Walls up to DPC

Now all the ground works have been completed we can turn our attention to moving upwards. The first step for this is to complete the walls up to the damp proof course.

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Some considerable thought was given to how we were best going to get the walls from the foundation up to the DPC level.

The drawing on the left shows our eventual solution (the orange object shows the arrangement for the underfloor ventilation). The two lines for "top of oversite" reflect the fact that our foundation has a slight slope and so the amount of void under the floor differs at each end. This will still be a minimum of 330mm though, which is double the 150mm specified in the building regulations.

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The walls were to start with two courses of foundation blocks and these can been seen here having been moved to the area required.

It is starting to look more like a building site now.

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Then it was out with the tape measures and string line to set out the blocks.

Measuring in 4m from the end of the existing building and placing the first block there a '3,4,5' triangle was then marked out and extended to 4.5m to place the first external corner.

Measuring 4.5m off the existing wall at intervals gave us a guide to extend that rear face of the extension wall and 12.5 metres from the first corner, the second one was placed.

Measuring 12.5m along the face of the existing wall then located the final corner. A quick re-measure and we were happy that our corners were square and our walls parallel.

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After starting up the cement mixer these initial corners were laid.

These will be left to go off over the weekend and then the gaps will be filled in.

You'll notice that two of the drains go through these walls, we'll need to place lintels over those as we go.

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Here some progress has been made on the walls.

You can see the lintels in place over the drain pipe.

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And looking back towards the other corner.

The walls for the garage area can be seen on the 'Garage floor' page.

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This is a picture of one of the telescopic vents having been placed and mortared in to stop it moving.

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And this is it from the other side showing how the inside looks once the inner block leaf of the wall is in place with a cut-out having been made to allow for the under floor venitlation.

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Here's a picture of the back wall of the extension showing the wall having been built up to the DPC level.

I was pretty pleased with myself at this stage, but I was about to discover four mistakes that would need resolving.

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Having gone around the wall and worked out where the doors were going to go I realised that there was one of the air brick vents in the location for the french doors in the kitchen.

As the doors will (obviously) be at floor level, which in this case is the DPC level, the air brick cannot also be above the DPC.

I had to cut out the bricks below the air brick and lower it one course. This means the bond doesn't match, but this is going to be under the sill of the doors, so not exactly noticeable.

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Around the corner there is a door into the garage and also one into the utility room. I realised I had completely forgotten to leave a gap for them, so had to knock that corner down and do it again.

In fact I had to re build it twice, because the second attempt had the utility room door in the wrong place. It was only half a brick out, but that would mean three kitchen cabinets wouldn't fit on the wall in there... so it was a third go at that particular corner of brickwork and, hopefully, I've got it right this time.

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Back to the french doors again and it occured to me that as there was not going to be a wall there (obviously, it is a door after all) there would be no brickwork above the joist hangers to retain them in place properly.

A search on the internet revealed that one method is to have a trimmer to hang the joist on under the opening, but that would mean double joists either side and ordering some different hangers.

After a think, I realised that there was enough foundation at the side of the wall that I could build up from that to provide support for the joists under the door opening, that seemed much simpler.

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My fourth mistake, wasn't really a mistake to be honest, more an unfortunate circumstance.

When considering the joist hangers that will need to be placed in the existing house wall I will need to cut slots in the brickwork. The original intention, and the ideal situation, would be for that slot to be at a level of the mortar and not a brick.

Alas this was not the case and as can be seen in this picture quite a bit of brick would need to be cut out. There is also an issue that the hangers are 200mm wide, so at 400mm spacing I'll need to remove half the wall!

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The previous picture also shows the solution to the joist hanger problem.

What I did was to sit the DPC on a thick mortar bed which brings the level up so that it aligns with the mortar course on the existing house, this means I can cut a narrower slot in the wall.

I've also re-adjusted the joists to 600mm spacing (they are well over the minimum size for this anyway) and that means removing less of the wall.

In this picture you can see the DPC carried all the way round the wall like this and the joist hangers are now at the desired level. The bricks along the top are just to hold the DPC down, its supposed to stick, but it doesn't always.

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Raising the DPC on the inner leaf also had one other advantage.

Up until doing that the outer brickwork was fractionally higher than the inner, that's a no-no with the wall ties sloping back towards the inside as there is a chance moisture wll transfer along them apparently. Now they slope the right way, to the outside.

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The final two courses to bring the brickwork up to DPC around the garage have been added along the side.

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At the front of the garage I've returned the two side walls. I measured out the centre and then back to the wall to get the gap, something went a little awry somewhere as it turns out the walls at the sides have a 20mm difference in length, this means the door is 20mm off-centre, I can live with that though.

I decided to fit the door flush with the front so had to make the opeing wider than I first expected to. I'll deal with the exposed bit of the cavity when I put the door in. The thought at the moment is to put a threshold strip down which will cover the gaps and give a neat appearance. Some plain u-PVC soffit board across the front should do that.

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It turns out I hadn't finished with the back of the garage. After discussing it with the bricklayer he recommended adding a DPC layer at the level of the bottom of the doors and then another two courses above the paving level.

So, it got knocked off again and rebuilt for the fourth time..... I am confident it is correct now.

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The remainder of the foundation under the toilet turned out to be in the way of getting one of the joist hangers in place. I could have placed one either side (just), but that would have made the positioning of the remaining ones difficult, so it needed to be cut back.

It was a pretty tough bit of concrete but a large SDS drill, a pointed bit, and a bit of perseverance chipped it back to allow clearance for the hanger.

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Whilst in that area it was time to sort out the missing section of wall under the floor in the toilet area. This is the area where the underpin was added and now the wall needed to be brought up to a level where the joist hangers could be placed.

I started out by clearing back the remainder of the earth under the floor to create clearance and then using a straight piece of wood placed across the face of the walls on either side I was able to take a level down and measure back to place the first course.

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The cavity on the existing wall on the right is 70mm, whilst the new section on the left is 100mm. I've built this section with a 70mm cavity as the difference can be resolved more neatly at the corner on the left.

Here I've placed the first two courses on the inner leaf of the wall. I back-filled the gap as I went. There will be no loading on this bit of fill so it is only really to prevent there being a void.

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This is the completed inner leaf of the wall. It is a little short of the perfect height, but that'll be sorted out when the floor section is removed and the wall above is demolished and re-built as desired without the existing doorway.

I've wedged a few half bricks in the top to support the edge of the floor slab and give it a little more strength.

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I built up the outer leaf 70mm forward of the inner one to align it with the face of the existing wall and stopped one block course short of the top.

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The bottom of the cavity was then filled with concrete.

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Having strung a line across to get the level I completed the wall.

This is now ready for some mortar and the DPC before adding the joist hangers. Once we've finished using that door the wall above will be built up.

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Whilst working on some other items I returned to the area where the french doors will be.

As it was decided to make this opening wider the wall to support the floor also needed to be extended.

Having some mortar mixed up for various jobs I laid a few more blocks in to get the correct floor support wall width.