Basement Shed

Hi All,

I'm hoping in the not too distant future to be able to commence work on extending my house, which hopefully includes the construction of a workshop/shed. After having lived in the house for a couple of years now, we're hoping to leave as much of the great outdoors untouched, so to get additional floor space out of any extension, we'd like to go up and/or down as well. To keep the upstairs and ground floor portions free for other uses, I'm (call me crazy) considering the development of a basement workshop.

Aside from the obvious engineering and construction difficulties (not to mention costs associated with), I'm after some feedback (preferably from those that have one) as to what works/doesn't work.

I get that the following need to be thought out:

- Access in/out for big stuff like machines and completed projects
- Air flow for DE and breathing
- Size? (I can fit at least 7 x 7m in the proposed extension footprint, possibly larger depending on how I tank the basement). I have a drill press, metal lathe, combo table saw/planer/thicknesser and band saw and would love to add a wood lathe and a milling machine if possible, maybe someone can give an indication of what sort of space they have for each kind of machine.
- Roof height (floor depth)?

Note that my block is absolutely dead flat and my house is right on ground level, so there will be no windows to the subfloor unless light wells are built.

How high is your water table? If it is high then you'll need to take steps to ensure the basement is dry.

When you go for permits don't have the drawings or applications refer to it as a workshop. Call it a hobby and crafts room. ;)

With the machines you want to put down there you might want to think of a hoist or crane of some kind above an outside stairwell.

Pete

My workshop and garage are under the house. Due to the low ceiling anything longer than 1.8m needs to be stored horizontally.
Lack of daylight need not be a concern. Lots of workshops have artificial lighting, also if you do anything after sunset it will be with artificial light.

I guess you're on the river flats and aren't expecting to strike any rock. How are you planning on digging it out? Before you can do anything you need to support the outside walls and floor all the way to the basement floor level and possibly beyond. Wouldn't it be cheaper to buy another house more suitable for your requirements? The only way to reduce the horrendous cost of the project would be to do all the work yourself, it'll take forever. Not much point in me saying any more, I think you'll get my drift.

You almost need a shaft to lower equipment in. If you put it under a driveway a crane truck can back right up. Cover it when not in use. Waterproofing and drainage will be a big issue.

Retaining wall are easy but quite expensive.

This is just an observation as i think this is common to have a basement in houses that are built in the North American. So when the house is built the basement is part of the building. What you are doing is building after the house is built and I think this will have quite a huge expense associated with it.

When we were looking to purchase a house the closes we saw to basements were when the house was built on a hill and under the house was a basement. But these were only a few properties that we found like this.

Quote:

---

Originally Posted by themage21

I'm hoping in the not too distant future to be able to commence work on extending my house, which hopefully includes the construction of a workshop/shed. After having lived in the house for a couple of years now, we're hoping to leave as much of the great outdoors untouched, so to get additional floor space out of any extension, we'd like to go up and/or down as well. To keep the upstairs and ground floor portions free for other uses, I'm (call me crazy) considering the development of a basement workshop.

Aside from the obvious engineering and construction difficulties (not to mention costs associated with), I'm after some feedback (preferably from those that have one) as to what works/doesn't work.

Note that my block is absolutely dead flat and my house is right on ground level, so there will be no windows to the subfloor unless light wells are built.

---

a dead flat block in Emu Plains almost certainly means that you're on the flood plain. And you want to add a basement to an existing slab on ground house ? YES, you are crazy.

apart from the substantial cost to underpin the existing house slab, you will need to add a dewatering system to permanrntly lower the water table under your house so that the basement doesn't float out of the ground taking the house with it. It's likely that your dewatering system will change the water table under your neighbour's houses leading to additional grief for you.

Far better to make the down stairs portion of the extension separate from the existing house -- fire, noise and dust wise with separate electrics -- with the intent of repurposing the room when you eventually sell the house.

Sorry to take a while to get back everyone.

Yes, I'm near the river (across the road from it in fact) , but I'm above the 1 in 100 zone. My front door is above the flood planning level. I have had a mate put a test bore down for water table and at the bottom of a 5.5m bore there was about 200mm of water after a decent rain. I'm already aware of the issues/ costs associated with basements. Note that the basement, should it be built, would be under the extension only. I've already looked into going under the existing house and technically it would be extremely challenging as I'm on a waffle slab, which really does not like to be undermined. However, offset to the side is a totally different story.

Without being ungrateful to the replies thus far, if anyone out there has a (semi)subterranean workshop or knows someone who does, that's kind of the feedback I'm after.


Sent from my SM-T810 using Tapatalk

In Canada I live in a house with a basement.

In terms of workshop issues, I think you have pretty much covered it
» access for machinery and material -- including lifting / lowering items into the basement
» personnel access -- stairs or a ramp
» access to get completed projects out of the basement -- depending on what you are planning to build, this might need to be larger than that to get machines into the space
» ventilation
» lighting -- even a small amount of natural light is a worthwhile. From late October through to April it's too cold where I live to open the external doors so I'm always working under lights. It's much more pleasant to have some natural light, even when it's only 5° outside.
» Dust collection -- what you don't collect at source will likely end up in the house.
» Heating and cooling shouldn't be too much an issue at Emu Plains
» vibration isolation
» noise isolation
» Fire proof ceiling
» ceiling height -- at least high enough to turn an 8' sheet end for end. 10 ft, if you can manage it, is always nice
» power -- I suggest wiring for 3 phase, even if you currently only have single or two phase from the street.

I can't emphasis enough the importance of planning and future proofing, there'll be no second chance to get it right.


As to construction ...
If you're on a waffle slab, I suspect that you'll need to use bored pile retaining walls on all sides of the excavation.

The amount of water at the bottom of a 5.5m deep bore is not much indication of the flotation issues your basement will need to cater for.
I'm guessing that Penrith Council will have fairly stringent requirements for any basement.

Thanks Ian.

I should emphasise to everyone that when I say "near future" I mean "hopefully in the next decade". Even without going down the planning for this is taking some time, trying to get as much info out of council and friends who are specialists (I'm lucky enough to know a geotech, a structural eng and a few reliable builders) before getting the architects involved with their grand plans.

Quote:

---

Originally Posted by themage21

Thanks Ian.

I should emphasise to everyone that when I say "near future" I mean "hopefully in the next decade". Even without going down the planning for this is taking some time, trying to get as much info out of council and friends who are specialists (I'm lucky enough to know a geotech, a structural eng and a few reliable builders) before getting the architects involved with their grand plans.

---

In that case I'll be a bit more expansive

In my previous life I did a bit of work with the Hawkesbury-Nepean Flood studies. Whilst your floor may be above Council's Flood Planning Level most of Emu Plains is well below the PMF. I very much doubt that Council will approve a basement located below the flood planning level and insurance may be problematic.

Just started my own man-cave digout. It's been a long process getting it all sorted and approved. I'm fortunate enough to live on stable rock that's not too hard to dig through. There are a lot of problems to be sorted with digout basements (structural engineering and drainage being the obvious ones), and getting other people to solve these problems gets expensive. Ask your professional friends lots of questions and once you have all the information, expect to have to solve the problems yourself.

The simple answer is that you probably shouldn't do it, but the far more complicated answer is that you can if you really, really want to. :)