What's involved in a DIY Loft Conversion - any useful guides

[405 TD Estate]

Hi,

I have a nice large loft in my end-of terrace house which would make a lovely bedroom with an on-suite bathrom. I don't want to build out of the roofline just put some windows in. The stairs I would like to run off the landing (a proper staircase) which runs parallel to but above the original staircase.

So what's involved for the DIY'er?

Also it is worth doing it to building regs etc or just do it to my satisfaction (I would want to make sure there is a decent means of escape and no problems with damp etc)

My thoughts so far are :

I need approval to convert the loft though there is a possibility it is exempt?

I need to find all building regs relating to this - I would appreciate if people could give me pointers

The difficult bit will probably be the floor - Obviously It will need strengthening but do you have to take the roof off to get large beams in? How do you do the calculations?

Any useful guides 'how to's' would be good.

[Ron Lowe]

The structural issues are the paramount ones in the first instance. I'd STRONGLY reccomend you get a structural engineer involved at the design stage. TBH, I'd get an architect to do the planning and to subcontract a structural engineer.

There are several structural issues.

Firstly, if your roof is made from lollipop sticks ( like many are ), then there will be a bunch of internal bracing timbers in the loft, which will need to be removed. The load taken by these will need to be transferred to alternative structures. This may involve steelwork A-frames, or timber re-inforcements, limiting the width of the new room to accomodate some bracing behind the lie-ins, or total roof removal and replacement.

Then there's the floor to worry about. The existing timbers will not be adequate for floor loading, most likely. The solutions vary from stiffening the existing timbers, steelwork, additional verical support installed inside walls in the floor below etc etc.

Then there's insualation specification

Then there's all the building regs around bathrooms: Ventilation, drainage, etc, etc.

The design of a loft conversion ig in general not a DIY issue, although much of the actual work could be.

Building controll will *certainly* need to be involved in this.

Please understand that you are undertaking a serious structural alteration to the building, and this has serious safety implications if done badly.

There is no website that we can point you at that explains it all easily for the DIYer. It's beyond that. ( the design parts, I mean, not the actual work. )

[405 TD Estate]

I found this :

Bath Council's Building regs or interpretation of them - very useful

Any more practical pointers are welcome though....

[Ken H]

How does the law define a "habitable room" (in the loft)? I boarded my loft out back in 1993. I was careful to make the loft ladder/stair removeable (due to some clause in the regs which I forget). The two Wickes' skylight windows I put in the roof in the roof are way above the height-above-floor level of the current regs. Will this run me into problems when I sell the house?

Ken H

[John Rumm]

Well in blue peter tradition, here is one I did earlier:

Also it is worth doing it to building regs etc or just do it to my

Doing it with full building regs approval is an absolute *must*. Otherwise you will run into all sort of potential problems later.

Looking at it another way, there is nothing that onerous about doing it by the book (the regs regarding loft conversions are actually quite sensible and well worth doing), so you may as well.

Unless you live in a conservation area or a listed building, or plan to make dramatic changes to the roofline or the road facing side of the roof, you are unlikely to require planing permission.

All available here:

The difficult bit will probably be the floor -

I was pleasantly surprised to find that in reality it was not that difficult.

If you are not adding dormers then you can probably do most of the work from inside the roof space. You can remove a small section of tiles at a suitable place on the front or back of the building that will allow you to insert the longer beams etc.

How long is a bit of string? See my site to more guidance on this. There is software available that can do all the required sums, but you do need to do enough research and reading to know what information to feed in first. Otherwise it will just help you design something wrong more quickly!

[unknown]

If somone wants your house they'll buy it. If they start getting anal about regulation this and regulation that don't sell it to them, someone else will be along to buy it if it's at the right price in the right area etc etc.

IMHO.

[manatbandq]

The more you do (floor, lights, windows, insulation, etc), the more of a grey area it becomes. Just having a removeable ladder does not prevent the room being "habitable", according to my local authority. Only your local BCO can give you *his* interpretaion of the regulations.

MBQ

[405 TD Estate]

sure I print it out and put it in the 'loft' folder.

Where are you? The style of the bay wondows looks like Coventry...

[John Rumm]

Ta!

[somebody]

In message , 405 TD Estate writes

[snip]

I'd generally agree with the advice you've had so far, have plans drawn by an architect who should instruct an engineer for you. These should be submitted for approval by building control, and the work done under their watchful eye.

The calculations will be part of the engineers remit. If you're going to do it properly through building control, IME it doesn't matter whether you can do the calculations, it matters whether you are qualified to do so.

My only 'tip' ...

If you're going to be putting in any steel work, consider how it will physically be fitted. Three steels went in for our loft and typically each would have been inserted through the building from outside. You cannot fit a steel between two walls without knocking right through one of them.

For two of the steels this would have meant a big crane 15m away at the road. With the beams at 200Kg each, probably quite an expensive crane on day hire.

For the third beam it would have meant removing the conservatory roof.

I asked the engineer about cutting/plating of the steels - he looked at me as if I was mad ... "extra cost at the fabricators". The benefits though are having steels which are reasonably man manageable, you can work in your own time not to a schedule with equipment on hire, less disruption to the whole building etc.

Hth Someone

[405 TD Estate]

What - Do you mean cut the beams so you can get them up the stairs and re-join them once there?

[405 TD Estate]

If all the beams run in one direction then working out strength / deflection should be easy myself .

The problem would be how strong to make them?? I.e. whet woudl you assume for worst case flor loading?

Maybe 12 adults all stood in the centre of the room?

If anyone knows the beam type and dimensions and the number of beams used (or spacing apart) and the floor space I could back-calculate the strength/flexibility of their floor and assuming it was build recently and assume this strength is sufficient (as it will heve passed building regs/approval)

[somebody]

In message , 405 TD Estate writes

Sort of...

One beam in a kitchen ceiling for a new load bearing wall - that went up the stairs, inserted into the floor space from above and then bolted together in situ.

Other two beams to replace the roof purlins were winched up the scaffolding and into the loft through a new gable end window. They were then inserted into position at both gable ends and bolted back together.

It will very much depend on whether you need any steelwork and where.

Having them cut and plated achieved a number of things...

- reduced weight to make them (in my case) man handlable.

- allows for insertion into two opposing walls without knocking right through an outside wall.

- no need for a crane

Hth Someone

[John Rumm]

For a domestic floor with joists spaced on 400mm c/c, you would often use a loading of 0.8kN / m applied as a uniform load along the joist.

Depending on what other dead loads you impose on the floor, you may also have to take account of point loads in addition to the uniform ones. For example it would be quite common to include dwarf walls toward the eves in a loft conversion that does not include a dormer. The weight of these would then appear as a point load on each floor joist. If you say in addition took our a purlin that was used to help support the rafters, and replaced this with a dwarf wall, then the wall would become load bearing, and not only would its weight be placed on the floor joists, but so would be a proportion of the roof weight.

This was one of the things I alluded to in my original post. Doing the calculations is not that difficult in many cases, but selecting appropriate data to base the calculations on can be more difficult and is obviously fundamental to arriving at a useful result.

Well, the normal spacing for floor joists is 400mm centre to centre. The type of beam required will depend on the length and the loading[1]. The simplest beam is a wood one made from ordinary C16 constructional grade sawn timber. There are then a number of additional measures that can be taken to increase the strength of the beam as required to meet the performance requirements. These include:

1) Increasing the height and width, 2) using a higher stress grade of timber like C24, 3) using a pair of beams bolted together, 4) constructing a flitch beam (pair of wood beams bolted either side of a steel plate). 5) Using steel sections in place of key beams

Designing your floor to have as many beams constructed using methods near the front of the list will help keep costs down, and maintain workability and speed of construction. However you may also need to take into account headroom, which can dictate more exotic construction to keep floor joist depth down.

[1] Building regulations stipulate the maximum amount of deflection that is allowable in a floor joist (typically up to 0.003 times its length, or 14mm whichever is smaller)

[Tony Bryer]

You can have the beams cut into three and then bolt the sections together when back in the loft. Some loft conversion contractors prefer to do it this way as it saves a crane, but against that there is the cost and time of going down the splicing route.

[Charlie]

the alternative I believe is to fit fire doors throughout your house.

Could be cheaper than:

1. Moving the skyligh windows
2. Potential decrease in value of your house due to no building regs.

Just my thoughts!

Charlie