Building a Domestic Extension in Stages

[CHarr]

I've had no luck in obtaining quotations from builders for a single-storey side and rear extension to an average-sized 1950s semi, so I'm trying to get quotes from separate trades to do the job in stages, instead:

Stage 1: Demolish an existing garage and clear site.
Stage 2: Excavate and construct foundations & alter drains/services.
Stage 3: Construct walls in brick & block.
Stage 4: Construct and tile roof.
Stage 5: Doors/windows, electrics/plumbing, plastering.

I've got Stage 1 sorted out, but I'm not sure where Stage 2 becomes Stage 3: should the brickwork below DPC be 2 or 3?

I don't need to worry too much about Stage 4 yet, but how far should Stage 3 go, for a roofer to be ready to start Stage 4?

 

[PrenticeBoyofDerry]

You cannot but a roof on, without the walls being built, so that question really answers it's self.

 

[CHarr]

You cannot but a roof on, without the walls being built, so that question really answers it's self.

Thanks: I'd never have worked that out all by myself.

The issue for me in defining these stages (not the sequence of them!) is whether the wallplate is really part of the roofworks or of the wall construction.

 

[CHarr]

So far, so good. Lots of decent quotes for the demolition stage received, and our preferred tradesman can start tomorrow. He's interested in the foundations & drain laying job too, and at last, our relatively simple extension will be under way.

So I need to put Building Control on notice that we're starting, and get that cheque book out. Looking for a bricklayer, now.

 

[limerockconstruction]

Although we project manage a lot of our own builds we still occasionally put up the odd shell for developers and surveyors we have done work for in the past. As bricklayers by trade, I would always price to bed the wall plate on and strap it down - with it nice and level the Chippys have got an easier job.

 

[CHarr]

I've got Stage 1 sorted out, but I'm not sure where Stage 2 becomes Stage 3: should the brickwork below DPC be 2 or 3

A semi-retired bricklayer doing a very small job for me today suggested that he'd far rather work directly off the concrete, than build off someone else's DPC - fair enough.

 

[limerockconstruction]

I'm in agreement with your retired mate, if i'm subbing I would always stick my neck out to do the damp-course blockwork as well, that way we know the building is set out correctly. If I don't know the ground-worker i'd also do a walk around the foundations with the laser level before laying anything just to point out any inaccuracies as it may be difficult to lay off of a ****e foundation.

 

[taz123]

I've got Stage 1 sorted out, but I'm not sure where Stage 2 becomes Stage 3: should the brickwork below DPC be 2 or 3

A semi-retired bricklayer doing a very small job for me today suggested that he'd far rather work directly off the concrete, than build off someone else's DPC - fair enough.

That's understandable, the setting out/ bonding/gauging is the most important part imho.

 

[noseall]

If you are having roof trusses, then a monkey could bed the wall plate and struggle to get it wrong.

If you are having a cut roof then the plates need to be level, square (if hipped) and parallel.

There are many things to consider throughout the various stages of building an extension, right from the outset. Simple things like the finished height of the foundation concrete and drainage can come back to bite you later on, if you end up with selfish, money orientated trades people.

You will need to be diligent and get wise to building straight away.

 

[CHarr]

Things are going OK, so far. The existing garage has been demolished and site cleared ready for foundations excavation, and building control have been along for a first inspection.

We've got 19 linear meters of trench at 1m x 600mm to excavate, which will be mass filled with c9 cu mtrs of concrete to 225mm below DPC, ready for brick/blockwork up to DPC. Some drain laying and preparation of the internal area for floor sub-base, and that will be Stage 2 underway.

Anyone care to guestimate the likely total cost? I know the concrete will cost £900 + VAT (for mixing and pumping on site).

 

[noseall]

225mm below dpc is too close for the finished foundation concrete level.

You need double this at least.

 

[CHarr]

225mm below dpc is too close for the finished foundation concrete level.

You need double this at least.

Why? It's what the designer has specified.

 

[noseall]

Why? It's what the designer has specified.

Your designer is a cheddar horn.

225mm will allow no tolerance for paving falls or bottle gullies and could have other detrimental consequences.

It's your call but it is risky.

 

[limerockconstruction]

Why? It's what the designer has specified.

Your designer is a cheddar horn.

225mm will allow no tolerance for paving falls or bottle gullies and could have other detrimental consequences.

It's your call but it is risky.

I don't know what a cheddar horn is, but nonetheless I'm inclined to agree. Should aim for 450 min

 

[CHarr]

Should aim for 450 min

So six courses of brick, not three? I can see the point about gullies, and wonder how the reduced cost of concrete (I'm quoted £78/cu mtr) compares with the additional labour and material of the brickwork.

Does anyone have a guestimate of the cost of constructing such a foundation (excluding the brickworks - just up to concrete level). Thanks