Case StudiesThis Old House

The clue was in the name I suppose…The Old House!!

 

We hadn’t owned a listed building before, but 13years ago we decided to dive right into the deep end. A few years and a lot of £££ later, we are now well versed in historic building techniques. And we know first hand the obligations for the owners of a listed building. In all honesty, after 30 years renovating period properties, we were not unduly phased by The Old House. But, this has certainly been our biggest building challenge to date.

 

Actually, most historic building techniques are pretty simple. BUT, the skills and materials’ supply chains have been consigned to history. So, most modern builders deem it to be “specialist”.

 

When planning a barn refurbishment at The Old House, we did get approached by a web-based “find a builder” site. I thought I would test the market, so to speak. I offered numerous explanations about the need for traditional “breathable” building techniques. In return, I was bombarded by builders who wanted to pour concrete and install plasterboard. Neither of these materials is compatible with ancient buildings. In the end, I had to simplify the explanation…

 

You can quote for this building project…but…you cannot use ANY cement!

 

This created a very clear understanding with the potential builders. But it also seemed to whittle the numbers back down to Zero. So I thought really, how hard can this be?

 

7 years later, our Castle Acre custodians (myself included) know how to mix and manage lime mortars and plasters. We also understand the basics of green oak structures. And we have embraced a key fact: Old timber structures must breathe!

 

You hear this phrase a lot so let me explain…

 

Cement was not widely used until the late 1800s. Before then, it was lime all the way! In fact, just about every castle throughout Europe is held together with lime mortar. So shall we dispel the myth that lime is soft?!

 

Anyway, cement was is faster setting and time is the main driver of cost in building. So, from the start of the 20th-century cement was phased in at the expense of lime mortars. But cement – in modern building techniques – is very different to Lime. Cement products and modern DPCs are used to create a waterproof barrier. The aim here is to seal buildings from all that nasty damp and humidity out there.

 

In the Old House, the main supporting timber structure at one corner had succumbed to a 2-inch layer of cement. This was probably installed in the early 20th Century.  This cement jacket was installed to help “prevent” rising damp. It covered the horizontal wall plate and a large proportion of a 12 inch thick vertical supporting timber. These timbers were installed in the 16th Century. They were probably salvaged from British naval ships from the south coast. This makes them even older than the period property itself. Yet they had been propping the house up for 400 years. Simple but bloody strong…sort of fossilized in fact.

 

– As an aside here. I always carry out a test with any new custodians. I ask them to put a nail or even a screw into one of the old house old timbers. This is the first lesson in the properties of ancient oak. A nail has no chance; it will bend or bounce out. A screw…you must be kidding. You’ll end up with a snapped screw or sprained wrist (Don’t worry, I’m not really this cruel to any of our custodians). Ancient oak behaves like cast iron. Fixing something into it involves serious metal drill bits or industrial grade equipment. –

 

Anyway, back to my super sturdy oak structure. It had been safe for 400 years breathing. Lime and plaster allowed air and humidity to pass through, keeping the timber healthy, ventilated and strong. Then along came cement to seal off this ventilation…

 

When I eventually raised the nerve to peel off the cement curtain from this base, the result…compost! In other words, the naturally occurring humidity could no longer escape. It entered the timber and rotted it in a cement tomb!

 

I have subsequently removed all traces of cement. I have installed a new oak wall plate, albeit at a raised height, where the supporting post had rotted away.

 

So these are the perils of cement and sealant when dealing with oak and timber. It’s the same for floors too. When you step into that charming Sussex pub (and we have many), you see beautiful natural stone floors. Are these floors damp? No. Do they look good and work well? Yes. So what damp proof course do they have underneath to ensure this performance? Surely a minimum of 150mm concrete plus DPC? Or are they just laid on a scattering of ash and fine shingle? Yes, you guessed it, its the ash. But a word of warning here – don’t place any rubber backed mats or rugs onto this floor. It is continuously breathing and venting that humidity to prevent damp from occurring.

 

I am rather proud of our latest repair to the Old Stable. Years of neglect and worse many efforts at repointing with cement. As the “before” picture shows, this traps moisture inside the brick. This then expands on freezing and eventually shatters the brick. I had to replace many of these as part of the restoration. Fortunately, the section above 6 ft high was never touched and remains in almost mint condition.

 

Before – you can see the cracked and crumbling bricks. A result of ‘filling the gaps’ with cement

 

During

 

After – the finished product

 

The Mix

1 sharp sand to 2 plastering sand to 1 (hydraulic) lime. dampness and setting times vary and are critical as the process includes:

  • Strip out all old mortar and cement repairs to a depth of 30mm
  • Soak well
  • Apply mortar mix by hand, pushing well into joints
  • When the mortar starts to set (1hr) use pointing trowels to remove surplus
  • When mortar nearly set (2-4 hrs) use trowels again to remove surplus mortar from joints
  • Also, use soft brushes to remove surplus mortar
  • Light spray to keep area damp over 48 hrs
  • Next morning, harder brushes up to and including soft wire brush to remove surplus mortar from edges. Once this really sets it will be very difficult to remove
  • After 48 hrs use a light acid wash to do a final clean of bricks and remove any surplus mortar residue

Or, get in touch with Castle Acre, and we can provide all the tools, skills and expertise to get the job done perfectly.

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