Thursday, 14 April 2011

Early Blockwork

We had the block and beam in place with a concrete screed, the drains were in and so the next stage was to start the internal block work followed by the outer skin of brick. 
Having been to the Homebuilding and Renovation show at the NEC and come across the 'Thin Joint Method' of block work and being suitably impressed by its ease of use we decided to employ this method in our build. One of the main advantages being that I could lay blocks well ahead of the brickies as the ties are inserted into the block rather than in the mortar course. A SDS drill,(a cheap model £45 from Axminster Tools) is used with a special tool to drive in the stainless ties at every sixth brick course as one builds the outer course.
This system is a little unforgiving of sloppy workmanship as it is essential that the first course of blocks has to be layed on mortar and has to be dead plumb and level across the block. The thin bed joint is only 3mm thick and there is very little room for adjustment as the wall rises.So that was the first job, a single course all around the build including internal walls as these were block work too.

The first of the Celcon Aircrete Blocks arrives on site

Celcon and no doubt Thermalite supply all the tools necessary to do 'Thin Joint Blockwork' and they consist of a scoop (for laying on the mortar) a coarse sanding block for adjusting the odd block and a very coarse rasp for removing large amounts of block if you do go wrong. Block hand saws are readily available from builders merchants(they don't last long, we used four on this build) and the one part mortar is also readily available. The mortar is mixed in a bucket with a whisk. It is only necessary to mix small amounts (1/2 a bucketful will lay about 15 blocks) as the mixture goes off pretty quick and once layed is bonded to the blocks in less than 1/2 hour. As in all block work joint bed reinforcement should be used every third course and especially around openings, but the manufacturers literature gives guidance on all these issues. We purchased our stainless ties and expanded joint bed reinforcement from Tackburn Ltd.

First couple of courses of block work in place

The technique is fairly straightforward as you can see here where I am using the scoop to butter the end of a block. The bed has been prepared with a layer of mortar next to the door. The system is very quick and requires no great skill, just follow traditional procedures for raising a wall, corners first,then builders line between to give a straight and level line.One drawback to this system applies when lintols or other non aircrete block elements are to be incorporated into a wall. In this case resorting to conventional mortar is required for bedding and making up as these elements do not meet the very close tolerances of the blocks.

Sawing Blocks is simple, but the square(orange) also supplied by Celcon was not very accurate.

Preparing frames for openings.

The block work rises to first floor level without any bricks being laid.

These were extra wide aircrete blocks used down the centre of the build where a structural  wall was required.

A good cup of tea and a biscuit helps the job along

The block work was nearly up to first floor level and by this time I had chosen to lay the first courses of brickwork up to DPC level.  Then one ill fated day after long deliberation I decided that I would carry on and lay all the bricks for the house!!!! It was a difficult decision, I knew I could lay bricks but not at the pace of a good brickie, actually at most 150 a day, but both my wife and I are control freaks and perfectionists so it was inevitable really!

Next time in my blog I will show you how we did some of the brickwork, especially around the windows and the garage doors.

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