The last sill – For our big window

We worked on the sill for our big window in the south wall of the east wing. Two reasons. Firstly it is the last complete opening still missing its sill. Secondly, we cannot finish insulating the east wing until it is done. It is around 3m high and wide and we had left it with the foundation blockwork built up to finished floor level, with tanking membrane laid up the back edge. We decided to leave it as is and to build the sill on top. This will lift the window proper above floor level, reducing the possibility of anyone accidentally running anything directly into the window frame or glazing. In fact, we do not have a sill that is 3m long, we will prepare two of our 1.6m lintels and join them in the middle.

The blockwork at the base is 100mm. This a bit skinny and we wanted to widen it nearer to 200mm. We dug out the ground immediately in front to foundation level and laid concrete above it, to level it up to 200mm below ground. We mortared a second course of blocks in front, to ground level, then faced above it with a thin layer of granite and finally a course of lime mortar above to create a 10-degree slope outwards. Once it had gone off enough, 48 hours or so, we lapped tanking membrane up and over the mortar.

• 

• 

• 

• 

We found two lintels that matched in height and width and processed them as we had our other sills. Propping the sills at a 10-degree angle, we sliced the fronts vertically off with the angle grinder and bush-hammered the faces. Then we cut the undersides at 90 degrees to the front and sliced drip grooves into them. Finally it was a case of slicing them to length, notching either side of the window opening so the ends of the sills slotted into them. We did a dry run installing them, to check the alignment and that they fitted. They lined up well, with a gap of a couple of mm between them. We fitted eight of our chunky steel angle brackets to the blockwork underneath, stuck strips of foam on the base to spread the weight of the sills and put them in place permanently. We used squirty foam underneath the sills then screwed the sills to the angle brackets. And that was it, though we will need to fill the gap between sills, possibly with epoxy resin mixed with stone dust.

• 

• 

• 

• 

• 

Truss preparation – sills

The north wing needs work doing on it before we can put trusses along the length. We have five windows that need sills, three of which also need quoin stones. The latter three currently have two structural lintels only, above the concrete-blocked inner skin. They will need the third concrete lintel once the quoins are in, at which point we can complete the raised wallhead, lay the wallplate, then install the roof trusses over those sections.

Preparation:

1. Pick a granite lintel and choose the flattest surface to be the top, visible, part of the sill
2. Remove the biggest bumps off the bottom surface by a) Laying the sill upside down and cutting grooves with the angle grinder, across all the high points, then b) Using the hammer drill with a chisel tip to break off the ribs of granite
3. Turn the sill right way up and decide which is to be the outward-facing long edge
4. Rest the opposite long edge on a piece of 38mm batten
5. Mark a line along the top of the sill, 18mm in from the facing edge
6. Holding the angle grinder with the disk vertical, cut down along the marked line to the full depth of the blade
7. Trim remaining material from the bottom edge of the cut
8. Use the hammer drill with the bushing head to texture the cut surface, periodically brushing away the dust and re-doing areas that need it
9. Mark a line along the bottom edge of the outside face, roughly 90mm from the top surface
10. Cut along the line with the angle grinder, at 90 degrees to the bush hammered face
11. Lay the sill upside down and cut a v-shaped groove along the cut face, a cm or so in from the edge.
    

    

    

    

    

    

How not to do it: The first sill I cut, I left the bush-hammering almost to last, after I had made the last cut. It is quite brutal and spalled-off chunks of granite from the cut edge, which made it look a bit messy even after it was installed. It did not seem to damage the upper edge, which is greater than 90 degrees, plus it has a distinctly rustic finish anyway.

Installing the sills:  Was exactly as with the three we did in July. We painted the sill area of the window opening with tanking primer, let it go off for an hour, then cut tanking membrane to fit. If the window opening already has quoin stones, we cut grooves 3cm into the stones each side to slide the sill into. We used 5 strips of double-sticky-sided foam trim spread along the length of the sill. If the surface was uneven, we added extra layers to level it up. We rested the sill in place and lined it up until a) it was horizontal along teh long dimension, b) it was in line with the wall face and c) the outside edge of the sill was vertical. We drilled three holes in the back of the sill and screwed on lengths of steel strap, which we screwed down to the back of the window area. Finally we squirted foam underneath, to provide a firmer base for the sill and to waterproof the bottom edge.

Before I forget again

I forgot to post some of the photos Ric took in his last week.

He just about got the east wall finished, but had a mishap with our only pointing trowel, which we use to rake out mortar. So it looks a bit gap-toothy at the moment, we will finish this off when we get up in September and get the raised wallhead blocked out – probably a days work, weather permitting. Meanwhile we are well pleased with how the stonework is turnng out!

One thing that puzzles us: Why is our rubble wall so pale compared to the untouched wall, when it is built from the stone we took out of the walls in the first place? Obviously the mortar is new, but not the stone. Answers on a postcard, please.

He got two more thresholds installed on doors opening onto the courtyard…

dav

dav

He built up stonework to sill height in the last two window openings in the north wing, that started life as doors. So all 5 window openings are ready for sills, quoins and lintels. None of them will have stonework above the lintels.

dav

dav

He heroically got all the openings with blockwork synthaprufed.

dav

dav

dav

dav

He also carried on with his research into how to convert our piles of spoil into graded sand that we can use in our raised drainage mound.

Our first home-grown window opening!

Having got our bathroom window sill in place, I got going on forming the window opening. We had decided a while ago that all three windows on this length of wall would use red Peterhead granite quoins. I levelled up the granite walling to just above sill height, picked my first two quoin stones to match the coursing of the rubble wall and trimmed the corners so that they overlapped the sill by 30mm each side and lined up with the concrete blockwork at the back of the wall. I laid them in lime mortar and pinned them in place. It was quite straightforward to build the quoins up, alternating the direction they lay (along wall, across wall, along wall etc.), four courses each side. The door frame will be set back from the outer wall face by 215mm, less the length of projection of sill over wall face, less the length of overlap of frame onto the back of the sill. This is around 150mm and any gaps behind that we could fill out with concrete block, to save stone. I built back from the quoins to original wall as I went, to stabilise the whole thing.

I left the quoins a day for the mortar to go off enough, then Ric cut the third concrete structural lintel (the other two were already in place supporting the concrete blockwork) and the outer granite lintel and lifted them into place, with a gap between them. I made a wooden framework to fit under the window, wedged it in place then filled the gap with a dryish concrete mix. I tied a luggage strap around the two lintels and wedged a stone in the top between the lintels, to hold everything in place until the concrete set. Which it did by the following morning. And that was our first self-constructed window opening. There are already 5 pre-existing window openings, but it was still a great feeling to do our own!

Our first home-grown window sill!

Getting our granite lintels delivered was quite a turning point for us: We cannot get our roof trusses installed until we rebuild our walls; we cannot rebuild walls without getting windows and doors formed; we cannot form windows and doors without sills; we could not make sills until the lintels arrived. Our building warrant had specified concrete sills – this did not appeal to us at all. Ric convinced us that we could convert lintels into sills without too much effort & cost. So as soon as we got the lintels, Ric got to work. He used the bathroom window, in the east wall of the east wing, to test out his ideas…

1.  He cut a 1.6mx212mmx100mm lintel to the width of the window + 50mm.
2.  The sill has to slope forwards to shed rainwater, Ric used the angle grinder to trim the front face to be vertical once the sill is in place. He used the bush hammer on the sawn front and ends to get a suitably rustic roughened finish.
3. He used a simple wooden jig to guide him using the angle grinder to score irregular lumps on  the base to a level and used the medium breaker with a chisel tip to clean it up.
4. He trimmed the front of the underside to be horizontal once the sill is in place, then cut a groove along the length, as a drip-line.
5. I installed tanking membrane over the base of the window opening. This was laid on a single coat of primer and run down the inside of the wall by a few cm. We need to tank the lower metre of the wall (and 1.5m of floor) before we build the timberwork to hold the wall insulation, we will run the tanking up and overlap onto the window tanking, to make a continuous barrier to water.
6. I used a 6mm double-sticky-sided foam strip to create a cushioned base to lay the sill on. We laid five strips down the sill area, doubled up to 12mm.
7. We placed the sill over the adhesive strips and adjusted it to be horizontal along the length. It had a sensible slope downwards.
8. I cut three lengths of 25mm x 1mm galvanised steel strapping, drilled holes in the back of the sill and into the top of the concrete behind the sill, then screwed the straps in, to stop the sill being able to slide forwards.

And that was it. When we get round to it, we will squirt foam under the sill to seal it and spread the loading on the sticky foam seals – although I was rather surprised that it really did not compress a great deal under the load. The window frame will lap over the back of the sill by a few cm, we have plenty of space behind to run insulation and the window ledge under the rest of the window frame.

Our first door threshold!

Although it was not a priority, Ric found time to experiment with door thresholds, using the external door onto the courtyard from the kitchen area. Like all the other doors onto the courtyard, the opening is original, with quoins already in place. He measured up carefully and trimmed one of our 150mm thick lintels to door width + 50mm. He used the angle grinder, rotary hammer and medium breaker to chisel out grooves at the base of the door opening on both sides. He trimmed the ends of the sill to the width of the grooves, then simply slid the sill into place. The top of the sill is positioned at finished floor level, so the door frame can lap directly onto it. When we get round to it, we will concrete under the sill, then pack any remaining gap with dry sand/cement.

In doing this, we made our final and irreversible decision on floor thickness above the concrete slab! Originally, we were expecting to be pushed for height inside the steading, this is looking to be less of an issue. So we will abandon the idea of the (comparatively expensive) gypsum-based self-levelling screed, which can be as low as 40mm and go for the (comparatively cheap) standard sand/cement screed, minimum depth 65mm. We assumed 70mm, with 15mm for floor covering and the 100mm insulation – 185mm total. There should be a big cost saving for us because we will not need contractors to do the work. It will allow us to screed the floors at our own pace, in particular no penalty for creating the finished floor in sections.

July visit

I was at the steading for a full week in early July, with Ric. The aim was to prepare for our September visit, where we want to get roof trusses up on the east wing and, if practical, part of the north wing.
To summarise where we are with the east wing…

• West wall (facing the courtyard): We rebuilt the doorway and installed lintels over the door and small window in April, then built rubble wall above the lintels to old wallhead height. We still need to lay blockwork to raise the roof to the design height.
• South gable-end: The parapet and retaining stones will need raising to the new roof height but can be done after the trusses go on. At the same time, we need to remove the stub of a concrete lintel that was embedded into the courtyard corner.
• East wall: The pre-existing doorway has been blocked out as a window and we completed the stonework up to sill height back in April. Last Christmas we opened out a section of wall to install two windows. The backing blockwork for one window is complete, the other is not blocked out because we plan to install quoins for a splayed window and do not really know how that will play out. We need to do the stonework (sills, quoins, lintels) for all three windows, complete the backing blockwork, lay the rubble walling, then raise the wallhead to the design height with the four courses of blockwork.
• North gable-end: This needs one side tidying up, replacing missing quoins and the retaining stone (for the coping). The parapet will need raising to the new roof height, but can be done after the trusses go on.

So most of the work on this block translates into:

1. Getting possession of the 41 granite lintels we ordered in March from Lantoom Quarry, Liskeard, Cornwall.
2. Converting three of the lintels into window sills for the three window openings down the east wall of the east wing.
3. Installing the sills, building quoins up the sides of the window openings and placing concrete (structural) and granite (decorative) lintels.
4. Completing the inner skin of concrete blocks up to old wallhead height, where we had demolished original wall.
5. Re-building granite rubble walling in front of the concrete blocks, around and over the window openings, up to old wallhead height.
6. Lay the four courses of concrete blocks above the walling, to raise the roof to the designed height.

Ric was confident we could do it, I was prepared to give it a shot. Being mid-year in northern latitudes, I could allow myself as long working days as I could stand – it gets light at 4am and dark after 10pm!

I brought the strimmer up with me to tame the grass, nettles, docks & thistles, but quickly realised that it was a bit late. The hot, dry weather meant that the perennial weeds had seeded and gone over already and had woody stems – strimming them would be dissatisfying and not very useful.

2018 shopping list

As far as we know, we need to buy the following:

• Granite lintels, cills and thresholds – from Lantoom Quarry
• Around half our concrete structural lintels – Having bought a whole load of 1.5m and 1.8m lengths a year or so ago, we need to get 18 x 1.2m, 8 x 1.5m and 8 x 1.8m ones. We can do this by buying 4 x 3m & 10 x 3.6m lintels and cutting them.
• An initial tonne of NHL 3.5 lime.
• A truckload of sand, probably from the Bridgend quarry near Tipperty, for lime mortar
• A heavy canvas that we can arrange over scaffolding to protect us and the walling from the elements.
• A tarpaulin to cover the sand.
• A truck load of 440 x 215 x 100 concrete blocks
• DPC and other sundries
• Locking castors for our scaffolding so we can run a bay around the concrete slab for working inside.
• A silt trap so we can install our linear drain in front of our garage & front door.
• Blockmix, sand & cement to build a concrete apron in front of the garage up to the linear drain.
• A bilge pump to clear sludge out from our concrete tank

Depending on progress with walls, we may need:

• Structural timber to support roof trusses at each end of the north wing (where we demolished the internal rubble walls)
• Timber for wallplates, truss clips, tie-down straps etc.
• Roof trusses
• Sarking boarding
• Breather membrane and tape (may be a cheap temporary fix to protect the roof, to be replaced when we are ready to slate)

Methinks this will stretch our finances until we can sell our current house and I retire.

Cills & lintels decided!

With the open season for building approaching, weather permitting, we really need to sort out cills & lintels, so we can start building upwards.

We made no progress getting reclaimed granite so will go with Lantoom Quarry, Liskeard, Cornwall. The irony of the cheapest option being at the opposite end of the UK is not lost on us!

What we need
So we have to create 18 windows and 6 doors.

17 windows and all doors need lintels – the large (3m x 3m) window will keep its concrete lintel, which Ric has suggested we can bush hammer to get to a finish consistent with the granite lintels. The lintels for the windows and 5 of the doors will have 215mm high, 100mm deep profiles with 150mm bearing each end. The garage door has a 2.2m span so we are looking at a 300mm high, 150mm deep profile and 200mm bearing each end. Most of the lintels will not be load bearing – the 2 downstairs windows in gable-ends will be, as will 2 doors and 5 in the east/west wing walls which will bear around 1m of wall above them.

All doors, apart from the one for the garage, need thresholds. We will get 215mm deep, 150mm high profiles and will embed them into the openings by 25mm each end, to lock them into the quoin stones.

All 18 windows need cills. We will get 215mm deep, 100mm high profile lengths, again embedded 25mm each end into the quoin stones at each end. The big window we can do as two cills jointed in the middle. In fact, three of the shortest lintels will be off-cuts from the thresholds, so will be 150mm high.

The practicalities are:

1. The garage lintel needs pre-ordering, with a 6-8 week lead time, the rest is stock.
2. Total weight is likely to be between 4 and 5 tonnes, with shipping costed by the pallet/tonne.
3. We will split the order in two. We will get all the granite for cills, thresholds and for those lintels that will be built over first. The lintels for the garage and those for the north wing, (which will not be built over, they will fit at the top of the wall behind the soffits. This should mean we can get going as soon as we get on site.
4. On first calculation, the first batch would be just shy of 3 tonnes, the second batch around 1.5 tonnes.
5. We will need the carrier to unload the lintels at our end!

This all comes at a price – around £4,000. The slight comfort is, this is less than we would have spent locally, for lintels alone.

Alternatives to granite 1 – cast stone
For a bit of due diligence, I looked at prices for cast stone lintels/cills. These are made from crushed stone in a cement binder. My only real objection to them is that they invariably look too clean and perfect, where we want/need a more rustic appearance. There is no problem getting the right colouring and, when weathered, they would probably blend in well enough. We could probably bush hammer them, but…

Without wanting to embarrass them, one manufacturer sells 1.6m non-load-bearing lintels for £136.70 inc VAT against the Lantoom price of £73.03. Another sells them for £52.80. I expect the latter is more typical, some 28% cheaper.

For fairness of comparison, we will need to trim the granite sills, cut out drip lines and finish any cut surfaces. This would be mostly our labour, which we do not cost, but would include some Ric time. So possibly another £1,000 on top of the £1,000 price difference.

Alternative to granite 2 – concrete
Fortunately the architect did not expect us to use concrete outer-facing lintels, if we did, these could be around £58 for a 1.5m length. He did specify concrete sills: A basic 1.2m (4ft) length is around £47, the 1.8m (6ft) length is around £74. On aggregate, this would be a similar saving to cast stone. I am a bit surprised it is as costly as it is.

Next step
Safe to say, using granite is still an easy decision, even with a £2,000 premium. Once we have agreed the details with Lantoom, we will press the button, for a first delivery in early April.

More on lintels and cills

In between getting our Suffolk house in good order, to sell, we are still looking around for Steading lintels and cills.

Finding reclaimed granite is tricky unless you live somewhere close to where it is sold. Decent sized pieces occasionally appear on Gumtree and eBay but invariably need the buyer to collect. It looks as though it would take years to amass material for our 21 openings, plus an out-size one for the garage door.

New granite lintels
So we looked for new granite. We found a few places online and after a good deal of effort, filtered them down to ones we thought were serious. I tended to not bother with the ones that mostly sell granite worktops, so I came across Caledonian Stone and thought no more of them. I found a place on eBay that sold new kerbstones that might have done for cills, but were on the thin side. We discovered Lantoom Quarry, Liskeard, Cornwall. They have a good range of split-face lintels in three different colours and they publish their prices. Ric had bought from them and trusted them, but we wondered whether there was somewhere with similar prices but more local. We were not making much headway, so I revisited some of the earlier prospects. I looked again at Caledonian Stone and was surprised that they are based in Peterhead, just up the road from us.

They have a smartish website with a chat feature, I gave it a go and got contact details for someone who could give us technical information. He replied quickly, they do indeed do 2500mm and 3000mm lintels in grey granite. They are 290mm x 100mm profile in a range of finishes. They are priced between £250 and £300 each + VAT. I worked out that we would need 18 lintels (excluding one for the garage door,) the bill would be over £4,500.

I checked back with Lantoom and was almost shocked to find that 2100mm and 2400mm lintels were between £50 – £65 + VAT. We would need 21 lintels excluding one for the garage door, the bill would be no more than £1,400. Ric checked directly with the quarry on delivery costs. The lintels would weigh about 4 tonnes and cost £400-£600 + VAT to transport. Still around £2,000 for the lot, less than half the price of the local supplier. We might look at Caledonian Stone for their 3000mm x 290mm x 100mm lintel, for the garage.

The good news is that the lintels are stock items, we can order them once we are at the steading in April.

The garage door lintel
Which led us to ponder on how we would incorporate such a long lintel into the gable-end wall, without damaging it and risking the wall above not being supported properly. Suppliers are reluctant to give safe loading data, which is probably very variable for what is, after all, a natural product. After a quick Google, we found a simple calculation to estimate breaking load for stone lintels:

Breaking load = 2 x breadth x depth x depth x modulus(of granite) / length

They conveniently gave a modulus value for granite. We had to convert to Imperial units and convert the answer back to Kg – the breaking load would be approx. 5900kg. The same website gave us a working assumption that the safe static load would be 1/6th of the breaking load, approx. 980kg.

This is nowhere near enough on its own, however we looked last September at a Catnic box beam with supporting shelf, which, with a second one behind it supporting the concrete blocks, would easily be strong enough. The downside being that we would see the supporting shelf from below. Lantoom quarry suggested that the granite lintel could be self-supporting i.e. placed directly on padstones on the wall either side. We would place a Catnic directly above the lintel and push mortar in the gap between them. The Catnic would bear the weight of the wall above.

Ric suggested DPC between lintel and Catnic, then lifted up behind a couple of courses onto the inner leaf of blockwork. Any water that ran down within the wall would run out over the edge of the lintel, not behind it.

Cills
I am following a prospect for reclaimed granite kerbing to use as cills, but am not getting much of a response. We will give it a bit longer, then look at what Lantoom Quarry have. Ric suggests getting cills that are 50mm wider than the window openings and lintels that are 300mm wider. This would give us more scope for cutting longer pieces of granite in two, reducing costs significantly. He is asking Lantoom Quarry about 300mm x 150mm profile granite to see if that would be suitable.