Good Lord - it's 17 days since the last blog. In my defence I would like to point out that not very much has happened. We have been much exercised by wall structure. To explain the options, here is a request for information which I posted on the website of the very excellent AECB:


"Gold standard walls – the best construction

We are self-building an 11.5m x 9.5m two storey house in East Anglia. we want to build a zero heating house (woodburners for winter backup). We are currently working on a 540mm finished wall thickness. Exterior rendered. Thermal mass if possible. Reasonably tight budget. Concern about interstitial condensation.

We have looked at a number of wall systems, as follows with potential problems for each one:

1. Hemcrete – no problems except cost. Zurich will guarantee but only as an infill material so a complete structural timber frame is also needed. Double that for price of 500mm (installed) Hemcrete and add cost of erection and external render.

2. Double skin of blockwork with 300mm cavity filled with Rockwool. Dense concrete gives better thermal mass so possibly dense inner skin and aircrete outer. Ties have to be found – 450m. Zurich approve as long as ties are okay. BedZED had own ties made. Problem with large amount of embedded energy. Also difficulties around window and door reveals (no problem there with Hemcrete) and very dependent on good craftsmanship to avoid cold bridging and leakage. Construction may be slow. Rain ingress into cavity during construction. Seems a lot of bother. Why bother with external skin of blockwork at all?

3. Timber frame with 300mm studs – possibly Masonite or similar. Major problem is that we do not like the hollow sound of dry-lined walls. Would cellulose filling eliminate this? Or maybe Rockwool for weight.? How could we get to c. 0.1 u-value with rendered surface and no cavity (no point in extra skin of expensive purely decorative blockwork).

4. Clay perforated blocks with woodwool external insulation – seem like a good idea but expensive and may not achieve the u-values for a zero heating house.

5. Hybrid masonry / TF systems. We discovered these last night on this forum. How well tested is it? Which goes up first? Which is structural. The idea of building to the FF and tying it all together before going up sounds good as about one-third of our FF is in the roof so we have large gable ends.

6. Or – could we put up a thick masonry wall and insulate it externally? Window reveals would be set a long way in? How would the roof/wall connection work?

In every case – what about interstitial condensation?

Your help would be much appreciated. Otherwise going mad with too much information."


Anyway I got a private reply from their technical manager who referred us to the Passivhaus UK office. This is a standard which has been much used in Europe and is now coming to Britain, sponsored by the equally excellent Building Research Establishment. So hopefully after much floundering in the mud we are getting the advice we need.

Not too much literal floundering yet. We have four groundworkers giving us quotations for the foundations - more about that next time. We also have a muhurta or auspicious time for groundbreaking and putting in a foundation stone, which is the 28th April. That should give us time to decide what we want to build!!

In the meantime we are demolishing the garage and here are shots of both of us ruthlessly pulling off tiles. Bargain of the week was this scaffolding tower from Jewsons for £25.50 for the week. We'll need all that time. Roofs are much bigger and heavier, when you actually get up there, than you think they are going to be.

In the meantime the caravan is very spacious. cosy and convenient - The Girls came for Mother's Day and E said that we needn't bother building a house - she liked the van. A good thought and it does face due East (R chained it down).

Anyway, a few pics of the demolition. Check the cute red hat. (R did have a hardhat on for most of the time - he was sitting astride the ridge in a very dashing way for most of the day.)