Repairing old brickwork and having extensions

[spot]

Hi All,

House was built in 1894. Because of it's age will there be anything odd about the mortar/cement (eg: lime?) that I need to know about and how can I tell?

Some of the brickwork is a bit frost damaged and i'd like to get it replaced. If there is anything odd about the mortar do we have to try and use the same old stuff or can my builder get away with using modern cement? Are there any issues?

We're looking to extend. Does the builder need to take anything into consideration when mating modern new bricks to 117 year old bricks?

I'm asking as I seem to remember reading something about damp issues if you're not careful mixing up old and new builds due to the fact lime mortar 'breathes' and allows trapped water to evaporate and modern stuff doesn't?

Finally, I was recently up in the loft and noticed some of the mortar at the very top of the house is a bit powdery and just running my fingers along the mortar was causing it to fall away from the bricks like sand! What the hell is going on here? :shock: Should I be concerned?

Cheers!

 

[AMc]

Some of the brickwork is a bit frost damaged and i'd like to get it replaced. If there is anything odd about the mortar do we have to try and use the same old stuff or can my builder get away with using modern cement? Are there any issues?

Frost damaged bricks may well mean that the house has been repointed with a cement based mortar over the top of the original lime which has damaged the surfaces (caused them to "blow") or it may mean they're old powdery bricks.
Lime mortar will have been used on the house originally and it is compatible with soft old brick as it is porous and allows moisture to move.
Cement mortar is much less porous than soft brick. If you use cement based mortar on soft brick the brick is more porous than the cement mortar so the brick becomes saturated and if you get a hard frost the water freezes and damages the brick. There are some garden walls near me that show a lattice of cement mortar in front of bricks that look like they've done the rounds in a drum mixer (I posted photos a while back).

The old house should be done with a lime mortar - the new extension may not need to be. If your builder doesn't understand the difference then you will need to research and educate him/her or perhaps go for someone with more experience in traditional methods. Unfortunately a lot of respectable and very experienced builders have been working in cement their whole careers and don't appreciate how damaging the wrong materials can be on an older house. Expect comments like "cement lasts longer", "cement is stronger" and have the responses ready.

 

[spot]

I've been in the place since 1996 and the blown bricks weren't repointed while i've been there (and have just blown in the last 2 winters).
You have got me thinking now though... We had some insurance work done following a mild earthquake a few years back which resulted in some bricks being removed and metal strengthening put in and then all bricked up again. I bet the fekkers would've just used modern mortar. I'm hoping as this was just restricted to a few key areas of the house it won't be an issue. Certainly i'll keep an eye on those areas from now on.

 

[spot]

Can anyone else provide any further details on what special steps a builder must take when adding an extension using modern materials to an old house that used lime mortar?
I've never had an extension done before so i'm just trying to get as many "facts" together about the correct procedure of melding old and new building work together as the builders could feed me any old line of bull***t and I would be none the wiser.

Even better, can anyone recommend any builders in the West Midlands (Solihull) area who are sympathetic to working with old buildings?

 

[skier-hughes]

try
http://www.croftbc.com/
http://www.midlandsrestoration.co.uk/

No direct experience of either, but they are local.

 

[tobydog]

Spot - my sister has a Victorian detached house of a similar age to yours. She also has exactly the same issue in her loft. The lime mortar runs through your fingers like sand from an egg timer. You can't even touch it. Up in the loft you can see the brickwork which is very poor and the walls very thin. Unfortunately the outside was completely covered in black bitumen which would have blocked the normal breathability. I'm guessing but maybe excessive condensation in the loft couldn't get out and caused the subsequent mortar decay. Is your outside wall covered with anything?

Unfortunately my sister added to the bitumen (to make it look better!!) with one of this sealed for life type coatings. You could have run a car on the fumes. Awful stuff. If I knew then what I know now.................!!!

 

[spot]

Spot - my sister has a Victorian detached house of a similar age to yours. She also has exactly the same issue in her loft. The lime mortar runs through your fingers like sand from an egg timer. You can't even touch it. Up in the loft you can see the brickwork which is very poor and the walls very thin. Unfortunately the outside was completely covered in black bitumen which would have blocked the normal breathability. I'm guessing but maybe excessive condensation in the loft couldn't get out and caused the subsequent mortar decay. Is your outside wall covered with anything?

Unfortunately my sister added to the bitumen (to make it look better!!) with one of this sealed for life type coatings. You could have run a car on the fumes. Awful stuff. If I knew then what I know now.................!!!

Interesting!
Until about a year ago the loft was pretty inaccessible so I seldom went up there.
Now we have a bigger hatch, ladder, decent lighting and flooring so i've been able to get up and have a good poke around which is how i've discovered this dodgy mortar. I have no idea if we've suffered from excessive condensation in the past but i've seen no evidence in the last 12 months since the loft was done but i'll keep an eye out for it. Nothing has been applied externally that could trap moisture that i'm aware of.

 

[stuart45]

Can anyone else provide any further details on what special steps a builder must take when adding an extension using modern materials to an old house that used lime mortar?
I've never had an extension done before so i'm just trying to get as many "facts" together about the correct procedure of melding old and new building work together as the builders could feed me any old line of bull***t and I would be none the wiser.

It's normally a simple job, although you would usually step the facework of the new work back from the existing. This looks better as the new metric bricks will be a different size from the Imperial ones.
The new work will normally be tied to the existing with wall starter kits.

 

[Feltwell]

This looks better as the new metric bricks will be a different size from the Imperial ones.

I think it looks better even with imperial sized bricks as there is always some visual difference between old & new, which a change of line - even if only a few inches - helps break up. But why not get yourself imperial sized bricks? They will look much better.

There are plenty of salvage yards in the West Midlands that deal solely at the "grittier" end of salvage, i.e. bricks and other building materials. Some of the posh salvage yards around are not far off being antique shops, complete with showrooms with displays of soft furnishings and Farrow & Ball paints. They sell bricks as well but oh boy do they charge for them.

Coventry Salvage are good, Cawarden are horrifically expensive and best avoided, Gardiners in Stoke I highly recommend - all my garage bricks came from him, nice guy, a very good selection and he did me a great deal after a prolonged period of bartering! But there are plenty of small yards around the West Midlands, it's just pot luck if they've got what you want. Bear in mind to check carefully what you're buying as the quality of how bricks are handled & cleaned up varies considerably, and expect at least 10-15% reject rate. If you've the time to drive around them - preferably taking a few of the bricks you're trying to match to with you, but if not they'll give you samples (just make sure you label them!) - you could save yourself a lot. Cash is still king in the small yards.

You should be able to get a good match to Late Victorian bricks, they are generally quite plentiful around the area. If you're struggling it can be worth looking further afield - part of my house has a certain facing brick from Ruabon in Wales that proved very hard to get, I found that an Accrington brickyard and a Stoke brickyard made very similar bricks even though their clay was from a different source.

Or - Furness brick make new bricks to imperial sizes, they supplied for all the new "Victorian" buildings that went up recently in the Canal Street project at the Blist's Hill open air museum in Ironbridge. Lovely product but not cheap though.

http://www.furnessbrick.co.uk/

Roofing materials - there is a great litle yard in Small Heath, very grotty like all the best yards! Good selection - I managed to get a load of tile-and-a-halves from him, which are generally like the proverbial rocking horse droppings to find. He wasn't expensive either.

 

[Feltwell]

Finally, I was recently up in the loft and noticed some of the mortar at the very top of the house is a bit powdery and just running my fingers along the mortar was causing it to fall away from the bricks like sand! What the hell is going on here? :shock: Should I be concerned?

Cheers!

I'd say No. My present and past houses have all been like that, in fact the worst was a 1930's house where you had to be very careful when drilling into any walls to avoid dislodging bricks.

I tend to take the view that your house has been there for over 100 years and that if it was a problem you'd know about it by now! It's not going to have been a sudden change.

 

[Zebra]

Can anyone else provide any further details on what special steps a builder must take when adding an extension using modern materials to an old house that used lime mortar?

I don't think there's one single answer to that. I don't think the fact that the old bit's got lime mortar will affect decisions regarding the new bit. The new bit will comply with all new Building Regs concerning foundations, insulation etc, and as for how it ties in to the old part, I don't know, I'm no expert, but where I'm having a new extension on an old house, my builder says there will be a movement joint between the two because the old house has no foundations and the new bit will have. I'm not sure exactly how this will work. But in other circumstances other ways of joining the two might be appropriate. I don't think the fact that the old house has lime will affect how it's done.
However, the new part may have different ways of dealing with damp from the old part. If the old part has no dpm, dpc, and is a breathable structure, and the new bit has a dpm, dpc, and isn't, there's perhaps a risk of exacerbating any damp issues in the old part close to the join. I don't know a way around this, but it must be common in old houses that have new extensions, and may not affect the old house too badly.

 

[Feltwell]

A new extension will be fundamentally different to the old house, due to the building regs as much as anything else. You don't need to worry so much about breathability on the new part.

I don't think the fact that the old house has lime will affect how it's done.

Agreed. As your house is quite late, it almost certainly will have a DPC already, which your builders should be able to join to the DPC on the extension. You should be able to see the DPC on your current house if you look carefully - often they are positioned at the same height as the bottom of the airbricks, look for a thicker mortar joint.

If the extension will cut across any airbricks on the house make sure that an alternative airbrick can be installed elsewhere, if you've got suspended timber floors on that part of your house. Don't think if you haven't got suspended timber floors then they must have been replaced - not always the case on a house that late, my 1899 house is part suspended timber and part solid floor and all are original.

Your new structure will have to have cavity walls, if you just let your builder do his thing he may do the brickwork in stretcher bond which will almost certainly be different to the rest of your house, which probably has alternating headers and stretchers in Flemish bond or English bond. You can make them build it so that visually it looks the same as the rest of your house, but specify that upfront to the builder as it is more work for them and involves lots of brick cutting. I did that on my garage - the builder hated me for it but it was all in writing on the spec he quoted on so he was limited in how much he could moan!

Very simple guide here - note there are a huge amount of different types of brick bonds:-

http://www.heidelbergcement.com/uk/...cks/brickwork_details/brick_bond_patterns.htm

As for joining new structure to old, I've never done that so can't offer much advice - except that extensions to a Victorian house are so common that I would have thought that any decent builder should have no problems managing this.

 

[stuart45]

This is one method of tying in new to old.

 

[MatthewC]

This is one method of tying in new to old.

Ask for "Starter packs" in your builders' merchant (I discovered that about four weeks ago).

I am just finishing an extension to my 170 year old stone house. All we were allowed to do was to rebuild the old Victorian brick extension with similar dimensions and finish. I did think about doing it all in breathable lime, but it really wasn't worth the time, cost and hassle, so it is all to modern standards. However, it still has a Welsh slate roof and uses reclaimed imperial bricks (mostly the same ones from the old extension); about 20% more were bought from a local yard and are an excellent match. The pointing is all in lime with local sand to closely match the colour of the pointing in the stone build - make sure you agree on the style of the pointing -the last thing you want is "ribbon"! I think mine is called "weatherstruck".

See http://houseintheenchantedforest.blogspot.com/ for the full story.

Matthew

 

[stuart45]

Very interesting blog Mathew. Looks like a really nice job. I couldn't see the brickwork close enough to tell what type of pointing it is. Weatherstruck is done with a pointing trowel at an angle as the work proceeds. Weatherstruck and cut is similar, but the joints are raked out first and then filled. The bed joints are cut off level with a straight edge and frenchman (bent knife). I would guess yours is the latter as they were pointed later.
Normally the builders would go for a bucket handle finish as this is the easiest. Ribbon is a lot of work, so it's unlikely they would do this as a default finish.

 

[Feltwell]

Ask for "Starter packs" in your builders' merchant (I discovered that about four weeks ago).

Or ask for "Furfix" - it's actually a brand, but much like builders use an "Acro" prop or a "Stanley" knife, it's become a generic term.

They work fine with modern builds, I've seen them used lots of times. I've not seen them used on old buildings, hence my lack of comment above - don't see any reason why they wouldn't work though. They do give a pronounced mortar line at the joint, which I'm not a great fan of.

The traditional way to join an extension in was to "tooth in" to the old brickwork - see the link below. You need to have bricks either the same thickness as your imperial ones, or thinner but with thicker mortar lines in order to do this. It also needs more skill from the brickie to do a good job. The link below illustrates the difference quite well.

http://www.squirrelconstruction.co.uk/house_extension_toothing_in.php

As for pointing, it's personal preference as much as anything and what matches in to your exisiting building. Bucket handle I personally don't like the look of on an old building, but it does have practical advantages and is quick to do. I went for flush but then rubbed over with a stiff brush - not technically the best but it matched the house quite well and, using reclaimed bricks, made the walls look "old" pretty much from the outset.

 

[stuart45]

Years ago we nearly always used to tooth in new work to old. The main problem with this method is that you are stuck using the original brick gauge which may cause a few problems with the frame and cill heights, although you can usually work round this.

 

[MatthewC]

In fact I've just remembered that MdB recently made a good post about the types of pointing http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=12430&p=165444. It turns out I have "bucket handle", which I think is what was there before.

I'd not noticed in the OP that Spot's house is entirely brick - of course, since my (old) extension was brick built up against stone, I don't have an issue in doing the same with the new one using the starter packs. I certainly would want to tooth it in as suggested, if it was all brick, and would also certainly use reclaimed Imperial bricks to match the original.

 

[spot]

Thanks to everyone for the detailed responses. Plenty for me to ponder here!
The one point that still concerns me is just the areas where new brick with modern mortar meets old brick with lime mortar is there a potential for damp getting trapped and if so what's steps should be taken to avoid problems? Or is it just a case of the "contact" area involved is usually small enough not to cause any issues?

Additional info for what it's worth... House is part timber floor with about a 1 meter drop below and air bricks and part solid floor and as far as i'm aware this is original. Also, the house does have cavity walls (which I guess is unusual for one this old).

 

[stuart45]

Because the old house has cavity walls also, the builder will need to either cut out the cavity width in the old brickwork where it meets the new, or cut through the brickwork with a saw and insert a piece of vertical DPC in the wall to prevent possible damp penetration.
There should be no problem where the cement mortar meets the lime, although there may be some settlement in time in the new work which will show at the toothing join.
In the old days they sometimes built the new work a fraction higher to allow for settlement, and filled the beds on the toothings later.