A milestone of sorts has been reached – as the cottage has its new roof, temporary windows and is effectively weather tight. We can take the scaffold lid off. The scaffold company wanted the roof for another job anyway! Whilst it was sad to see the protection go, the new roof and chimney can now be fully appreciated – as can the estuary views!
The external cladding of the cottage proved very satisfying. After going backwards for what seemed like an age, the positive work of putting the cottage back together again was very pleasing, though not without its challenges.
Given the added exterior structure boards and insulation, fixing the slender corner posts back to the frame within posed a little design conundrum – nothing that a good carpenter, some sound new timber and long screws couldn’t fix though! The new corner posts are fashioned from iroko, the sectional detail being cut to replicate the original.
The photograph above illustrates (apart from a happy carpenter) the ventilated void behind the cladding. This void is required to be open to the atmosphere top and bottom so as to permit free air flow and the drying of the air space within should any water penetrate the cladding. This void is closed with insect mesh at the top and bottom, to prevent little beasties from making an unwanted home for themselves. The gable ends presented a challenge though. I did not want to see any propriety / off-the-shelf wall vents intruding into the cladding. There are any number on the market and they all look horrible! They are also a potential source of water ingress and thus future rot. An alternative had to be found. After a lot of chin-wagging and teeth sucking we alighted upon the very elegant solution illustrated in the photos below. The slot vents in the thick edge of one of the apex boards, closed with insect mesh, has proved to be a very successful detail. It is possible to feel the convection draught exiting the facade on hot days, so the void and vent are working exactly as they should.
Having primed all the larch feather edge boards, these were brought to site in batches for cutting and fixing. This was a big job and required methodical working. The walls were first prepared by the application all over of a vapour control membrane, taped and fixed to the high density wood fibre insulation below. Vertical battens were then screwed in place, fixed through to the frame below. Careful detailing was required for the positioning and fixing of the corner posts. The sash window box frames, previously primed and painted with their finished coat, were brought to site and fixed into the frame.
Each of the external cladding boards had to be measured and cut so as to start and finish in a position corresponding with the supporting battens below. A level datum was established around the base of the cottage covering the sole-plate. Each board was prepared with a thick coating of end-grain sealer to its cut ends, then nailed at every batten. The end fixings were screwed to avoid splitting the feather edge. Where boards did not fit tight to the board below, the occasional nail was fired through the thick-edge of the board and later filled. Where boards abut the corner posts and window frames, a mastic weather seal was provided.
The task of priming the exterior weather boarding was carried out off-site. It was a huge task, roller application of paint to both sides of each 4m plank, with a second application to the outer face and edges. So there was a good reason for my talented son Dominic’s 1st Class degree from St Martins!
The replacement timber cladding was a big job! 1,200 linear metres of freshly sawn Siberian larch was delivered (from Somerset https://co2timber.co.uk/) to a nearby empty shop we’re using as storage and preparation facility. The feather-edge timber needed its visible surface sanding to take off the rougher saw marks ahead of being primed and fixed to the building.
The priming of the timber was a mammoth exercise, both sides of the planks had to be primed, with the external face being primed with a second coat before getting its finishing top-coats once installed upon the building. We made use of a water based micro-porous paint from Mighton Ankerstuy https://www.mightonproducts.com/products/paints-wood-repair/joinery-paints/exterior. Ankerstuy are a dutch company based in Gorredijk in Friesland. Their high quality water based exterior paints are designed for all applications including exterior cladding in hostile marine environments. Their unique products have been developed for excellent performance, durability and longevity characteristics when used on exterior timber – just what we need.
As you may recall, one of the first things to be done after works commenced and the scaffold was erected, was to remove the old heavy concrete tiles from the roof. These were doing the structural capacity of the frame no good and furthermore, they detracted significantly from the aesthetic quality and potential of the building. The replacement was to be natural slate, just as the original would of been. Not Welsh slate though, it’s far too expensive. Instead, I’ve plumped for a good quality Spanish natural slate. The finished roof looks magnificent – many thanks to Mark Swift and his team at Swift Roofing (swiftroofingessex.co.uk)
You may have noticed that things might be moving very fast given the time between recent postings! I’m sorry to say I’m playing very fast catch-up. The truth is I’ve been incredibly busy putting the building to rights, so much so I’ve been rather tardy in keeping these up-dates going. Sorry!
Anyway, the exterior wall and roof insulation was a dream to install. The tongue and groove high density wood fibre boards slotted together easily and were then secured by long screws through to the frame below. We had been careful to mark the position of the frames on the structure board over which the exterior insulation was being fitted. We cut the window openings out afterwards. The sound deadening quality of this product is amazing!
After the structural support given to the frame by the base layer of Elka Strongboard, an exterior “skin” of dense timber fibreboard was fixed through to the frames, 60mm to the walls and 100mm on the roof. For advice and supply I’ve been making use of a brilliant company in Devon called “Back to Earth” https://www.backtoearth.co.uk/about-us/ and Chris Brookman there gives a very helpful introductory video on their site to explain the company ethos. It chimed with everything I’m trying to achieve here on Leigh Hill.
The insulation we chose from Back to Earth was:
UdiTOP wood fibre insulation sarking boards, these are:-
- a wet process wood fibre board which is brilliant for keeping you warm and dry in winter.
- high density and so great for summer heat shielding, keeping your home cool.
- the best way to form a warm roof which is completely vapour permeable.
- quick to form a weather-tight, bat friendly covering without using membranes/felt.
- ideal for use in noisy or urban areas where their acoustic insulation really helps.
The sustainable, breathable and recyclable nature of the product attracted me, not a sign of plastic anywhere and though heavier is comparable in terms of thermal performance to modern synthetic forms of insulation. Its acoustic noise-deadening qualities are amazing!
The repaired frame needs more bracing than the original carpenters provided. Such bracing as there was was insufficient to arrest the gentle movement down the hill and more recently, the lunge towards the new car park in Bell Sands below the site. A rigid racking board was needed that provided both strength and qualities of vapour permeability, something conventional OSB boards are not especially good for. I alighted upon Elka Strongboard
The framed walls were sheathed in these boards, some 2500 screws securing them to the frame – the timbers having first been carefully de-nailed.
Earlier in this blog I illustrated the parlous condition of the chimney above roof level. We had to bite-the-bullet, carefully dismantle it and then rebuild it brick by brick. The result is fantastic. The use of all the original bricks and brushed lime mortar, together with the help of a skilled craftsman means the cottage has a crown to be proud of! I’ve also managed to secure two salvaged chimney pots to make up for the pair that were lost, probably around 1950. The urgently required essential repair is magnificent. The last photograph below shows the new slate roof, this is to be the subject of a separate post.