Trimble Workshop - Foundation planning - And we're back!

[TrimTheKing]

I've got a night to myself as my wife is at a work thing and the kids are asleep, so on with foundation planning. As ever, I have questions… Probably mainly for Mr Garnham... :?

Width - Mike suggested 450mm for a 300mm wall. That fits with my Googling (needing at least 50mm overhang from wall face to foundation edge) but is dependent on a 450mm bucket for the digger (which I'm checking on) but may well end up being 500mm. I don't think that's a problem is it? And by all accounts makes the initial bricklaying easier as there's more space to work in!?

Depth - Soil round here, below topsoil, is fairly clay I think, so Google tells me BS regs are no less than 1000mm deep, and definitely no less than 900mm. Is 1000mm where I need to be looking to be, or is it overkill?

TIA
Cheers
Mark

 

[Mike G]

You'll find a 450 bucket as easy as anything Mark. They're more common than a 500. As to depth..........assuming you are still not requiring compliance with the regs.........do 900 deep if the ground is clean, dry, and even, without any roots, and pour 450 deep to finish 450 below FGL. If you have hawthorn or willow anywhere near then let me know and I'll look up how deep you should go.

In fact, as you don't require regs, have you considered a raft with thickened edges?

 

[TrimTheKing]

You'll find a 450 bucket as easy as anything Mark. They're more common than a 500. As to depth..........assuming you are still not requiring compliance with the regs.........do 900 deep if the ground is clean, dry, and even, without any roots, and pour 450 deep to finish 450 below FGL. If you have hawthorn or willow anywhere near then let me know and I'll look up how deep you should go.

Thanks Mike

It will be right up against the hedge but not sure what makes up the hedge. Will get some photo's tomorrow and you can maybe tell me…?

In fact, as you don't require regs, have you considered a raft with thickened edges?

Nope, but only because I don't know what that involves…! Could I do that and still get 100mm of kingspan underneath for insulation, and ensure dryness etc by taking the DPM inside the clockwork?

Cheers
Mark

 

[Wizard9999]

Oh. Based on title had expected pictures of holes in the ground!

 

[Rob]

planned....not actuals :eusa-naughty:

 

[TrimTheKing]

Ah sorry chaps, unintentional misleading there. Fear not though I expect to break ground in the next couple of weeks when the weather improves and I've bottomed out a few of these questions...

In the meantime I'll be enjoying everyone else's labours!

Cheers
Mark

 

[Mike G]

In fact, as you don't require regs, have you considered a raft with thickened edges?

Nope, but only because I don't know what that involves…! Could I do that and still get 100mm of kingspan underneath for insulation, and ensure dryness etc by taking the DPM inside the clockwork?....

Yes, but it gets seriously complicated, with steps and toes. You might be better off sticking to foundations and and oversite on second thoughts.

If you are building hard up against a hedge, then even for a footing not required to meet the regs you should dig below any roots. If that forces you down to 1.2m or more, so be it. You can step the excavation, so that as you come away from the hedge and its roots you can bring the bottom up to 900 below ground level, but you must do any steps a metre or more away from a corner.

 

[TrimTheKing]

Thanks Mike

I will draw up some plans over the weekend for review (usual caveats understood) and will then modify as and when I get under way.

Hope you've had less snow than us over night otherwise you'll have some bailing to do and zero chance of getting and roof work done...

Cheers
Mark

 

[Mike G]

We've got an inch or two. No chance of working at height. Much too dangerous. I'll find something to do inside today...........I bought some flooring yesterday so I'll start the upstairs floor. Maybe make a temp. star as well.

 

[Wizard9999]

We've got an inch or two. No chance of working at height. Much too dangerous. I'll find something to do inside today...........I bought some flooring yesterday so I'll start the upstairs floor. Maybe make a temp. star as well.

No snow in north Hampshire . Kids not happy and I was hoping to be able to work at home on the basis of train chaos.

Given where you are located Mark presumably you won't be able to break ground until the ground has thawed around March.

Terry.

 

[TrimTheKing]

Maybe make a temp. star as well.

Wow! Have you got the space, materials and gravitational resources required to undertake such a challenge???

Cheers
Mark

 

[RogerS]

Maybe make a temp. star as well.

Wow! Have you got the space, materials and gravitational resources required to undertake such a challenge???

Cheers
Mark

Horizon had a good programme all about making a star on earth the other week.

 

[Mike G]

I blame the carpal tunnel syndrome. I can barely feel the keys anymore.

 

[AndyP]

Maybe make a temp. star as well.

Wow! Have you got the space, materials and gravitational resources required to undertake such a challenge???

Cheers
Mark

Horizon had a good programme all about making a star on earth the other week.

Was that the interview with Simon Cowell?

 

[RogerS]

Wow! Have you got the space, materials and gravitational resources required to undertake such a challenge???

Cheers
Mark

Horizon had a good programme all about making a star on earth the other week.

Was that the interview with Simon Cowell?

Oh very good :eusa-clap:

 

[TrimTheKing]

Okay so now the holiday is out of the way and other garden projects complete to satisfy The Management, I can now crack on with the planning for my 'shop.

After previous discussions with Mike on head height etc here's what I've come up with to maximise the headroom inside without going too far down and having to excavate too much material.



So basically the whole thing looks like this:

1. 1000mm * 450mm trench
2. Concrete poured to 500mm deep
3. 1 course of trench blocks (300mm wide)
4. Facing bricks, 100mm insulation in cavity, normal blocks internally
5. 150mm hardcore, 25mm sand blinding, 100mm celotex or equiv, 100mm slab pour.

Plan is to have rebar in the foundation and mesh in the slab.

DPM is the red line with the plan being to lie it on the sand, over the single internal brick, lay block course on top, take DPM up and over the block then next block laid on top. That way any water in the cavity is pushing the DPM against the block and not away from it internally.

Ref 4, do I need 150mm hardcore or is 100mm enough?

So am I there? Anything I've missed or done completely stupidly? If so then I can change, if not then I can start getting BoM together and get quotes.

Cheers
Mark

 

[AndyP]

when the weather improves

who are you trying to kid If you wait for the weather, it is June already, you will never get started.
My MIL is often saying "rain in the morning never stops the pilgrim".

 

[TrimTheKing]

Eh? Which post have you quoted that from Andy???

Cheers
Mark

 

[AndyP]

The one back in January Your optimism shining through again.

Ah sorry chaps, unintentional misleading there. Fear not though I expect to break ground in the next couple of weeks when the weather improves and I've bottomed out a few of these questions...

In the meantime I'll be enjoying everyone else's labours!

Cheers
Mark

 

[TrimTheKing]

Ahhhhhh, thought I had written something I then couldn't see!

Yep weather all good now and I'm hoping to start the footing digging next week. I need to start it by hand until I've located all the buried cabling then once I've found those I will get the digger in for some fun! :eusa-dance:

My biggest concerns right now are making sure my construction looks sound then I can get quotes and get stuff ordered ready for when my builder returns in August.

Cheers
Mark

 

[Wizard9999]

Mark

Starting on the basis that I know nothing, treat my thoughts accordingly.

If I read the diagram correctly, the red line in the outer skin one and a fraction bricks up is the DPC. The DPM comes from under the slab and wraps over your first block as described in your post. If this is correct my question would be why will water not go through your bricks belowthe DPC, through the insulation and then through your inner block skin immediately above where you DPM wraps over?

Don't you at least need the DPM to be wrapped over above the level of the DPC, at least that way the water would have to go uphill to make it into the building? Surely it would be even better to run the DPM up between outer skin and insulation and then lap it under the DPC in the outer wall, then you will have a waterproof barrier running under the slab and up the outer wall, so there is no gap for water to get through the wall and into the building?

Regards,
Terry.

 

[TrimTheKing]

Hmmm, I think I might have missed something when re-jigging the diagram the other night. The DPM and DPC should be level so I think I missed out another brick course under the blocks to bring the courses level.

Cheers
Mark

 

[TrimTheKing]

Chaps

A corrected diagram as per Terry noticing my c0ck up



So anyone got any comments as it's been very quiet when I've asked? I'm basing these off previous drawings by other on here, so I think they're okay, but could do with someone, telling me whether there's anything glaringly missing or wrong. :?

What I'm looking for is validation on whether my construction proposal looks correct,

1. Whether there's anything fundamentally wrong with using 2 brick courses under the blocks to bring the level top?
2. Whether the underground bricks need to be engineering bricks or can they be the reclaimed ones I've got for the rest of the build?

Cheers
Mark

 

[9fingers]

I guess you need to ping Mike for an expert view.

My 2p based no no firm knowledge or training!
Brick courses under blocks should be fine. Bricks and block are often mixed horizontally and vertically to simplify coursing
I would use a low absorbency brick below ground. An engineering brick would fulfil this as would other sorts of brick.
At least the bottom foot or so of cavity insulation would be best to be some sort of closed cell material to be absolutely sure the DPC is not bridged due to differing levels of DPC in each leaf.

I've seen drawings where the underfloor hardcore went down to the footings around the walls. No idea is this is essential or not?

HTH

Bob

 

[Mike G]

Sorry, I've been so busy (and tired) that I've not really being paying attention.

The most obvious thing, Mark, is that your DPC must be 150mm (2 brick courses) above the finished ground level, at a minimum.

Below ground you can use any old cheap regrade bricks, flettons, stocks, whatever. No need whatsoever for engineering bricks. There is no problem using as many courses as you like, but the standard thing is for the top of a brick (or block) course to be the top of your concrete: you use it as permanent formwork. So, to design your section you can either set your top-of-slab level and put a top-of-brick there, then work down from that to arrive at a top-of-foundation depth........or if the slab level is less critical, work from the top of foundation level and go up in brick courses until you arrive at a level which is OK for your slab.

I can't remember.....is this decent ground, and you are planning to do a ground-bearing slab? It's only a little more complicated if you have to do a suspended slab, bearing on the foundations.

 

[Wizard9999]

Mark

Did you ever establish what your hedge is made up of, likely root depth, etc? If I recall you are building pretty much right up against it and that was an early variable in your design that I don't think was ever settled in the thread.

Terry.

 

[Wizard9999]

Any progress Mark? If you're not careful autumn will be upon us...

Terry.

 

[TrimTheKing]

Hi Terry

Sorry I've been quiet on here recently as ben off with the kids and had loads to do around the house etc.

Yes I took Mike's advice and modified the design to take into account the brick courses etc, will post new diagram later. I have also been busy over the past couple of nights starting to tear down the shed ready for preparing the footings.

The kids are at Grandparents this week so I am working in the study during the day then as soon as the hooter goes I'm out into the garden for another few hours of demolition. Have been taking pics and will start a new thread on it later when I have a bit more time.

My builders are away until the start of the school year so my plan is to have footings and slab in place by the time they return in time for them to start putting the bricks up…

Cheers
Mark

 

[RogerS]

Any progress Mark? If you're not careful autumn will be upon us...

Terry.

What do you mean 'autumn will be upon us'? It's been upon us for the last six weeks!

Mark...essential you plan in SBT (serious beer-time) in the garden while the children are away!

 

[TrimTheKing]

Evening all

Well after a long hiatus, finally having finished the playroom in time for Christmas and getting various family drama's off the plate, I'm back to planning the workshop.

I'm working on the foundation and slab details that I was on before, and have come full circle in deciding I probably agree with Mike's early assessment that I have more than enough headroom by keeping the slab at floor level so why am I d!cking around digging down! :lol:

Mike - This look okay to you now…?



With that in mind I'm just going to go with Mike's detail of having the DPM come up inside the cavity and tucking in at DPC level, but one thing I can't get my head around is how you did this bit Mike…

http://thewoodhaven2.co.uk/viewtopic.php?f=26&t=368&start=750#p11805

Can you try and talk my feeble brain through how this 'present wrapping' technique happened…?

Cheers
Mark

 

[Mike G]

Hi Mark.

I composed a lengthy reply to this earlier today, only for the internet to go down (it's windy: that's what happens) and I lost the whole thing.

Without knowing the build-up of your proposed floor I couldn't really comment on the location of the DPM. However, I can say that it is usual to have the DPCs at the same level in the inner and out skins (obviously at a min of 150 above finished ground level). I would also point out that laying blockwork directly onto your concrete foundation doesn't leave you any great margin for error in the accuracy of the top of the concrete. If you get some lumps in it, it's difficult to adjust with blocks. I generally show a course of bricks at the bottom to allow for easy adjustment. Flettons with a big frog are easily chopped a bit if the concrete is too high locally.

The threshold detail is simple, but works better in theory than practice. You just make a straight vertical cut in the vertical DPM at the door locations, and lay it over the brickwork below the threshold. Then simply drape your DPC down the side of the door openings, along the brickwork under the threshold, and up the other side, such that the DPC is unbroken. I can't see why you should have damp in this area, but if you are worried by what looks like a vulnerable detail, you can always slap a bit of black gunk (Black Jack, Synthaproof, etc.) on the masonry (within the cavity) in the area.

Tell me what your proposed floor construction is again, so I can comment on that.

 

[TrimTheKing]

Hi Mike

Thanks for looking. Please see below a closer annotated view of the floor proposal.



For a number of reasons including laying and concrete costs and ease I read that using trench blocks as a bottom layer rather than the equivalent concrete was an acceptable route, but if you tell me otherwise then I'm happy to modify it as such, just need a pointer in the best direction in terms of what layout to go with underground.

Happy to bring the DPM/DPC internal level with external but I guess I need to finalise what's below that first to get coursing right. One thing I wasn't sure about was whether it's okay to use blocks underground or whether it needed to be bricks, even if it was any old kind as you advised previously.

Thanks in advance.

Cheers
Mark

 

[Mike G]

There is an oddity with your drawing, in that you label the slab and Celotex as 100mm thick, and yet show them the same thickness as a brick.

It seems to me that you have the top of your foundation at 675 below ground level. This is unnecessarily deep. Bring that up to 500 below FGL, then start with a course of bricks, and then blocks after that before swapping back to bricks at just below gnd level. At the same time, bring your finished floor level up 50mm or so (depends on coursing), otherwise you really will have damp issues at your threshold.

Is this building Controllable? (ie do you need to comply with B Regs?).

The build up of your floor looks fine, depending on your answer to the drawing problem in my first paragraph.

 

[Wizard9999]

Mark

Glad all the family stuff now in hand and that you are able to turn your thoughts to this again. Can we get excited about a spring build :eusa-dance: ?

Terry.

 

[9fingers]

Mike, IIRC, Mark was trying to get as much working headroom inside the workshop without having to take the eaves up higher than XX, hence the subterranean floor level.

Bob

 

[Mike G]

I know Bob, but he has massive headroom. More than me. Playing with 50mm at floor level is unnecessary, and asking for problems.

 

[9fingers]

I know Bob, but he has massive headroom. More than me. Playing with 50mm at floor level is unnecessary, and asking for problems.

But he is 6'3" according to another thread today :lol:

Fairy nuff, I'm sure Mark will take your wise words on board.

Cheers
Bob

PS just waxing the tables on my new planer after adjusting the roller pressure etc. Did you ever get your planer feed problems sorted out?

 

[RogerS]

I know Bob, but he has massive headroom. More than me. Playing with 50mm at floor level is unnecessary, and asking for problems.

But he is 6'3" according to another thread today :lol:

....

But that's only when he's wearing his stilettos. :lol:

 

[TrimTheKing]

There is an oddity with your drawing, in that you label the slab and Celotex as 100mm thick, and yet show them the same thickness as a brick.

Yep! You're not wrong Mike, not sure what's happened there as that wasn't intentional…! I will adjust the drawing to reflect what should be there…

It seems to me that you have the top of your foundation at 675 below ground level. This is unnecessarily deep. Bring that up to 500 below FGL, then start with a course of bricks, and then blocks after that before swapping back to bricks at just below gnd level. At the same time, bring your finished floor level up 50mm or so (depends on coursing), otherwise you really will have damp issues at your threshold.

Will do, thanks.

Is this building Controllable? (ie do you need to comply with B Regs?).

Nope, but I am still undecided as to whether to go down that route anyway, just so that it is fully signed off should I ever come to fell and want to advertise this as a granny flat or similar…Any opinion on that, or am I making life more difficult than it needs to be? I am planning on building it to BR standards as it stands, so it is fully compliant with the local regs, if for nothing else than I have the best building I can, but do I really need to go the BR route, I don't know…?

Here's the adjusted diagram..



Given coursing etc I think this is as close as I will get unless you have any other suggestions. I have thickened the slab slightly just to bring the top of the sand and the top of the slab level with courses to enable tamping as you suggested and also to mean the DPM can take the simplest path through the cavity.

How's that look?

Cheers
Mark

 

[TrimTheKing]

Mark

Glad all the family stuff now in hand and that you are able to turn your thoughts to this again. Can we get excited about a spring build :eusa-dance: ?

Terry.

Hi Terry

Thanks for that.

Outside chance of May build, but more likely August/September. My builder can possibly do May before he goes back to Poland for the summer, but that also depends on how much cash I can free up for him to do, and how much I need to do myself to keep costs down.

Realistically, we're probably talking the latter with me using summer to do the groundworks and lower courses with another builder mate who will help me for beer and BBQ's, then have my Polish chappie whizz the bricks up later on.

Hoping to do the roof myself to as previously mentioned so once I have this lower section sorted I will hopefully (assuming the offer still stands) take Mike up on his kind offer to spec up the roof for me…

Cheers
Mark