Pointing Assistance Please

[jrterror]

I have a friend who is considering having their house pointed. It is stone faced at the front, brick at the rear and brick also on the side of the house. Now, they have been there around two years and it appears that they have a lot of damp in the house, and they are wondering if it needs the walls re-pointing. There is a lot of damp behind their washing machine in the kitchen. There are signs that the house has been damp proofed. They said that they had lots of damp in the front bedroom, upon the gable end. Down stairs where my friend’s husband chopped of the plaster in the pantry, he noticed that all the headers were wet. No others just the headers. Again these are on the gable end. I asked if they ever open the windows and they replied “no”. They have actually got a de-humidifier in the house too. So what do you think? Can this amount of damp be caused by poor pointing? You may be thinking, why are you posting this? Firstly, my friend and her fella don’t know anything about building, but know that along time ago I worked with a builder for about a year. Secondly, they are broke and hoped that now I have moved into the area that I maybe able to help out. I have done a little bit of pointing all those years ago, and was fairly neat. But I do realise that there are huge gaps in my knowledge. For instance I remember that it is important to determine what type of mortar was originally used and to re point using a close a match as possible. I think I remember that when pointing stone as opposed to brick that lime should be used to allow flexible joints and allow water to escape. I think cement does do allow this to happen. But I can’t remember what kind of ratios. Do you use cement with lime as well as sand? Or just lime and sand? I really can’t remember these basic things. Do you use lime when pointing brick work?

Sorry, I know that I am asking lots of questions, but I’m trying to help out a friend.
They had some firms price it up but it was over £1500 and they were not even convinced that the 2 out of the 3 contractors knew what they were talking about.

So, I know that I can do the physical work, but just want to learn as much as possible about the technicalities of the work. I know that there is much more to it than meets the eye. Lots of people just come along, chop it out and point it with anything, not worrying about keeping the wall wet, mortar ratios, correct materials for different applications etc. One of the contractors suggested coating the gable end wall with a water seal. But I wondered if this would stop the brick work or mortar from breathing, i.e. lower the mortars permeability.

So any help would be appreciated.

I know that I maybe slightly out of my depth, but I am willing to learn and want to actually, I don’t want to help out if I’m not confident that I can do a good job.

Many Thanks

 

[Nige F]

he noticed that all the headers were wet. No others just the headers. Again these are on the gable end. I asked if they ever open the windows and they replied “no”. They have actually got a de-humidifier in the house too. So what do you think? Can this amount of damp be caused by poor pointing? Many Thanks

Fair Play to you for wanting to help out BUT they have issues with ventilation - or lack of- a dehumidifier is a waste of time . Half of what they are experiencing is the way they are living , all shut up in an old building . Get them to resolve this then see how much damp remains .Meanwhile search the net for historic building conservation

 

[kerek]

Hi i'm pretty new to this website but give a stab at this damp issue.

I think you need to identify whether the damp is rising damp.

Basically old stone and cob buildings generally suffer from rising damp from the ground especially if there is a hill or water course behind them. The rising damp means that water is literally soaked up from the ground like a sponge. Sometimes you can see dark damp patches rising from the ground. It sounds like it is rising damp because the damp patches are on ground level i.e behind washing machine.

To resolve rising damp a plastic sheet (DPM) is cast into a concrete floor. And the walls can be rendered with a layer of tanking slurry which stops water vaporizing into the air.

The pointing issue should defiantly be resolved with lime even if it is brick work. Lime allows breath ability and movement. However, there are many types of lime to use for example lime putty or NHL (natural hydraulic lime). Putty is the text book answer but sometimes NHL is the realistic answer. But cement on stone is a massive no no. In some cases cement can be counter intuitive because frost damage will destroy the stone rather then the self sacrificial mortar. If the pointing is flaking and exposing deep cracks the pointing needs doing for damp and frost reasons.

Overall, its difficult to say with out looking at the job but I think that the damaged pointing will not be the cause of the damp. Unless the walls are really thin and the prevailing wind drives rain into it.

Thanks Sam

 

[jrterror]

Thanks for the reply. So for a mortar mix for a stone wall, what should be the ratio? Is cement used at all?

 

[stuart45]

If the original mortar is lime, use either 2 or 3 sand to 1 NHL 3.5. You could also use lime putty with about 10% brick dust. Make sure you use the right sand with lime. Really exposed work might need NHL 5.0.

 

[noseall]

Hi i'm pretty new to this website.......I think you need to identify whether the damp is rising damp.

Rising damp does not exist.

Read and weep.

 

[noseall]

lime putty with about 10% brick dust.

Can you buy brick dust?

 

[stuart45]

lime putty with about 10% brick dust.

Can you buy brick dust?

You can get it not far from where I live, but there are cheaper places.
http://www.limebase.co.uk/index.php?page=additives

 

[jrterror]

Hi. Thanks for the input. So, is cement not used at all? Also, and sorry for all the questions, what type of aggregate would be best? As formally mentioned it is a stone wall at the front and we are thinking of just pointing this one for the moment. Average size mortar joint.

 

[stuart45]

what type of aggregate would be best? .

A sharp well graded sand.

 

[jrterror]

Hi. Once again many thanks. So, no cement, and a grit sand. Grit sand is the same as sharp sand is it not?

 

[jrterror]

Actually. Anyone who is reading this. the property in question is in Barnsley.
Why do I say this? When using a cement and grey sand mix, the mortar always dries out in an almost bright white colour. Why is this. Is this down to the cement?
Does using lime as a replacement for cement give the dried out mortar a more grey finish? This would be good, cause I hate that really white finish, it looks terrible. We used to add mortar dyes to the mix. But is there a better way of creating a grey finish? A different sand perhaps. If so are there any Sheffield, Barnsley area readers who can suggest where such remedies could be bought?

Thanks again all.