16th century oak-framed house in Henley on Thames
Rotting original timbers restored for hundreds of years to come
Meet the client...
My period and Listed building repair, restoration and conservation work takes me all over Oxfordshire but one of my favourite projects was located just a stone’s throw from my workshop in Henley on Thames. I met my client, a retired local businessman who lived with his wife in a large 6 bedroom, 16th century oak-framed with brick in-fills house, when he called me concerned about the safety and security of his property. He knew that the main downstairs tie beam that held up much of the back of the property was showing signs of rot and feared the building may totally collapse. I agreed to take a look and see how I could help.
The challenge
Upon some initial investigation and diagnosis work, I found that unfortunately it wasn’t just the main tie beam that was suffering from rot. Over a period of years, the original lime mortar pointing and render had fallen out or just worn away and had been replaced by cement introduced where the original bricks met the oak timbers. Naturally and inevitably, timbers and buildings move over time and where the cement would have come loose, water had got behind the cement and the oak. Unfortunately, cement doesn’t allow anything to breathe so any water or moisture had never dried out causing significant amounts of rot. Lime mortar on the other hand expands, shrinks, and breathes and allows properties to dry out making it ideal for historical and period buildings. My client’s house had not one but five oak-beams that were significantly rotten and in some cases, given they had been rendered over with cement, there was nothing left of the timbers and only the bricks were holding the house up. We agreed I would explore the severity of the problem by opening up the cement and closely inspecting the timbers behind it, to diagnose the problems and see how far back and deep the rot went.
The bottom line...
What I found was that there were two types of problems one of which led to a third complication. The two problems were that:
As my client suspected, the main 6m ground floor oak main tie beam that supported one whole side of the house was rotten. In fact, of the 12” width, 4” of it were entirely rotten. This was significant because the brick in-fill panels were resting on this side of the beam and it held up pretty much the whole back end of the house and approx. 5.5m of it had disintegrated. These 4” needed removing.
Four other beams had also completed deteriorated which whilst smaller beams, were none the less significant because they had been totally cemented across and pointed in making it look like it was bricks but it was all hollow behind it.
The complication was that in order to repair this correctly, two brick in-filled panels would have to completely come down and the house would need to propped up and supported while the repairs made. We agreed I would repair the main 6m tie beam and replace the other 4 beams.
How I solved it...
The main steps we took to successfully complete the project were that we:
Removed all the cement and old lime mortar from the oak timbers and original bricks.
Propped up the two brick in-filled panels on one side of the house, then removed all the rotten timber and any unusable bricks.
Re-installed the original bricks.
Restored or replaced the timbers with new oak and replaced unusable bricks with similar-aged bricks and installed them using lime mortar.
Once the mortar was allowed to dry, we returned a few days later to lime wash all the new repairs. The benefit of this is that is that it will allow the new repairs to breathe as lime paints will allow some moisture to penetrate but will also allow this moisture to escape and for the timbers and bricks to dry out thoroughly.
We also...
The 6m long tie beam needed a few additional steps because of its significance:
To replace the rotten timber with a new oak beam, we first had to prop up the brick in-fills with a steel beams and support the walls with acro props.
We then set about manually chiselling off 4 x 10 inches of rotten timber along approx. 5.5m of the original oak beam.
Next, we took a 5.5m new oak beam, planted and fixed it to the original beam using stainless steel fixings. The replacement oak had leaded windows set into the beam so this had to be manually chiselled out for the windows to be re-installed properly. The new oak was then repointed into place with coarse lime mortar and the fixings were covered over with oak pegs keeping in with the original appearance of the rest of the house.
Once the lime mortar had set, the acro props were removed and we set out repointing the remaining bricks. This was then also finished off a few days later with lime wash just like the other beams we repaired.
The result
The whole building repair took about 3 weeks and we were able to keep any disruption to a minimum because largely the majority of the work could take place outside. There were only minor bits of work to do on the interior of the house which was when we needed to shape and install the oak of a similar age around the leaded windows.
Without these building repairs, my client’s house would have certainly continued to rot and potentially create an unsafe house due to the weight of the house resting on the beams. Now the risk of building collapse in these areas has been minimised, it’s completely resolved and we’ve reduced the risk of any further decay. We left the house is completely secured for at least a couple of hundred years to come.
