saveasteading

First do as @prodave suggests. That is probably only for your comfort, and won't change much. I often lecture people about not adding too much water to the mix. Very wet concrete shrinks quite a lot and is weaker. In your case this doesn't really matter, but its still for the best. And we do want the mix to permeate in to the depths of that hole. Being pedantic I might suggest adding a plasticiser to the mix. This is a liquid that bricklayers use. it produces bubbles which make the mix more fluid, and also have some detergent for the same purpose. How much to add I don't know though... your circumstances wont be on the bottle but will still be a guide. btw sharp sand is excellent stuff and stronger than building sand, but does not flow well. Building sand is better for that. So you would first use a mix without stones I think, so that it flows into corners and gravity will do most of the work. you should agitate it with a stick though as this will encourage it to flow and it removes any air voids.. once that has stopped disappearing and is visible, then make a stronger mix with sand, cement and aggregate. and fill the rest. I can never remember mortar or concrete mix amounts but it will be on the cement bag. Never pour concrete or use mortar unless the temperature is at least 3 degrees and rising, otherwise it fails dramatically.

I came across this at the bottom of a tool bag. I vaguely remember buying it for 20p or so in maplins clearance. For stripping and cutting cable? Any special use or advantage over a conventional wire stripper?

Polythene on the outside of the stud would be normal. Then another inside. The bubbles will barely help so use polythene sheet from a builders merchant. Better to use polystyrene backed plasterboard than bubblewrap. Be aware that you may still have dampness through the floor.

No, there should be that distance , or close to, underground to where the the ground is stronger and away from the weather. Yours seems to be 100mm or so of concrete at ground level. So it is built more like a garden shed. There isn't much you can do. So dig that hole bigger so that you can prove it is very local, and get your arm into it to see how far it extends.

Good work. It would appear that there are no foundations, only that slab that we see. I would want to dig the hole a it wider and deeper to establish this, or otherwise. That will also allow you to pack concrete in better, as that is probably a good plan. If it is just a slab with no thickening, , then it is a bodge job that didn't trouble the building inspector or a decent builder. So you won't be doing any harm. I don't see any sign of a damp proof membrane. Is it damp inside? We can discuss the concreting later. ps @Alan Ambrose was writing concurrently.

At least carry on investigating yourself. Decision later.

That never passed a grade test by machine or inspection. I was told by a timber importer that they had quality issues with Russian timber where rotten timber would be concealed in the centre of a bundle. The strength grading would be dubious too, and I think the merchant did their own grading. That would be 1990s. Maybe one of those.

I think that's what I said. I don't know what you mean. An air gap is additional insulation unless draughty.

Don't fix eps as an exposed soffit. It is highly flammable and melts as is it burns, spreading gobbets of fire. Pir is not as awful but still not good. Incredibly these were once standard ceilings. But you could apply it then cover with plasterboard or cement board. Preferable would be to remove the ceiling and fill between joists with rockwool.

Carelessly used expanding foam has cost me £thousands. It once expanded out of a metal clad wall and stuck to the outsides. Replacement required. It was Mr Nobody as usual. I would worry about it doing the same to windows. Can it be controlled? Also it is used excessively as a bodge to hide poor work, and that can't be removed to do it properly.

Help us to help yourself. Clearing the area. What is there now? How accessible is it.? Clear site and prepare. 2 days? Dig trenches. 1 day? Pour concrete 1 day Block or brick walls 2 days. Stone base 1 day Concrete slab 1 day Clear up and leave. 1 day 1 day float Does that sound right? 10 days x 2 men at £250 = £5k. Materials about £4k Add 20% for overheads About £11k Add 20% vat. 13k More if tricky access, biggish firm , anything you havent mentioned, drains, insulation if required, London or SE.

Yes @iSelfBuild. We are here to advise but not design. The advice now is that it can be done and that you need professional advice and more money than you first hoped.

@LnP thanks for that link. I was not aware of this document so will read it thoroughly later. It's a great example of what I was going to say which is basically...it is complicated and ultra important. i have designed and built buildings for decades. Hundreds. I thought I was expert on fire risk. One of our steel buildings was exposed to extreme fire and the fire chief said he'd never seen such good resistance. And yet, when I went on a 3 day intensive course I learnt much more. Professors study nothing else, and what we see in the regulations is a summary. Building inspectors rightly want to see proven constructions as any variation creates a risk. That can be frustrating when you have a special circumstance of a 'great idea' but safety must come first. Why should they accept a variation. Even so, we find that kingspan and celotex ( do i say allegedly still?) cheated their fire tests. @ARC GuitarsWhat are you paying the bco? Typically about £1000 for the whole project. That is what 4 days of a tradesperson will cost, or 1 day max of a professional designer. The bco is not your designer. On the positive side. A timber housing estate here won't burn like in Los Angeles. Timber needs air flow if it is to blaze and spread. Working to the regulations prevents that.

Altnaharra, not too far from you was coldest last night. On other occasions the warmest place in UK.

Unfortunately not. I think you will have to take the foundation down to next door's ground level.

The sketch is perfect. Thd issue is the load of the new building thrusting against the existing retaining wall. Imagine loads spreading at 45 degrees. What is the wall construction? Keeping the gym dry inside will need careful detailing and some cost. Will there be a door at ground level and steps down inside?

No. You know better than that. Controlled ventilation requires an absence of draughts. Airtight first, ventilation second. Unless the occupants are wearing warm clothing.

I suggest first establish what geometry is best. There is no point in having an unpleasant space. Then we look at the best way to build it. Lots of insulation for sure, and draught free.

Good idea. Who starts it? It needs either a leader who has the final say on the submission, or a defined group of editors.

Terraced Victorian houses were generally built with regular rooms and one chimney stack serving 2 houses. It is unlikely to be a convoluted stack with different room arrangements. Could well be OK, is a big assumption.

Does this small shed not lend itself to 'stick build'? Any decent builder or diy'er could do it and it would be customised and probably sturdier.

To me yes. I think anybody who might be doubtful won't notice unless i point it out, so i won't. Iive learnt a bit about the foibles of these so the next use, on a more important wall, will be improved.

I have been repurposing concrete shutters as timber wall cassettes. We had to do some unexpected work, in removing a perimeter slab edging of insecure blockwork, and pouring a new ring beam in its place. A few £k in the wrong direction. To mitigate this, we made the shutters higher than necessary (could just about have been 400mm, but made them 600). Thus they are mostly half sheets of ply, 2400 x 600, with 4 x 2 framing. The builder understood this and removed the shutters with minimum damage. I have been erecting them as a kit-form enclosure in the garage. I will summarise my own pluses and minuses later. I have pictures and will attach them to a later post direct from the phone, for my own ease. It's obviously better for the world than burning them, and dismantling isn't easy as the screws are well embedded in the ply. They are dirty with mud and concrete too, but most of it will be over-clad in timber or metal. But they are making a rather low quality of wall, so I have dropped my own score from 100% to 80%. Perhaps a proper joiner would do better, but equally wouldn't like working with compromised material.

Sorry to worry you. But a daughter had a house where the chimney had been removed completely in the rooms but remained in the loft and above. It was not supported in any way other then some bits of wood stuck in gaps in the loft. It had hung on there for many years by the look of it. I had not spotted this before purchase and neither had the surveyor. It hung on simply through the ability of brickwork to cantilever. If the house next door, sharing the chimney stack, did the same then i would likely be disastrous. we built in gallows brackets an all was well. So first look more at where chimneys come out of the roof, and neighboring properties if they are the same model, and talk to the neighbours alongside and below. If you think there has been a chimney removed then don't despair. 1. you haven't committed yet. 2 It may have been removed properly. Doing it properly involves building inspector approval and inspection. Perhaps they can advise. Doing it retrospectively will make a right mess of downstairs, but it is they, or their predecessors who have caused it. Nobody wants the building collapsing, so do not be shy in asking around. If there is a surveyor involved yet, make sure they know your concern. Ask the agent too...they will duck it but it will be on the record. Well done for spotting it. Lets hope it isn't a problem.