Monday, 10 May 2010

House build begins with Stone and Hydraulic lime

Planning permission finally arrived early May. First off we need to take the adega wall down, insert foundation stones, get it square (full 90 degrees) to the main house (so the roof of both buildings fit together properly). João our stonemason was actually the one to point all this out (architect and engineer didn't seem to notice). Here he is, left, with his new toy doing his thing!

Day1: Wall comes down in bits. João stashes the main big stones strategically, then digs ditch for the foundation stones. No cement foundations here - pedras de Porinno (vast granite lumps, from about 30km away).

Day2. Re-align wall so that it sits at a proper right angle to the main house. Tools used: some string and a bit of right angled metal. Foundation blocks in.

Day 3. Wall starts to go up; first 70cm or so. Site for door chosen. First mixes of hydraulic lime (full strength: NHL5. This stands for natural hydraulic lime by the way. It's not actually pure lime, it has a bunch of clay impurities in it, or baked clay basically. Which means we don't need to add pozzolans. Hmmm, lime needs more discussion than this. Soon).

Day 4. More wall goes up. New window bearer chosen (chunk of granite that the window frame will sit on). Lime mortar going off nicely within 24 hours. Sand - lime mix used was more or less 2.5 sand to 1 lime. Nada mais.

These slabs are the foundation stones. João put them in that trench he had dug and that was that. No faffing with cement foundations and all that.

João thinking. About this window. Used to be a door there. And steps will go on the other side. So it can't be too low. Nor too high...

By day 6 João realised we should maybe have taken out all the rubble from inside first... uh oh. No problem he exlaims, we'll dig it out through the doorway. Within 20cm or so we found nothing but bedrock, so we hired a compressor and drilling thing and hammered away for another 4 or 5 days. Slow, grinding work.

Conrad and his Pa Jon (and daughter Lula) visited during all this, and Jon muscled in there with the rest of them - at 70 and still as strong as the next guy!

So up until today we've been digging down: to around 30cm below eventual floor level so we can fit in all that underfloor stuff. And now we have to learn all about floors - and if we want to avoid cement and plastic (DPC) we have to think carefully. So far we're thinking thus: 1. 8cm small river stones for drainage and capilliary break (so water can't come up). Some kind of geotextile that prevents moisture - if it's somehow made it up past the stones - but allows floor to "breathe". 3. Insulation, maybe cork, maybe 6 to 8cm. 4. Limecrete floor with underfloor heating at about 7cm. 5 final cover, lime and broken tiles, like in Roman times. Which sounds good in the Lime Book.

These photos show how much rock we have to get through...

Mainly, we've been learning about hydraulic lime mortars: how they work, how they don't. We've found the best mix when you mix water and lime first, for 5 mins or so, then add the sand, slowly, and water bit by bit till you get the right consistency.

Sunday, 9 May 2010

Building for Kiwis

We planted three kiwis last year to grow over the outdoor table, to provide summer shade and winter fruit. They hardly grew, we gradually forgot about the prospect of fruit, and ended up using any old screen for shading erected over a bamboo frame, supported on both granite and wooden posts dug into the ground . By Spring, at least one of the wooden posts had started to rot - mould and fungi were starting to appear half way up, inevitable given the amount of water in the ground all winter. Also, by this Spring, the kiwis started to grow again, and they have almost reached head-high.

This issue of using wood close to the ground in building is a classic design fault common all over the world. In 1997 I worked with Movimondo in Guatemala where a part of their community development project involved showing locals how the use of around 70cm of stone footing for their homes would extend the life of the wooden walls, saving them the financial burden of rebuilding their homes every five to ten years.

Here in Portugal, and also in Scotland, I know that people generally believe it's sensible to sink a post deep into the ground, often bedded into cement for "extra strength". We are also advised to paint the end of the post in tar, or burn it first to prevent rottage. But Paulo has introduced the idea of using rocks as the principle footing to ensure the posts stay dry and last many times longer. Small metal bars, around 8mm diameter are inserted into the but of the post, and a similar hole drilled into the rock. This merely holds it in place - it is really wobbly and insecure at this stage. Temporary cross bracing to the ground keeps it from falling down.

Once a few posts are erected, a beam joins them together along the top, with simple lap joints with more metal bar to keep it together. This helps to secure the wobble a bit, but it really starts to get more secure when you link up the posts in both directions and add cross bracing. Rafters helped with stability too.

The posts are made from oak chopped from Donald's forest last year, and the central beam is from chestnut coppiced from around our watermill this winter, shown here. We have taken to removing all the bark to prevent the multitudes of bugs and creepy crawlies that live under there chomping away at the sap wood.

So we decided to build a whole new frame partially using the granite posts that we had but mostly from new oak posts. Photos say rest of the story...

Jon - roped in from Scotland, helps shape some new cross bracing for the central posts (that's him in the nifty hat:)

One of Paulo's lap joints

Chisling in for another

The chestnut beam is placed

Paulo's bird's nest view of us 3 trying to get our heads around more cross-bracing

Someone taking it easy (that'll be Charlie)

Bugui, Galician yoga teacher, going with the flow of debarking.