Loft conversion to dedicated cinema room

[Pulsar]

Morning,

I think it is about time to start documenting the loft conversion I've been planning in my head for nearly 2 years. I took the first tentative steps over the Easter weekend, gutting the room ready for the initial build stages. I'm creating this thread because I want to share my experiences with you guys, hopefully helping others who may attempt something similar in the future and to ask for advice and opinions on the choices I make. Here's a little background.

I bought the house I live in now in July 2007. It is a 3 bed 1930's semi-detatched, a world away from our first house (a 2 bed, new build end terrace) which came to us in quite a state. Since moving in we've been hard at the DIY to bring the main living areas 'up to spec'. So far we've replaced the kitchen and bathroom, totally ripped out the lounge and decorated the dining room. Every room in the house needs re-plastering as the original stuff is being held on by the wallpaper!

My wife fell in love with the house on first sight, and although we viewed loads of properties she was never swayed from it. I was less convinced as I had a better understanding of the work involved in renovating such a property, but the one thing that kept bringing me back was the loft! The previous owner had done a part loft conversion (a very small part) by cross battening the ceiling timbers and laying a chipboard floor, erecting studding to make some false walls and a ceiling and added a flight of stairs from the third bedroom to the loft.

None of the work was carried out to building regs and the loft wasn't sold as another bedroom, simply an accessible storage room. The insulation up there was very poor, the third bedroom was basically the same temperature as outside (not great in the winter) and made it unusable. My plan for the loft space was always to make it my ultimate dedicated room (I've had 2 before, but they weren't amazing by any stretch of the imagination) and now I'm finally in a position to realise this dream.

I'm lucky that the loft is quite generous with good ceiling height and full gable walls. There is only 1 structural timber that needs to be removed, but I've already taken advice on this and shall document it in later posts.

I've been messing with Google sketchup for a few months to get an idea of what I'm going to do with the space. I feel that I'm getting close to what the finished room may look like so I've attached some pics below.

[Pulsar]

In the pictures you'll see that I plan to split room into 2 sections. The covered part of the room will be a small landing (stairs not shown on drawing) and will contain all of the equipment for cinema.

The basic construction of the loft has 2 pairs of purlins. The inner (higher) pair are around 6ft at the top making the space between them very usable. The loft is around 22ft long and between the high purlins about 9.5ft wide. I'm going to take the room out to the second, lower set of purlins as I think it will make the room feel bigger.

I've shown a screen approximately 8ft wide with seating situated 1.25 x screen width away. The seating position is somewhat dictated by the location of the the supports for the higher purlins which transfer the weight down to a brick wall below. My original hope was to remove these supports to give greater layout flexibility, but after investigation I don't think it is feasible without massively increasing the work required.

The screen wall end of the room is the party wall and as such I've planned to build out a chunky 0.5m false wall to allow for sound proofing etc. I've also shown the walls either side of the screen angled in. This is because I plan to use all 'in-wall' or baffle mounted speakers to give the room a very clean look. I also plan to use an acoustically transparent screen with the centre speaker mounted behind it.

The room is going to be 100% dedicated to watching content from a projector, so I'm going to make a true 'black hole'. Current plans show all of the walls are going to be covered in a black velvet/alacatara type material - probably over foam pads to aid sounds reproduction. There's still plenty of research to be done here.

[Pulsar]

The first stage of the project has been to remove all of the studding/insulation that the previous owner stalled. I'm quite close to finishing this now and will soon start laying the new floor joists. Using span table found on the 'net, I've calculated that I should use 7"x2" floor joists at 400mm centres. These joists are going to laid perpendicular to the roof trusses, above them (15mm clearance) using joist hangers at either end and bearing on the brick wall that the purlin supports attach to. I'll probably do another drawing to illustrate this better.

The second stage of the build is going to be insulating the room. I've decided to use the PIR type rigid board insulation (Kingspan / Celotex) in a between and under rafter installation (40mm between, 40mm under at right angels). On top of this I plan to use a laminate of 2 plasterboards (possibly soundblock) with green glue or similar between. This will exceed building regs for heat insulation of a loft conversion and hopefully keep the sound at bay (both outside coming in and visa versa). Again I'm going to be seeking your help with this so if anyone has done similar then please let me know your experiences.

There is loads more to come on this, I'll get some pictures of the actual room taken today and will post them up later. I had better get started on the work now or it will never get done.

Cheers

Rob

[deansocial]

are you sure it will exceed b regs for heat insulation, as from memory you have to achieve 0.19 which to do that you have to have between 110mm and 120mm of board to achieve this dependant on rafter centers. Not sure what impact doubleboarding has on u value but sure it is not much.

Has it been calculated for the extra weight of soundblock board to go on the rafters

[deansocial]

as for the joists is there any supporting walls running across the middle of the loft so the joists arerunning the same way as the existing ceiling joists as that way you can drop them between and gain that extra room. It is normal to use 7x3 or 9x3 for this, if you have the room you can even use ji beams(the i beams with osb web) and they reduce the sound transfer.

If you dont want to mess around with chicken wire between the joists for fire regs you can use firefly with is a fire proof matting.

[deansocial]

oh and you have to change all your doors for firedoor to comply to regs aswell

[Pulsar]

Originally Posted by deansocial

are you sure it will exceed b regs for heat insulation, as from memory you have to achieve 0.19 which to do that you have to have between 110mm and 120mm of board to achieve this dependant on rafter centers. Not sure what impact doubleboarding has on u value but sure it is not much.

Has it been calculated for the extra weight of soundblock board to go on the rafters

Hi,

I think you may be right. I haven't done the exact calcs yet and need to find out the U value for the laminated plasterboard. Using the celotex calculator I will get a U value of 0.2 with 40mm between and 70mm under.

Haven't checked about the strain on the rafters, will have to take a look - thanks for suggesting it.

Rob

[Pulsar]

Originally Posted by deansocial

as for the joists is there any supporting walls running across the middle of the loft so the joists arerunning the same way as the existing ceiling joists as that way you can drop them between and gain that extra room. It is normal to use 7x3 or 9x3 for this, if you have the room you can even use ji beams(the i beams with osb web) and they reduce the sound transfer.

If you dont want to mess around with chicken wire between the joists for fire regs you can use firefly with is a fire proof matting.

Hi again,

There is a supporting wall in the middle of the loft, but the roof of the house projects below the height of the end walls making it difficult to support the ends of joists running in the same direction as the ceiling timbers. Just to confirm, when you're in a bedroom the ceiling angles down for the last 2 feet at the outside wall - hope this makes sense.

I have been considering the manufactured i-beam / web joists (posi-joists?) but thought it might be better to stick with simpler technologies. Because my joists won't be in contact with the existing ceiling timbers I hope they will be fairly good at not transfering sound to the room below. This is where I got the span / size requirements for the new joists.

Load-Bearing Walls And Safe Floor Joist Spans

I plan to lay new insulation over the existing ceiling timbers, between my new floor joists so it won't be in contact with the ceiling plaster below.

I'm not actually going through building regs for the work for a number of reasons, but I do want to comply with all of safety aspects wherever possible. Therefore I am really grateful that you've taken the time to post these questions / observations.

Rob

[Magslad]

Hi Rob

Have recently completed something very similar (albeit an all-purpose room rather than a dedicated home cinema) - loft conversion in a 1930's semi with the screen (plasma in my case) on the party wall.

Link to my build is in my signature below if it's of any help. Ours was done under full building regs which you've said you're not doing so wouldn't necessarily need to do all the little bits, but a few inital thoughts for you:

- Under building regs all doors to any 'habitable room' in the house (bedrooms, reception rooms etc) would need to be changed for an FD30 fire door. Not necessarily a problem for you now but might come up if you sold the house
- Building regs would also require a mains fire alarm system on a separate circuit (with 3 interlinked alarms on ground/1st/2nd floor). Again not necessarily a problem in terms of living in the house but may come up if you sold
- For insulation on the loft ceiling, we avoided Celotex/Kingspan as the depth required to meet building regs means you lose a fair bit of ceiling height. Like you, we have good ceiling height anyway so not necessarily a problem but I wanted the room to feel as spacious as possible. So instead we used a product called Triso super-10 (pics of it are in my build thread). Total thickness was only about 15-20mm but meets all the requirements. Goes on like a tent then plasterboard over the top. Our loft was finished in December and I've had the heating on once since then (the days we had the heavy snowfall), so definitely does its job well. Under the floor we used Kingspan as depth isn't an issue here given the joists
- False wall on the screen wall definitely a good idea, I did this as well. Only about 25-30cm depth, filled with Kingspan, but I've checked with our neighbour and she has never heard any noise coming through
- Are you building access doors/hatches in the purlin walls for storage in the eaves? May not be an issue for you but we were very glad we did this given that by converting the loft we lost one of our main dumping grounds! Didn't do anything fancy, just boarded out with simple lighting then 5 access doors around the room, amazing how much stuff we can fit in there out of the way

Just a few initial thoughts there, from your thread it sounds like you're pretty much on top of what you're doing but if you have any questions I'm happy to help in any way if I can.

Cheers
Dave

[deansocial]

tri iso super 10 is no longer accepted for loft conversiond as it does not have a bba cert. I have used it on 3 loft conversions when it was accepted but was old on the lastit will no longer be accepted and true to there word when asked on the next job they said no chance.

As for fd30 firedoors you can simply swap for a 35mm firedoor now rather that swap the frames like we had to before they came out.

you more than likely will have to strap the new floor to the ceiling to replace the binders than run across unless you are above that height.

When you put the flooring down it is now regs to have it go all the way into the eves for fire regs

Soundproofing the party wall is a must to meet regs aswell as is adding 50mm celotex to the gable end(assuming its not hipped roof)

[Magslad]

Originally Posted by deansocial

tri iso super 10 is no longer accepted for loft conversiond as it does not have a bba cert. I have used it on 3 loft conversions when it was accepted but was old on the lastit will no longer be accepted and true to there word when asked on the next job they said no chance.

As for fd30 firedoors you can simply swap for a 35mm firedoor now rather that swap the frames like we had to before they came out

Triso super 10 approval must vary depending on the local authority - I know for certain that it is still approved and accepted for loft conversions in our local authority (know of one last week that was accepted), and not aware of any plans to remove that approval.

We didn't have to swap any frames when we changed our doors either - we just needed doors that had the FD30 rating.

[sdemmery]

Hi Pulsar,

Good luck with the project, I am in the midst of loft conversion I have a thread here http://www.avforums.com/forums/membe...t-hearted.html if your interested. Im trying to keep it up to date, but its manic here at the moment. Its going to be a master bedroom but the bed (Now built must update my thread) is a wall bed which when up will give me a room of about 4x5mtrs

I contemplated a basic conversion without building regs in fact I even started the job, but then changed my mind & felt I just wanted to do it via the official route. I got concerened about the "what if" situations (i.e. what if we have a fire in the loft no regs would mean now insurance payout, what if someone becomes trapped up there etc) The basic conversion has now evolved into a full conversion including full width dormer & bathroom! I also hung up my hammer on this one & got a great couple of builders in who are doing the whole thing. This was really difficult for me as I have always done all my own work on my houses. Still leaves me more time for tinkering with my AV setup oh & decorating

I think most of the other posters have covered a lot of the reg requirments even though you are not going down this route, but one thing I havent seen discussed is head height. If anyone is thinking of doing a conversion you need a minimum of 2mtrs this was the killer for me as had to lower all my bedroom ceilings putting in a new loft floor/1st floor ceiling, basically the top floor was gutted & we moved out for a week.

All exciting stuff, we are now back in the stairs are complete & the steels are going in next week. Anyway if I can be of any help please just shout, I spent a fair time studying the regs myself Im no expert but I may be able to help.

BTW The required U value is 0.2 I believe a rediculously low value, kingspan or celotex on its own is unlikely to acheive this alone we are using a mixture of TLX (Thinsulx) & celotex or something like this. The TLX is very thin & expensive but is a seriously good insulator.

Looking forward to seeing your progress.

Stu

[sdemmery]

Oh forgot to say, to work out the timber spans you need to get hold of the TARDA span tables. They used to be free but I believe you have to pay for them now. PM me if you need them

To give you an idea we needed a min of 6"x2 of C24 rated timber and could not span over 3.5mtrs. we do have a 7mtr beam but this is a Flitch beam (two 6x2's with 10mm plate between)

Cheers
Stu

[Pulsar]

Originally Posted by Magslad

Hi Rob

Have recently completed something very similar (albeit an all-purpose room rather than a dedicated home cinema) - loft conversion in a 1930's semi with the screen (plasma in my case) on the party wall.

Link to my build is in my signature below if it's of any help. Ours was done under full building regs which you've said you're not doing so wouldn't necessarily need to do all the little bits, but a few inital thoughts for you:

- Under building regs all doors to any 'habitable room' in the house (bedrooms, reception rooms etc) would need to be changed for an FD30 fire door. Not necessarily a problem for you now but might come up if you sold the house
- Building regs would also require a mains fire alarm system on a separate circuit (with 3 interlinked alarms on ground/1st/2nd floor). Again not necessarily a problem in terms of living in the house but may come up if you sold
- For insulation on the loft ceiling, we avoided Celotex/Kingspan as the depth required to meet building regs means you lose a fair bit of ceiling height. Like you, we have good ceiling height anyway so not necessarily a problem but I wanted the room to feel as spacious as possible. So instead we used a product called Triso super-10 (pics of it are in my build thread). Total thickness was only about 15-20mm but meets all the requirements. Goes on like a tent then plasterboard over the top. Our loft was finished in December and I've had the heating on once since then (the days we had the heavy snowfall), so definitely does its job well. Under the floor we used Kingspan as depth isn't an issue here given the joists
- False wall on the screen wall definitely a good idea, I did this as well. Only about 25-30cm depth, filled with Kingspan, but I've checked with our neighbour and she has never heard any noise coming through
- Are you building access doors/hatches in the purlin walls for storage in the eaves? May not be an issue for you but we were very glad we did this given that by converting the loft we lost one of our main dumping grounds! Didn't do anything fancy, just boarded out with simple lighting then 5 access doors around the room, amazing how much stuff we can fit in there out of the way

Just a few initial thoughts there, from your thread it sounds like you're pretty much on top of what you're doing but if you have any questions I'm happy to help in any way if I can.

Cheers
Dave

Hi Dave,

I had read your build thread previously, but I've just been through it again. I like the sound of the Triso and have just been doing some quick reading on it. Is that all you have used as insulation on the rafters in the loft? How does it perform at keeping the noise in/out of the room?

I'm not planning on having any storage in the eaves as the room will go out quite wide not leaving much space behind for storage. I know I'll probably regret it later, but I've found it quite liberating to get rid of loads of the junk we had stored up in the loft. In the small landing room I plan on using some of the eaves as storage for the AV gear.

I'll check on my doors, just replacing all downstairs ones as we speak and they have the exact same pattern as the ones you have (oak veneer?) not sure on their fire rating though. I do plan to install mains powered smoke detectors too.

I guess many people say 'we plan to stay here forever' when justifying not going for full building regs and I would say the same. However it is not just this, I really don't want a window in the room which I believe building rags would require.

Cheers

Rob

[Pulsar]

Originally Posted by deansocial

you more than likely will have to strap the new floor to the ceiling to replace the binders than run across unless you are above that height.

When you put the flooring down it is now regs to have it go all the way into the eves for fire regs

Soundproofing the party wall is a must to meet regs aswell as is adding 50mm celotex to the gable end(assuming its not hipped roof)

Hi,

The new floor will clear the existing binders (just as they are 7x2) but I need remove them so will use straps to the new joists. Not sure if this will transmit much sound?

Regarding the new floor having to all the way to the eaves, I don't think I am going to do this. I plan to go within a few feet, but the height between the new joist and the rafter if I fitted a further joist would be only a few inches. Don't fancy giving that a go.

I haven't decided what I'm going to fit to insulate (both sound and heat) the party wall yet. Any suggestions welcome.

Not sure why I have to use 50mm Celotex on the gable wall, all of the other walls in my house are just plasterboard on to the brick. Will have to think about that one.

Thanks again for the advice.

Rob