After focusing on a new timber framed extension for so long, we’re now back to repairing the old building. Weak bits of of a rough cement render have been dropping off the front wall, as the picture shows. The cement is just a thin layer skimmed a few decades ago onto clay daub.
We’ve been expecting this, but took a decision early on to let it happen by natural weathering, and then patch repair bit by bit. Looking at the evidence of what’s there, we think patching is the way the walls have been maintained for a very long time – any weakness, then they just slapped on a bit of clay and limewashed it, and owners only recently took to adding cement as well. Continue reading “Back to daub”
I gather that there is questioning among some East Anglian lime specialists of the claim reported in the previous post that traditional hair mixes are significantly prone to failure.
As I mentioned, this is not about the well known deterioration of hair if it is left too long in a wet mix before being used, but about intrinsic faults in the hair, especially if it is imported. Continue reading “PS on lime”
I have to admit now that I have been a bit nervous about our new chalk lime plaster since last August, though I haven’t confessed it so far to the blog: we used imported pigs hair for the plaster in 2013, and more than a year after it was done I was speaking to another lime specialist who gave a deep intake of breath, frowned, and asked: has it fallen off yet? He seemed to relish recounting the story of another Suffolk house where the pig hair had disintegrated and the plaster coat had failed in the first year, on his version of the story because it had a foreign bug that had eaten it.
I’m now much more confident that our pig hair plaster is OK. There are no signs of failure, and from time to time over the autumn I pulled out a bit of hair near the surface and checked it for strength. I tried again this morning and the hair was as strong as ever. Continue reading “Lime developments”
One of the conditions for listed building consent was that the colour of the extension must match the yellow ochre limewash of the old building, so the simplest way to do that would be to use the same limewash mix again. Hollins, the architects, instead specified Keim in the listed building consent application, a mineral paint which has been on the market for well over 100 years, and was developed in Bavaria as a more durable substitute for limewash. I’d never heard of it before, but a web search shows it is widely known.
We’re using lime plaster to finish the outside walls. Lime is a fairly recent revival as a building material, and people are re-learning the old trades as they go, so there are still a lot of disagreements about the best way to do things. It’s not yet Lime Wars, but there are regular skirmishes.
As we’ve noted before, the Essex way (as taught on a course we attended near Braintree) was to use lime and sand as a hard render on the outside of a wattle and daub house. We repaired a wall like that, only to be told off a year later by a local Suffolk expert: the true vernacular coating in Suffolk was a plaster made from chalk, hair and lime, which is tougher and more flexible. Continue reading “Back to tradition – lime plaster”
The more I look at the way our modern extension is being built, the more I am convinced that it is a fitting companion to the original 16th century oak-framed house. There is not a great deal of difference between the basic structural concepts, and only the materials and methods of fixing are new.
The biggest difference is that an old oak frame is mortised and tenoned rigidly with a few very heavy timbers while a modern softwood frame uses more but lighter timbers fixed with nails and steel hangers, and plywood sheets to increase rigidity. A modern construction can also use some big timbers, eg our glulam roof beam which runs the length of the building.
The extension is a conventional modern timber-frame building. First, a wood frame was constructed piece by piece by Terry Booty of Booty Builders and his team, Andrew and Tim, on a low brick base; then they filled the spaces between the timbers with blocks of Celotex insulation, today’s equivalent of the hazel sticks and clay daub that fill in the panels of the old house.
After several redesigns, the engineers settled on a system of 12 piles and a reinforced slab. It was a bit of a saga getting to that point, because although we are next to a pond, there was nevertheless more water in the trial borehole than the experts expected.
The initial plan by the contractors was to auger the piles, to avoid using a pile driver near an old building. However, this was vulnerable to water inflows, which proved excessive, which would have made it hard to be sure the concrete would set properly.
So we were advised to switch to steel-cased piles, with the first three metres augered. With hammered piling starting three metres below ground, it was hoped that the vibrations in the old house would be reduced. This proved the case, though we checked the house carefully every hour or so to make sure there was no damage. Continue reading “Foundations”
Early on, we filled panels where the clay had disappeared with new wattle and daub. This year we have switched to a new plan: these panels, which had been filled in the last 30 years with Thermalite blocks and broken bricks, have been made into a breathable hemp sandwich.
We lined the outside of the building with Savalit woodwool boards (as described before), then plastered them with haired chalk and lime mix bought from Anglia Lime. We used battens to fix Savalit boards on the inside, recessed just enough to take the plaster, and gave them a thinner layer of chalk and lime plaster, also with hair. In fact, internally, Savalit boards can take an extremely thin, almost skim coat of haired lime plaster and still look good.
When the cement was removed, we found some repairs were needed for the timber frame, including a new stud where an old one had disappeared (judging by the empty mortice), completing another stud that had rotted away for the first foot above its mortice in the sole plate, a knee to reinforce the joint between a main internal beam and a post, and a strengthening of one of the corners, where a sound main corner post did not seem very well tied in to the sole plate. It was reinforced with a flexible glass fibre rod through the timbers and a steel plate. All the timber work was carried out by William Clement Smith. Continue reading “Oak and other problems under the old render”
Repairs on a building this age are never really finished, but there is a list of essential jobs we want to do before starting on the extension, for which we won planning permission in late 2012. The first step is to finish the external repairs to the end of the old building where the extension will be built. This means removing a large amount of cement render. Continue reading “Removing cement render – 2013”
We have a great resource in the pond, which we knew about from when we drained it in 2011, but we had not appreciated until this year its amazing building material potential: pale blue-grey boulder clay, which underlies much of Suffolk. Continue reading “Wonderful clay”
Looking around a typical Suffolk village, houses repaired with lime are still quite rare. It is clear that many homeowners and builders have yet to be persuaded of the vital importance of breathability and the use of traditional materials on an ancient structure. There is clearly a huge backlog of work to be done and, judging by the stories we hear from time to time about the terrible problems found in buildings that were repaired thoughtlessly in the 20th century, the damage is mounting right across East Anglia’s huge stock of historic houses.
There is a problem, however, when you start digging into the detail. Even among the experts in these old techniques, there is plenty of disagreement, and sometimes it gets quite heated. As experience grows again, after decades in which some skills were in danger of being lost, ideas are bound to evolve further.
So rather than try to pass on definitive advice, these posts have been setting out some of the techniques we used – or hired experts to use – and we also note where our own ideas and the advice from experts have changed over time, for example our decision to switch from the sand and lime render we used in the first year of the project to chalk and lime plaster for later phases.
More generally, it is important to read and discuss, to take advice from more than one source and to think through the jobs yourself with an open mind, focusing on the particular characteristics of the building concerned. The key points are:
always protect old material, and never do anything to it that isn’t reversible
in the case of infills and coatings, never put in anything that isn’t breathable.
and of course, put some effort into learning about the techniques you decide to use (or hire contractors to use for you).
The remaining pond mud, piled in the garden – perhaps 80 tons – was removed and used for landscaping adjustments, and grass was laid.
The well was properly capped with a steel cover, screwed down, on which limestone slabs were relaid.
A steel structure was built by the same people to make loft access safer.
A brick and stone patio was constructed outside the kitchen with a channel for the power supply and hose of an electric pump for topping up the pond. The flow rates were tested. At the worst of the 2011- 2012 drought, when the well was at the lowest level we have recorded, it produced more than 2 cubic metres of water a day which would be adequate to top up the pond in a summer drought. At other times its productivity was much higher.
The shallow trench round part of the house, which had been dug roughly to prevent damp earth lying against the brick footings above the inside floor level, was redone more carefully. A low brick retaining wall was built, the bottom of the trench the was lined with geotextile, and several inches of gravel placed on top. It stopped the damp coming through the lower bricks and discolouring the limewash on the inside of the brick footings.
Felix Oliver, our next door neighbour, replaced the old stairs with a new oak staircase to a similar pattern but much better finished. The design was negotiated with, and approved by, building control. The result has been widely admired. It fits perfectly at the top to a very uneven sloping floor. Felix is a professional wooden boatbuilder as well as a specialist in oak-framed buildings – see this link to Suffolk Timber Frame Buildings – and his boatbuilding skills show. He also installed 3 new oak studs to replace the rather agricultural – and recent – softwood posts that had been there before.
Insulation was put in the roof above the north bedroom, bathroom and landing, but only on the flat surfaces – the side sloping surfaces were too difficult to access. Part of the the loft area was then floored so it could be used for storage. We discovered that modern polystyrene insulation had been laid under the tiles of the roof when it was redone about 30 years ago and it seems to be intact. There is still a substantial airgap round the rafters, which is reassuring.
The south and east walls were limewashed, pending full re-rendering. All the external window surfaces were oiled with linseed. We couldn’t decide what colour to paint them and linseed oil seems a very good wood preservative and water repellent, so we may just keep coating them for a year or two.
The pond was cleared, removing hundreds of tons of mud, using it to landscape the garden and shrink the overall size of the pond back to where it probably was before the banks were broken down – see the blogroll link to the pond blog for all the details. This took from July to nearly the end of the year so very little was done on the house during this time.