Basement structure detailing

[Alan Ambrose]

Hi, I'm looking at my basement detail - particularly the part where the basement wall joins the house walls. I'd like to have both a traditional brick plinth (e.g. 1st image) and some lightwells into the basement - although the detailing to accomplish both looks a little troubling (3rd image below). I can see that if I lost one or the other (so that the support for the plinth didn't obscure the lightwells) life would be easy . I've based my current thinking (3rd image) re the support for the brick plinth largely on this MBC detailing (2nd image) - where they cast a fairly non-structural ringbeam to support the brick plinth into some EPS channel which is itself laid on MOT. I will have an SE design the RC basement and an oak frame co design/make/erect the frame - but I may need to do my own thing on the insulation and cladding and also the interface between the topsides and the basement. Anyone have any thoughts? Ta, Alan

 

 

[Thorfun]

We were originally having some light wells for our basement but eventually decided it added too much cost and complexity. Although we do have a basement courtyard for a secondary escape stairs so that is, in theory, just a big light well!

[Gus Potter]

On 12/12/2023 at 16:16, Alan Ambrose said:

I will have an SE design the RC basement and an oak frame co design/make/erect the frame

I think you are approaching this in the wrong way. You are trying to achieve savings buy the division of parts.

 

Lets put this another way.. you can buy a car complete for £Y or the parts and assemble it yourself for £ Y.. but unless you know what you are doing Y will always cost you more than X.

 

Get your SE in now to guide you as to how you marry all this up.

 

I would charge you about £1500 quid to put you on the right track.. sounds a lot but I know I could save you much more and easily cover my fee.

 

I know you may think this is a lot. But a good trademan will cost you £ 1.0 to 1.2k  a week, all I need to do is save you a week and a half of labour and I'll have washed my face.. then think about what I could really do for you? I could give you pointers and you can play to your hearts content on your insulation.. we would discuss it all and if I thought you were making an error I would pipe up and say.. hey I think this is wrong .. what about doing it this way..that is good design is all about where we all work together. If you can find a local SE that knows the local contractors.

 

If you have a basement then you are into tricky terratory. You could blow tens of thousands if you make the wrong play.. and that also means if you tell you designers that is what you want.. and if you are too cocky they will just give you what you want as it is your money!

 

I love your space frame concept, @Kelvin has a stunning house with a space frame for example. Your passive house goal.. love that too .. your basement.. that is where it could all go wrong unless you get a handle on the SE design early on. You need an SE for example who is going to stand up to the TF designer, the slab designer and the basement designer on your behalf. What you are doing needs good technical support leaving you to make the fundamental financial and overall design decisions.

 

I know you want to do your own thing.. good for you coming on BH as you'll get loads of free advice from folk that have been there, made mistakes and can tell you.. don't do this!

 

All the best and keep posting.

 

 

 

 

[Alan Ambrose]

Where's @Bitpipe when you need him? 

 

Gus, I think you might be right, I could do with some proper advice on the bits that fall between. That option hadn't actually occurred to me, duh.

 

I'm not mainly trying to save money (as soon as you say 'oak' you mostly lose that battle) but to get the best job done I can. I think oak frame with a basement is a bit of a niche - not exactly rocket surgery, but not mainstream either.

 

Let me PM you if I may.

[Russell griffiths]

@Alan Ambrose

ive only looked at this for 30 seconds 

but something doesn’t look correct on drawing 3. What part of the structure is actually load bearing, as you have the Larson truss sitting on the non structural plinth wall, if the Larson truss is structural then doesn’t that have to go down to the basement wall, or floor slab, so is the oak just for show ?

 

a large oak frame was put up by my neighbour recently and his kit came clad in sips panels, oak was the structural element and the panels did the insulation side of things. 

I was very impressed with the fit and finish, it was a high end build. 

 

It looks ok to me that you have two houses there one inside the other. 

 

Is the oak the structure or is it the larson and the oak is for show. 

[saveasteading]

18 minutes ago, Russell griffiths said:

@Alan Ambrose

ive only looked at this for 30 seconds

but something doesn’t look correct on drawing 3. What part of the structure is actually load bearing

Likewise. It didn't make sense to me, so I assumed this was more a specification/ guidance than showing real life detailing.

[Alan Ambrose]

>>> as you have the Larson truss sitting on the non structural plinth wall

 

This is structural oak frame with the cladding hanging off it, like your neighbour's. You'll see that the oak frame bears directly on the basement wall. My understanding is that's what all new oak frame houses are like now. You're right also - there should be a bigger gap between the truss and the plinth just to make it clear that the plinth is not load bearing.

 

>>> I assumed this was more a specification/ guidance than showing real life detailing.

 

This is a design sketch with the objective of making sure the main design blocks hang together and that the design decisions re plinth and lightwells can be firmed up. I have detailed stack-ups for the wall etc and, as it says, there are no membranes shown there. At this point, the detail is not that relevant though - I'm keen to see whether I can have the plinth and the lightwells. Obviously, I could omit both and make the structure simpler - but I would really like them if there's a way