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Cavity Walls to First Floor Level

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Laying the Concrete Slab

We’ve all heard that saying about how a good professional makes the job look easy. Well that certainly applies here. If you’ve ever tried laying bricks or blocks, you’ll know how time consuming it can be to get your levels right and keep the whole thing level, vertical and straight. These guys make it look like a breeze. Of course it’s not - it just looks that way.

A couple of pallets of reclaimed bricks have arrived and these are ‘blended’ with those salvaged from the original extension. Doing this, as Dale from G L Smith explains, ensures that the final result has a uniform appearance and it all ties in well with the original house. Stacks of bricks and blocks are set out round the perimeter of the new walls so that they’re always within reach, and spot boards for the mortar are set up at intervals too.

Stepped lead and damp proof course A damp proof course is laid on top of both the leaves of the existing brickwork. Then the corners of the outer brick skin of the cavity wall for the extension are built up. These stepped leads as they are called act as a guide for the brick courses running between them so getting them spot on is essential. Lines of mortar are thrown and the bricks are bedded into it with great precision. A spirit level is in constant use as the corners go up, making sure they are spot on.

Pointing the reclaimed bricks Pointing is carried out as the work proceeds. The finish is weatherstruck meaning that the top of the mortar is slightly recessed and the bottom slightly proud. The joints are smoothed with a pointing trowel and finally, the brickwork is lightly brushed with a broom head. The net result blends in very nicely with the existing house.

Once the stepped leads have been built up, a builders line is drawn between and fastened at each end. The line is carefully set on the top corner of the next brick course at each end and acts as a guide for the level and line of the next row of bricks to be laid.

Flemish bond brick work Cutting reclaimed bricks

The work is a little more complicated than a standard wall of stretchers. The original house brickwork is in Flemish bond so the extension needs to match. Flemish bond as you can see in the pictures comprises stretchers and headers laid alternately. Walls in the past used to be solid brick so laying Flemish bond didn’t require masses of cuts. Nowadays though, with a cavity wall construction, each of the ‘headers’ is in fact only half a brick so there are plenty of cuts needed. One of the bricklayers was preparing these earlier. Reclaimed bricks can be a little fragile but fortunately there wasn’t too much waste. A light marking with a bolster and hammer followed by a sharp tap on the same line on the face of the brick was all that was needed.

Brick ties inserted Channel with twist and slide ties

As the outer skin progresses, brick ties are inserted at regular intervals. Where the brickwork meets the original house, a brick tie channel with twist and slide ties has already been anchored to the wall. This provides a good method for tying the brickwork together without having to tooth out the original brickwork.

Block work and insulation Block work being levelled

With the outer skin well under way, the cavity insulation and inner block work skin can start. The insulation is positioned against the brickwork before the blocks are laid. Stepped leads of block work are then built in much the same fashion as for the brickwork. In the same way as before, a builders line is drawn between the block corners and the full courses are laid.

Ground floor block and brick complete Ground floor block and brick complete

With both skins up to first floor level a scaffold will need to be erected so that the next lift can be built.

If you live in the Hertfordshire area and are looking for a professional building contractor, you can get in touch with G L Smith and Sons via their website:

Previous Stage
Laying the Concrete Slab

G L Smith and Sons