Pointing

[victorianjob]

We are having to re-point the entire house as a lot of the mortar has worn away. I've asked the brickyard to use lime, however I've just found that the mix he has been using is 6:1:1. Sand:lime:cement. I read I'm the Victorian House Haynes manual that a bit of cement can be an acceptable compromise. Does this mix sound alright? There is an awful lot of pointing done, do I continue or ask the brickyard to change his mix?

Btw it's Victorian house constructed from wire-cut red bricks.

Sorry for offloading so many questions!!

 

[Gareth Hughes]

Cement was certainly around in the 19th century, it rather depends what your house is stuck together with (or rather, what the bricks are kept apart with) at present. Bumping this one up for others' comments.

 

[middi]

6: 1 :1 is perfectly acceptable . If the masonary to be repointed is of a very soft nature 7 : 1 : 1 or an 8 : 1 : 1 would be preferable.
The rule of thumb is that the pointing mix must not set harder than the existing masonary and it must be at least as permeable as the masonary.

Middi

 

[MatthewC]

6: 1 :1 is perfectly acceptable . If the masonary to be repointed is of a very soft nature 7 : 1 : 1 or an 8 : 1 : 1 would be preferable.
The rule of thumb is that the pointing mix must not set harder than the existing masonary and it must be at least as permeable as the masonary.

Middi

But how permeable is 6:1:1 really ? And how can you find out (before it's too late) whether it is as permeable as the masonry?

I was once very familiar with a building rendered with this mix, and it seemed that it allowed water through but then retained it!

 

[victorianjob]

Thanks Matthew. My first response was Oh Christ! I have my Dad with me and he was quick to point out that you said 'rendered'. What mortar mix would you say? I've read 9:1:1. Really it's bizarre that the bricky we are using has an excellent reputation and has been laying bricks for the best part of 40 years but seems almost afraid of lime. Could we change half way through? I'll post photos of the brickwork on the other thread.

 

[victorianjob]

Here's a close-up picture of the pointing at possibly the wrong mix Eeeek!

 

[plasticpigeon]

I can't understand peoples fear of lime. I think it is really similar to use to cement especially if NHL is used, except the working time is longer. A few areas of my house (from 1903) which is also built with wirecuts similar to yours was pointed with 1:1:6. The house has suffered movement since and I can confirm that the mortar has cracked without damaging the brickwork so that is a good sign. Having raked some out I still think it is harder than lime though, even NHL 3.5. If your brickie is good and makes a thorough and attractive job, you are onto a winner, as there are many who don't manage that, but you are paying the money so should be able to call the shots. I personally would feel happier if lime was used, but it may be more of an emotional than rational viewpoint!!!!!!!

Intriguing picture, are you happy to put up pictures showing an entire elevation of the property???

 

[Lime]

This sort of thing, mix of cement and lime, was discussed several years ago.
At the time there was evidence that a cement/lime mix is likely to crack after a few years.
I think a trawl through past posts is in order.


Personally I think the so-called lime mortar of 6:1:1 is far too weak for the lime to be of any contributing factor save to act as a plasticizer.
i.e. it isn't lime mortar.
The lime just makes the weak cement mix easier to apply.

 

[stuart45]

General rule of thumb for brickwork repointing is to use a similar mix to the original, but very slightly weaker.
1/1/6 is classed as a cement mortar, being quite a common mix for newbuilds above DPC in the past. Nowadays plaz is normally used instead of lime.
A lot of bricklayers don't like using lime mortar without any cement added because it's unfamiliar to them.
The information from the Smeaton project suggests that a small amount of cement in the mix actually weakens it.

 

[DJH]

Try and save all the raked out mortar, break it down by rubbing it between say two bricks or bits of wood, sieve it, mix in lime and off you go with maybe a bit of fine sand to bulk it if required. If you don't have enough old mortar then rake out the joints a little deeper and fill them with a lime sand mix and then point in with the original mortar mix ........

Doug

 

[middi]

6: 1 :1 is perfectly acceptable . If the masonary to be repointed is of a very soft nature 7 : 1 : 1 or an 8 : 1 : 1 would be preferable.
The rule of thumb is that the pointing mix must not set harder than the existing masonary and it must be at least as permeable as the masonary.

Middi

But how permeable is 6:1:1 really ? And how can you find out (before it's too late) whether it is as permeable as the masonry?

I was once very familiar with a building rendered with this mix, and it seemed that it allowed water through but then retained it!

4 : 1 : 1 progressing to ,say, 9 : 1: 1 ( or 9,2,1--- 2=lime) is starting with the " non porous" to " very porous" . Alternatively one can dispense of the cement altogether and have an extremely porous mix.
The trick is deciding when one should use any of the above mixes relevant to the type of masonary which has to be used
For example , a 4,1,1 mix would be more appropriate for a little or non porous brick progressing to a soft red brick ( or even soft lime stone) where a 9,1,1 mix would be more appropriate ( or in the latter the omission of cement altogether but a lot more lime).
The above is based on 50/50 soft and sharp sand of the desired bulk mix, one part white cement, and one part hydrated lime ( or 2)
A 9,2,1 mix has been used by myself for over 30 years to repoint or lay soft brick exterior walls.
The reason for using cement in the mix was purely for speed of mortar setting and the brilliant way which the mortar joints can be "raked" with soft wire brush a day or so after use in order to obtain a perfect repointing matching existing lime mortar joints. this process can onle be learned with some experience.
Of course one can always use traditional mortar mixes if they have a guilt conscience and a little extra money.

Middi

 

[Lime]

Of course one can always use traditional mortar mixes if they have a guilt conscience and a little extra money.

I don't think it has anything to do with conscience.
It is to do with appearance.
Quite simply, cement pointing after time does not weather like lime mortar and stands out like a sore thumb.
I'm sure I'm not the only one who can spot it a mile off.

 

[Lime]

duplicate.
forum unresponsive.

 

[Lime]

duplicate.
forum unresponsive.

 

[Lime]

duplicate.
forum unresponsive.


................. Even now, several hours later, my post is not shown as last post in the main forum window.

 

[worms]

duplicate.
forum unresponsive.


................. Even now, several hours later, my post is not shown as last post in the main forum window.

Very strange... Just posting to see if it is you or the forum...!

 

[worms]

Even curiouser! I am now shown as last post, but the post itself hasn't appeared! Seems to be only this thread, though!

 

[victorianjob]

Oh heck. Seems we've made a big boo boo with the mortar. Not sure what to do. I have to say, this is really consuming my thoughts. I'm speaking to the bricky on Monday, hopefully will figure out the right thing to do!! I could so with a *scratching head smilie!*

 

[victorianjob]

It seems we've made a big mortar boo boo! Really not sure what to do at this point but I'm speaking to the bricky on Monday and will hopefully figure out what to do!

 

[middi]

I need to clarify my position on the use of cement. Most of the period buildings I have repaired over the years, the majority of the repairs were necessitated because some previous builder ( or other) had indiscriminately used cement when a gap or a hole had appeared in the structure leading to faster decay of the building, therefore I am the last person to advocate the use of cement in these building. The same applies to the indiscriminate use of other modern building materials such as membranes, dpc's, dpm's, paints, pressure treated timbers, modern insulation, nails, screws, etc.. etc,, which would be " alien" and, if indiscriminately used could lead to the deteriment and faster decay of an historic building. Well, I have used all of the above mentioned materials ( including white cement) mostly with the blessing of either a CO or an heritage architect.
Whilst there is no substitute for an exactly like for like repair from an aesthetic point of view ( although patina matching can still be very difficult or at times impossible due to poor availability of period materials) the reality of modern times is that these alternative " modern" construction materials can be used to good effect on these old building , if ONLY one knows HOW, WHERE , WHEN and WHY they maybe a better alternative that could actually prolong the building useful life. Before any of these modern materials ( including limited use of white cement) is used, a proper evaluation of their merits of application in that particular situation should be well understood.

I have noticed on this forum that when the word dpc, dpm, D G, membranes ,cement etc.. is mentioned , the A & E units of the local hospitals tend to get rather busy with people suffering from cardiac arrests. all I can say to those people is " keep reading, learning and keep practicing "

Middi