Underground Home cinema extension

leftylion

Active Member
Hey
Thought I’d share how I built my latest home cinema. We moved house and decided to build a double story extension on the back of the house. This was going to have a home cinema room upstairs instead of an extra bedroom.
May builder friend Steve, owner of Your Local Builders in Creswell, Notts, started but after a couple of days digging to find the original house footings it was becoming clear things were going to be difficult! The house foundations were 3.2m deep. We had to have two machines digging out due to the depth. This would have meant very deep footings and lots of concrete. The ground was falling in all over so this wasn’t looking good. Then one of the guys said ‘why don’t you just have a basement’! I immediately said yes, dig it all out and have an underground cinema! We got on with changing the planning permission but also carried in with the build. We took out 220 tonnes of soil, a lot of which had to be moved by wheel barrows from the back of the house to the front to dispose of. As you can see from the photos the house was exposed completely on one side!
The builders did an amazing job getting the one foot thick reinforced concrete walls in place, such a relief when done for everyone.
The builders carried on with the single story extension on top for the living room. With the brick shell and floor in place then we had a new problem, the pandemic lockdown!
we literally had just finished completing our kitchen as we had been living for a month in the bedroom and we had a small living area in it but we had no garden and an unfinished extension! Luckily for us the kitchen fitter, Tom, was extremely handy and agreed to work for us during the lockdown, he had been with us for five weeks beforehand. I laboured for him so between us we managed to get the cinema floor in, tank all the walls, fit doors, additional stud walls, the electrics and wiring, and the drainage system with pumps. We had two pumps submerged in the outside stairwell, one run on electric and another on top from a battery back up system. Expensive but essential. They were supplied by Pumps and Sumps Limited. They gave us the right advice and equipment. We fitted the thermal plasterboard and then I put in the aluminium trunking to house the led strip lights in the wall and ceiling. Luckily Toms dad was a great plasterer and agreed to complete that. We fitted in the window and spiral staircase and Tom made the curved wall for the living room access to the stairs. I got on with painting and carpets and completed the setup of the system housing the amp etc in a data cabinet with fans to keep the amp from overheating. I built in the shelving for my UHD collection and Hot toys and then was ready for the grand opening!!
I can’t thank the guys who helped enough for helping my dream come true. It truly Is amazing, 133 inch UHD visuals with 7.1.2 Dolby Atmos/DTS:X sounds.
Equipment list:
Marantz SR7012 AV receiver
Optoma UHD60 projector
Samsung UBD-K8500
Zappiti Duo 4K HDR media player
Logitech Harmony Elite remote controller
133 in Duronic Fixed frame screen
Kef T-series 101
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inzaman

Moderator
Wow that is awesome and an amazing project that no doubt took a lot of effort. Congratulations on the build, a basement is perfect for a home cinema imx as you do not have to worry about light control.
 

leftylion

Active Member
Wow that is awesome and an amazing project that no doubt took a lot of effort. Congratulations on the build, a basement is perfect for a home cinema imx as you do not have to worry about light control.
Thanks
Yeh, was tough but glad I did some of the things myself. You’re right about the light but there is a external door in the corner of the room near the screen but I made an insulated/soundproof board from mdf to cover it. It’s also easy to move in emergency. 👍
 

mb3195

Distinguished Member
An underground cinema would be on top of my list if I ever get round to having my own house built!! Top job 👏🏻👏🏻👏🏻
 

leftylion

Active Member
Some amazing pictures! Did they have any idea that the footings were so deep? Seeing the back of the house exposed like that is crazy. What a year you've had!
Hi. We new they would be deeper than normal but didn’t expect it to be as deep as they were. The architects and builders were really worried about the house being exposed, it was strange looking down from the top bedroom window! All
Worth it though in the end. We know we are extremely lucky to have this. 👍
 

Triggaaar

Distinguished Member
Hey
Thought I’d share how I built my latest home cinema. We moved house and decided to build a double story extension on the back of the house. This was going to have a home cinema room upstairs instead of an extra bedroom.
May builder friend Steve, owner of Your Local Builders in Creswell, Notts, started but after a couple of days digging to find the original house footings it was becoming clear things were going to be difficult! The house foundations were 3.2m deep. We had to have two machines digging out due to the depth. This would have meant very deep footings and lots of concrete. The ground was falling in all over so this wasn’t looking good. Then one of the guys said ‘why don’t you just have a basement’!
Wow! Best builder comment EVER!

The cost of adding a basement on usually makes the project a non-starter, but given how much work you were going to have to do anyway, what a fantastic solution. I'll have a good read of your thread, but it looks like they did a really good job with the structure.
 

kenshingintoki

Distinguished Member
how much does it cost to build a basement or does it already have to be there?
 

kbfern

Distinguished Member
Fantastic opportunity you took in creating this underground cinema and you will have perfect light control and the ability to listen at insane levels without bothering anyone. 😍
 

Triggaaar

Distinguished Member
how much does it cost to build a basement or does it already have to be there?
Well the one in this thread wasn't there.

For a new build with plenty of land around, it's not too bad.
For an existing build with neighbours close by - well, if you have to ask, you can't afford it :D (that certainly applied to my basement aspirations).
 

leftylion

Active Member
Well the one in this thread wasn't there.

For a new build with plenty of land around, it's not too bad.
For an existing build with neighbours close by - well, if you have to ask, you can't afford it :D (that certainly applied to my basement aspirations).
You’re right, you need extremely understanding neighbours and also dependant on your local planning office.
Also, costs depends on how well you know the builder. As mentioned in the post he is a good friend so did me a great price. I’d imagine it would have cost around £75k-£100k for the double story project. I paid just above half of that! And I did do a lot of the work myself.
 

Triggaaar

Distinguished Member
You’re right, you need extremely understanding neighbours and also dependant on your local planning office.
Also, costs depends on how well you know the builder. As mentioned in the post he is a good friend so did me a great price. I’d imagine it would have cost around £75k-£100k for the double story project. I paid just above half of that! And I did do a lot of the work myself.
Wow, that's some friend to have. I can't see from your post what you ended up having, apart from the cinema?
 

leftylion

Active Member
We had a single story extension on top of the cinema for our living room. I’ve put some pics on. We have a decent setup in there, 8k tv and Dolby atmos surround.
yeh hes a good friend! Saved me a fortune really.
 

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markymiles

Distinguished Member
Looks great. With land being so expensive always wondered why basements aren't more popular here. Your build doesn't look ridiculously complicated? I suppose it's much harder to go under an existing house.
 

leftylion

Active Member
No, not that complicated really. Just needed the architect to spec the correct reinforcing and concrete strength. Would be difficult to go under your house with different types of foundations etc. Only thing with it being underground is the extra for drainage and pump systems.
Probably one of the best things i have done though. I would advise anyone thinking of a cinema to look into it first. Obvious advantages are no problem with sound and light.
 

Praetorpwj

Active Member
That’s really great and definitely the best way to do a home cinema. I was going to create a new cellar space as part of an extension but the cost / m2 of space was going to be nuts especially if you wanted good ceiling heights.

Had to abandon in favour of a ground floor extension but I love the idea of it.
 

Praetorpwj

Active Member
Looks great. With land being so expensive always wondered why basements aren't more popular here. Your build doesn't look ridiculously complicated? I suppose it's much harder to go under an existing house.
There are not many companies who can do it especially waterproofing. You’ve got uncertainty as to what is in the ground especially if you’ve got existing drainage in proximity. Then excavation support, rebar and concrete, access etc. I have existing cellars and the idea was to connect into them from an existing access and it was still going to be twice the cost / m2 of a surface build.

The financials tend to work better in the South although build costs are even more expensive.

Still it works really well for home cinema especially if you can afford to build in good head height.
 

shodan

Distinguished Member
What an amazing and stunning build! Awesome! one question though..

How the heck did you get the sofa down there???
 

leftylion

Active Member
What an amazing and stunning build! Awesome! one question though..

How the heck did you get the sofa down there???
Thank you. For the sofa there's a hidden door in the far left corner that leads to the outside stairs. It does split down so just about got it in there. I did buy some lazy boy style seats but they didn't fit!
 

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