Mike's ext'n & renovation (solar panels)

[Mike G]

Why do digger teeth marks need removing?

There is supposed to be a nice flat bottom on the base.

 

[TheTiddles]

Deleted

 

[Mike G]

I really don't know.

I guess if you were in pure clay, nothing fell in from above, and the teeth marks were clean (ie not crumbly), then the Building Inspectors probably wouldn't be bothered. The fact is, stuff falls into the trenches from the top, and that needs to be dug out. If you've got depressions an inch or more deep, the loose stuff will settle in there, and the bottom therefore won't be clean, even if you scrape with a shovel. That's my guess as to the primary reason for removing them.

My first job with a shovel around the newly dug foundations was to pull back all the loose stuff from the edges; anything that might fall in, or get washed in if it rained. Luckily, the ground is brilliant, and most of the outside is grass, binding the topsoil together, so we had very little drop in. I've worked on other foundations where you return the following morning to find tons, literally, of material having collapsed into the trench, with sides collapsing, or loose top edges falling in. With this one, I can be pretty confident that my volume measurement for the concrete is going to be accurate, and without even looking this morning, I know there will be no debris in the trenches.

 

[Frank]

Mike in your opening post you referred to stripping back the original building to its frame, at that point will you be under pinning the original in some way?
I only ask as I was wondering if being on clay you had concerns with heave & if differing footing could lead to problems.

My own property is on clay with no footings other than bricks laid in a triangle to a width of around 27 inch on the bottom course, I'm thinking of building an extension but am concerned that the new footings will be considerably more substantial & will resist any heave in the clay more than my present footings.

I would be interested In your opinion on this.


Kind regards,

Frank.

 

[Mike G]

Hi Frank.

Strictly I won't be underpinning, because there is no existing footing. I will be putting in a new foundation and plinth. That is just semantics........essentially I will be doing exactly the same under the existing house as I have just done under the extension.

I have a bit of an issue with the problem you describe. I understand the reasons for it, but the problem of differential movement between a modern extension and an older property with no foundation, or just a thickened out base to the wall, is quite a big one, particularly if the work is in masonry. It is far less of an issue with a timber frame building, and if your existing building is a traditional oak-framed one, then I would certainly suggest that you build a timber frame extension.

Indeed, there is a lot to be said for having a timber extension anyway, particularly if it is clad in boarding: you can always hide differential movement at the joint if there is boarding involved (externally) Internally is always another matter. Whoever designs your extension should design for differential movement. With good detailing, a bit of thought, and decent workmanship, you should be able to manage the results of the movement even if you can't eliminate it.

Mike

 

[Mike G]

Here is the water duct as mentioned yesterday:



The first job of the day was to put in level pegs for the top of concrete. This is worked out to suit brick courses, so that my brick plinth will arrive at the required level without cutting any bricks....in my case, the foundation is 975mm or 13 courses below the top of the existing plinth. The pegs were set with a laser level, but only because the digger driver got his kit out before I got my old-fashioned dumpie (Cowley level) out first. It's a simple process: measure down from the plinth to the level you want, and hammer a wooden peg into the side of the trench. Re-check. Set the staff/ receiver to that level, and then go around the trenches putting in a peg every 1.5 to 2m. Then throw some lime onto the ground above, so that you know where the pegs are (they soon get buried in concrete.



Here's the tamper:



The lorry arrives. Friends with rakes standing by to help push it all around.



Me tamping whilst the pour goes on:



A second lorry arrived to deliver at the other end of the footing. The driver was really helpful, and put his lorry where some wouldn't have dared.



I knew there was a reason I kept those old doors .



Pulling the concrete around by rake:



We had to wet the mixture up quite a lot to get it to flow into all the nooks and crannies, and to go about 12 metres in distance. Thus once the concrete is in to level and tamped, there is a film of water on the surface.



Despite having 3 additional places for concrete (an oil-tank base, and 2 small footings for lean-tos on the workshop), we still couldn't use up all of the second load.

As always, that is the end of the stage of building where costs can escalate meteorically. Because of the good ground conditions, and because we found nothing in the ground that caused any additional work, it cost only £2000 to get the foundations in, which is great.

 

[AndyP]

Fascinating as always. Next time I see foundations being dug I will check the trenches to make sure they have flat bottoms. I'd no idea that it was so critical.

 

[chataigner]

No steel reinforcement in the foundations ? I'm a complete novice, but here (SW France) reinforcement steel would be usual...

 

[Mike G]

No requirement for steel. The ground here is completely inert. All that the foundation is doing is spreading the load of the house. It doesn't have to resist any ground movement, and the ground is consistent, (ie no soft spots) so the concrete isn't having to bridge across non-loadbearing areas. There is always steel involved if there are piles.

 

[kirkpoore1]

No steel reinforcement in the foundations ? I'm a complete novice, but here (SW France) reinforcement steel would be usual...

Ways and customs different from our own, I guess. Not only would rebar be required here, but bolts or some other kind of fixture would be needed to tie into the next level. Then again, we have to be ready for freezing or tornadoes or earthquakes or hurricanes here, depending on location, and you guys don't need to worry about any of those.

Kirk

 

[Mike G]

Yep, dead right guys. So much depends on the local conditions.

In Darwin, Northern Australia, for instance, steel cables are attached to the foundations, then taken up and over the superstructure and fixed to the foundations on the other side, then tensioned. This to prevent cyclone damage.

You can tell from the fact that there are 700 year old timber buildings in this area without any foundations at all, let alone thousand year old churches built straight onto the dirt, that our conditions are relatively benign.

 

[Mike G]

I have let the concrete go off for a couple of days, so thought I might reduce the oversite. This means stripping off all the soil down to the underside of the build up for the floor slab. My floor, working from the top down, will consist of 75mm sand & cement screed (with underfloor heating pipes), polythene separation layer, 75mm Celotex insulation, 100mm concrete, 1200 gauge polythene DPM, sand blinding, c.150 crushed hardcore.....so I need to reduce the ground level to approx. 400mm below finished floor level.

Before I did this, I had to set out for the curved retaining wall, because I will be eliminating the centre point, and if I don't do it now, setting out a circle will be so much harder.



As I won't be digging that out until the spring (I don't want the site to turn into a mud-bath), I had to mark it in such a way as would survive for 5 or 6 months, so I cut a little channel and filled it with lime:



Then I got to work with the digger:





I piled up as much as I could, and ran out of room to dig. The digger driver is back next week, and he'll load this on a lorry, then clean up properly. The little digger can't handle the big flat bucket (probably 1500 wide or so, but critically, lacking teeth). This will give us a good surface to work from.

I've ordered bricks and blocks, so once the oversite is cleared, it's on with bricklaying.

 

[9fingers]

I don't think I recall hearing about the curved retaining wall before Mike.
The site looks quite level so far so I'm a bit curious about what is needing retaining?

Bob

 

[Wizard9999]

I don't think I recall hearing about the curved retaining wall before Mike.
The site looks quite level so far so I'm a bit curious about what is needing retaining?

Bob

:text-+1: Same question sprang to mind when I read this.

Terry.

 

[Rod]

Perhaps a moat? [emoji3]

Rod

 

[Mike G]

I don't think I recall hearing about the curved retaining wall before Mike.
The site looks quite level so far so I'm a bit curious about what is needing retaining?

Bob

I haven't mentioned it before, Bob, but the house floors were lowered, I guess in the 1970's under the Home Improvement Grants scheme. This put them well below ground level, and so they sloped the ground down to the house, all round. The high point of the lawn is some 700mm above the ground level at the house wall, and the man-made depression in which the house now sits is undrained. So that all needs sorting out.

Here's a sketch of the proposed landscaping. Consider it an opening of negotiations......

 

[firedfromthecircus]

So who owns the land to the right outside the current boundary?

Looks like a nice set-up.

 

[Wizard9999]

So is the plan to buy more land outside the current "registered boundary"?

Terry.

 

[Mike G]

Yes, before we even bought the place the farmer offered to sell us as much land as we want.

 

[TheTiddles]

Deleted

 

[Mike G]

Curved retaining wall like a dam, nice idea, though I guess it's more for aesthetics?

Aidan

100% for aesthetics, Aidan.

 

[Wizard9999]

Yes, before we even bought the place the farmer offered to sell us as much land as we want.

Lucky you! :mrgreen:

 

[RogerS]

Mike, presumably your extension will have all the well-insulated bits and pieces that are your 'signature' as it were. But will you be retro-fitting stuff to the existing building? If so, I shall watch with even more interest !

 

[Mike G]

Hi Roger.

Yes, the new-build will be my usual inside-out timber frame, super-insulated, triple glazed and a ventilation system serving the whole property. The old part will be stripped back to the frame, then Celotex between the studs, and 100mm of sheeps wool insulation outside the frame, across the face of the studs. I'll then batten out and lime render. This means the existing house gets c.5" of build up on every wall, so will be 10" wider and 10" longer. The plinth will be rebuilt to suit the new lines (the plinth, like the rest of the house, has been wrecked by having a rock hard sand/ cement render applied over the old soft-red bricks).

I think the re-built walls of the old house will have a U value of about 0.13, and still be breathable. The ventilation system will make sure that there is never again a build up of condensation internally, or interstitially. I obviously won't be showing any timbers externally, but the principle timbers will be on show internally. The increased roof overhang will be catered for with sprockets.

From the above, you'll see that the finished property will be a combination of lightweight (the existing), and thermally massive (the new). It will be interesting to see how this performs, but I'm not expecting to have big heating bills, with my normal target of £100 per year in mind.

 

[RogerS]

Really looking forward to seeing that pan out, Mike.

 

[Mike G]

So do I Roger. I'm already getting people asking me when it will be finished!!

 

[StevieB]

At the rate you are going Mike I would have thought by Christmas was a distinct possibility!

 

[Mike G]

Don't you start, Steve!

If I have finished the extension and the renovation by christmas 2015 I'll be pleased, I think. The renovation could take some time. One fly in the ointment is that I will probably have to have a carpal tunnel operation (or two) done in the next few months, and that means weeks off.

 

[9fingers]

Are you living in the place during the work Mike?

We did this when adding both an extension and an extra floor on our bungalow. We have "lived" in nearly every room in the house as a bedsit during the course of the works.
Having to keep the property functional, dry and secure at all times was a bit of a pain and sometimes meant the work had to proceed in a less than optimum order had the place been empty.

Bob

 

[Mike G]

Yes, we're living in the cottage. We'll move into the extension when that is finished, and start work on the renovation. When I say "living"...........it's a bit more like camping. Almost all our possessions are in a shipping container on site.

 

[Mike G]

The plinth materials turned up today:

 

[Mike G]

Here is the site stripped to levels and cleared:





Just to show the slope of the land I referred to previously:



I am pointing the piece of batten at the underside of the footing of the existing cottage, which is about 2 inches below the current (reduced) floor level:



It's November tomorrow!!!!!!!



Right, the serious stuff. I spent hours re-setting out, using a datum along the back of the house. Some of my previous setting out turned out to be very accurate, which must have been an accumulation of errors, because I was working from the curved line of a portion of the rear wall. Now I can get to the whole thing, I can be much more precise. I needed the datum line, and a line at right angles to it. I did this with a 9m, 12m, 15m triangle, which should be extremely accurate........but I won't really know until the brickwork is up.

For those who haven't seen brickwork being started, you string your line between marks (nails) on the profiles, knock up a strong mix of mortar (mine was stronger than 1:2 cement to sand), and spread it as thinly as possibly at the corner locations. You then need to drop the line of the string down onto the wet mortar, which you do with a spirit level.....and patience, particularly on a breezy day. The other notable thing in this photo is the vertical batten driven into the ground near the corner. There is one of these at every corner, and they have been set to the height of the plinth using a laser level. They are accurate to within 1mm, which means I have no excuse if the brickwork isn't horizontal:



I do this in a couple of places per corner......once at the corner, and then again about 6 feet away, then lay a straight edge between the two and mark with the edge of the trowel:



Your first few bricks you just have to be careful not to spread too much mortar around, because it will obscure your marking out. Mine isn't entirely set out yet, because I ran out of light whilst I was scratching my head over a difficult corner. Difficult because I haven't got a location I can put a second profile, unless I do a temporary one within the excavation. I'll work something out in the middle of the night.....when all my best thinking gets done.

 

[Mike G]

I know how much you all like a little quiz question, so here's a couple for you. Here is a drawing of the section through the plinth of the extension:



1/ Which brick will I lay first.......A, B, or C?
2/ Why is there a course of bricks under the block courses?

 

[TrimTheKing]

I know how much you all like a little quiz question, so here's a couple for you. Here is a drawing of the section through the plinth of the extension:



1/ Which brick will I lay first.......A, B, or C?
2/ Why is there a course of bricks under the block courses?

1/ A
2/ Because the bricks will be stronger at ground level than blocks?…or…Because you want a certain height of plinth and want to bring them up to height and that height is 1/3 of the depth of a block?

Cheers
Mark

 

[Halo Jones]

I like a quiz, but I am never very good at them!

From your marking out lines I would guess that brick B would be the first?

Are the brick courses made from some sort of engineering brick to withstand loads, or are they more frost/moisture resistant?


btw. I am really enjoying the build - and learning loads.

H.

 

[Mike G]

I'll leave it for a few others to post first before I give any answers, but I can say that the bricks aren't engineering bricks. In fact, they're the cheapest bricks I could find.

 

[AndyP]

I know how much you all like a little quiz question, so here's a couple for you. Here is a drawing of the section through the plinth of the extension:



1/ Which brick will I lay first.......A, B, or C?

2/ Why is there a course of bricks under the block courses?

1/ A or B

2) To spread the load of the blocks

What's holding up the insulation between B&C?

 

[Mike G]

The insulation is held in place by the wall ties, which are every 2nd course of blocks (ie 450mm apart vertically, plus 900 horizontally)

 

[StevieB]

B first

The bricks are easier to level than the blocks, so a first row of bricks takes out any discrepancy in the foundation pour?

Steve

 

[9fingers]

From the point of view of getting levels established then laying B first and building up to the timber, but then you will have to move bricks block and muck to the inside to carry on risking knocking the edges of the openings.
So I'd plan to always be working from the outside and lay the inner skin first C and shortly followed by B leaving A much later as it looks to be purely decorative.

As B is only a few courses I presume you will be then pushing ahead with C to get some sort of roof on ASAP to protect from the worst of the weather.

That said, I expect you have a well thought out strategy that could run in opposition to convention - exactly why we like your topics here!

Bob