An extension build

[Karl]

Hello.

I'm having an extension to the back of my house built which has taken about 2yrs to get underway, and thought it might be fun to document it somewhere. I considered cutting a youtube video together, and then wondered whether I would actually follow through with that, and this is meeting my own brain halfway.

This is the back of the house. The crappy dirt area used to be a load of rotten decking that I've taken away, along with around 36 rubble sacks of smashed up patio.

On the left of the photo is the kitchen, and the right of the photo is the dining room.

The plan is to knock down that lean-to which forms the end part of my kitchen, making the two sides level again, and to extend out 2.5m from the house, and across the width (which is around 6.5m).
From there, we'll then knock down the internal (load-bearing) wall separating the kitchen and dining room, creating a larger open space, and using some of the wall that's left to form a partition for a small utility room for washing machine / tumble dryer.
We will then move the kitchen from the left side of the house to the right, and use the length of that wall to put cabinets.

The existing house plan looks like this:

We will be altering the layout to be like this:

We'll have four large bits of steel going in to the house to replace the load bearing wall, and we've had a structural engineer do all the calculations to ensure that everything is supported as it should be.

We also have a chimney breast on the exterior wall of the dining room and first floor bedroom which will need to be removed so that the kitchen can sit flush against the wall.

If people are interested in the process of me getting to where I am at the moment (build beginning), then I'm happy to answer.

 

[Karl]

First week - Demolition of lean-to, digging foundations, pouring concrete

Lean-to coming down.

Lean-to is down, and the external wall is being kept in order to give us some solid foundation to build upon for the steels / extension block work. A partition has been put up so that we can continue to use the kitchen for the time being, until the steels go in and the external wall has to go!

Digging out foundations. Really quite deep!

Concrete arrives

Concrete goes in.

Concrete is in, it has the weekend to set, blockwork starts on Monday.

Taken from the first floor third bedroom - We realised that the guttering for the old lean-to goes literally nowhere, so needed to dig a soakaway.

 

[Karl]

Like your layout, loads of space there! We use our driveway which runs along where you've widened your kitchen, so decided not to head out that way.

When was yours built?

1930s at some point I think. The foundations are paper thin

Whats your budget? I imagine prices have increased a bit in last 2 years!

I think we're going to end up touching £75k all in.

Are you having the extension rendered?

Yeah I'm leaning towards having the entire extension rendered rather than carrying on the brick fascia, because the renders won't match anyway, and the original render is starting to fail and will need redoing at some point in the future anyway. May as well make a bit of a feature of it

Are you doing anything to the existing?

The kitchen is swapping sides, so that's going to be a huge undertaking, and we're having two floors of chimney breasts removed to make the wall flush which is going to be highly disruptive, especially as the bedroom upstairs is my two sons' bedroom (3 and 6)!

I think we're going to end up moving in with my in-laws for a couple of weeks at least when the kitchen moves. We're holding on to it as long as possible because I don't want to go there too soon and the full force of my boys cause us to outstay our welcome

We did a very similar thing back in 2015-16. The separate utility is worth its weight in gold!

Looks like a lovely project. Glad things are moving forwards. Good luck!

Thanks mate. I'm really looking forward to having some living space separate for the boys, and somewhere to continue to shut the door on the noisier appliances. Two kids means CONSTANT washing.

 

[Karl]

Second week - Felt a lot slower this week, the first two courses of bricks have been laid to show the shape and dimensions of the extension, and the concrete pads that the steelwork will be based upon has been laid.

There's been a fair bit of clear-up as well, so it's all good progress, but less to show for it than the first week.

First bit of block work going in

Started to insert some props to hold up the house once the lintels are removed and the steel framework is put in to place

Some big holes dug either side of the house for the new concrete pads

Bit of levelling out

Concrete in place

Another skip's been filled (that's 4 so far), probably another one next week, and the site's looking a lot tidier now.

Next week there will be more props going in, some brickwork and old lintel removal, and hopefully in the middle of the week, a half-tonne piece of steel will be going across the top opening of the house

 

[Karl]

Something I always wondered is how you get a full width steel in place in existing brickwork. I can see you've starting supporting with props, but at some point you have to have a full width of brickwork removed to get the steel in and the brickwork above it sitting on the steel. How is this achieved?

I’ll document this so you can see

 

[Karl]

Subscribed! How did you select a builder? Seems a minefield when we’ve looked into it.

We asked for quotes for a smaller job, removal of a chimney stack. We got a guy in, he turned up when he said he would, did a good job, and billed us what he said he would. We went off that, plus word of mouth recommendations from neighbours who had used him for their works. Word of mouth is better than Trust a Trader and all that IMO.

Ooooooo, I love a project build. Looking forward to all the cool updates.

On the garden front, are you planning on removing those ugly and chunky bushes against the neighbours fence?

Removing those and getting some slimmer plants in there (E.g. prunus amanogawa, lower level grasses etc) will really help make the garden an awful lot bigger with more usable space.

The bushes are going to go, yep. Thank you for the recommendations on plants; we were looking for ideas on what to put there that wasn't going to go utterly mental, like the stuff the previous occupants put in. We were also thinking of taking the tree-type thing out that's opposite those bushes up against the garage, and replacing them with something like a climbing rose, or something else that'll go up, but not out!

 

[Karl]

When I work out how much it costs I'll let you know

Probably ~£70,000 but we'll see.

There's a sofa (maybe a chavvy corner one, watch out GD!) plus TV going in to the new area where the kitchen used to be, which will be a lounge area, so we'll have that, plus planning to have a small patio outside the bi-folds where we'll have a small bistro table for morning coffee and so on. We'll keep the lounge where it is, because when the kids get older, we want somewhere to retreat to if they have their friends over for console gaming / white lightning.

 

[Karl]

Bit random to jump in here, but when you say removal of the chimney stack, was this full height, or just partial, and was the chimney load bearing in any way?

No problem. It was a full stack which was taken down beneath roofline. There are two chimney breasts beneath it, which we will have taken out as part of this extension work, but they are currently still in place.

 

[Karl]

Are they load bearing in any way or is it just a side of the house stack? Ours is central and load bearing, but i really want to remove it, at a minimum down to 1st floor level to gain more room in bedrooms, doing this also means we arent removing any load bearing structure.

it only supports itself - the chimney breast at ground floor supports the first floor one, supports the loft structure beneath the stack, which supported the stack. It's on an external wall of the house which is detached, so no additional load requirements there. Not sure on your situation, but it likely won't be as straight-forward as my situation was here if it has additional load-bearing requirements.

 

[Karl]

We did something similar in 2018 at our old house and it cost ~£40k including the new kitchen and flooring. Have building costs really gone up that much?!

PS. Isn't that first course on foundations supposed to be engineering bricks?

Yep. Building costs have risen significantly since then - This was actually one of the cheapest quotes we were offered, and costs have gone up since the quote was prepared, but the builder is honouring the original labour quote from last year.

As for the bricks question, you can use engineering bricks or higher density breeze blocks which are DPC certified (which these are) - each brick weighs about 25kg

 

[Karl]

Bumper photo post today.

Here you can see that the props have been put in to place a specified distance apart to hold up that side of the house. A few more props were put on the left side, though a lot of it was held up by that enormous concrete lintel. Once this was done, the builders started chipping away at the brickwork underneath these props, until the props signified the base of the house's load-bearing structure.

From here, the house was ready for the steels to go in.

Me for scale, and just because

The lifts arrived the day before.

Steels delivered. The longest one to form the crossbar of the goalpost shape is 250x250mm in width / depth, and is 500kg.

Four of us + these cool massive skateboard thing managed to get the biggest one down my driveway and very slowly, but surely, moved on to the two lifts.

Had to swap out a few props to slowly shift the steel in to place.

The winches on the lifts were then cranked at the same time (with a spirit level on the middle of the steel) to slowly lift it up to its position.

From here, the two uprights were put in to position each side (much lighter!) and bolted in to position, whilst the lift held the central steel. Ground anchors went in to place on the uprights, and blocks, slate and adhesive were used to fix the steel in to place with the brickwork, to ensure the house's brickwork had no room to move in the future.

From here, next week will be building up the shell of the extension, hence all the blocks being delivered. Hopefully by the end of next week I'll have something cool to post.

 

[Karl]

Out of curiosity how big is your opening (Oooh matron) and costs of steels?

Sorry if I missed it.

Opening of what? The width of the extension will be 6.5m or so, but the bi-fold opening will be 3.5m

 

[Karl]

Good progress.

I'm no structural engineer but I can't help but look at that main horizontal cross beam and think it should be on top of the two vertical steels, rather than just bolted to them. A lot of weight (including the beam itself) relying on the shear strength of those bolts.

It must be fine though or building control wouldn't have signed it off.

Structural report excerpt:

Building inspector visit on Monday / Tuesday next week, so I'll let you know if anything shocking is decided

 

[Karl]

Like I said I'm not a structural engineer . I'd think there would be some clamping forces to take in to consideration but I'm not a mathematician either!

Perfectly valid comment!

I'm only a few weeks in, and so far I've had:

- Wrong bricks
- RSJs don't look sturdy

I reckon next week I might get "wrong colour mortar" or "your insulation doesn't look like it tastes very nice"

 

[Karl]

The bolts will be fine, they will be over specced to have multiple methods of failure I.e. 6 bolts but only require 3.
It does look like you're missing a bolt on the right hand side.


Did you not consider putting the steel "up" into the joists so you don't have the steel bulkhead in sight? It's a bit more effort and would break into your rooms above, but visually a lot more appealing. (i shouldn't mention it, not much you can easily do now!)

Did consider it during drawings, but it's up there now...

 

[Karl]

Week 4:

The whole building collapsed because the bolts failed.

Only joking.

Floor joists have gone in, and the perimeter of block work began.

Wife for scale.

The steel lintel going above the bi-folds was meant to go in today, but unfortunately it hasn't been manufactured in time, so that'll be done next week now, along with the gables and roof construction.

Oh, also, the building inspector came and signed this stage off, so will next attend when we've go the roof on!

 

[Karl]

I chose the bolts myself.



(We got pros in )

 

[Karl]

No you’re right they are smaller. The updated drawings have a lot more detail and text all over them, so probably easier to look at the ones I’ve posted as an idea of what we are trying to achieve. The model is largely the same but you’re right the opening is a bit smaller.
For what it’s worth, the opening is 3.6m for a 3.5m door that i mentioned earlier in this thread.

 

[Karl]

Far too soon for the bi-folds tbh. They'd get damaged - later the better. Just before they plaster.

The lintel is the load bearing steel to support the gap for the bi-folds. The doors themselves won't go in for at least 3 - 4 weeks.

 

[Karl]

To be fair, getting a steel to support a span of 5 odd metres I believe you start getting increased depths, which you don't want, so it's a bit of a balance.

Any more photos?

Trying to keep them weekly so that I can summarise a little bit, but here's one of the lintel in, plus a bit of roof:

Any particular areas of interest?