed Oil
You can buy ready made mastic. It’s called “Trowel Mastic” or “Builders Mastic” and it comes in tubs. You have to mix it again when you use it. Otherwise, the ingredients are as follows:
Double Boiled Linseed Oil
Mix carefully and use.
Remember too that this job has to be done in warm dry weather, days over 15 degrees centigrade are best.
It is disappointing to see that people don’t know about this stuff for old buildings. Even when I was in Freiburg Cathedral and when I visited Bolsover Castle, it was evident that the restoration was using the wrong stuff (cement) in the joints. Surely, the original builders would have used mastic. It goes way back in time.
Originally, the driers added to the oil were powdered lead and chalk. I would not mind betting that material like this goes way back to Roman times.
Remember though, Double Boiled Linseed Oil is for mastic.
(Raw Linseed oil is for Cricket Bats and Boiled Linseed oil is for applying to wooden interiors).
Fine Pointing For Accrington Brick Too
Mastic pointing can be used very finely too for pointing very hard bricks, like Accrington Brick. If you look carefully at older houses in the North of England, you can see this pointing and it was often dyed a red colour or sometimes a sand colour or even white. Sometimes, it even looks like lead, if used inside a building!
On older houses, it was used with common brick to point. When it was done, the pointing was more often than not, flat with the brick, or proud but not “tucked” in.
Using It To Help Keep Bricks Dry
Finally when the job was completed, the bricks were painted with the Double-Boiled-Linseed-Oil and that makes a waterproof coating that lasts a couple of years before needing re-done. Beware that it can go grey in the rain but it does mature well. I will add the photographs later in the year.
Have a try.
Thank you Neil for sharing.
Please read the disclaimer below:
Please note: No guarantees or warranties are made or suggested or implied by any claims made in this blog. This information is being shared here by an unqualified amateur. Any use or employment or experimentation of any kind with materials mentioned here is carried out at your own risk; observe all safety warnings if working with hazardous materials; always clean up; always work safely using goggles gloves hard-hat and appropriate footwear and wash hands after use.