Reinforcing Loft floor for heavier storage

[securitynewbie]

Hi,

My loft is currently being used to store small items at the moment. It has a proper staircase and I can walk upstairs without any problems.

The thing is though, I'm running out of storage space, so my next plan is to put large/heavy items in the loft. The only issue with it is that it has small 2-2.5in joists.

I would like your advise as to how can I reinforce these, so that they can take the weight of a desk, dismantled beds, and a few other heavy items as well as my own weight when I'm moving around.

 

[Doggit]

You can't really reinforce them; you'll need to run new joists alongside them, 6x2 minimum I'm afraid. Building regs would insist on 8x2. You've more than likely got 3x2's up there, but adding a say 4x2 on top, would require something like liberal application of Gorilla glue, and then screw the upper joist down with 7" screws every 10" at least, but whichever wasy you go, can you get the new joists up there in one piece.

 

[securitynewbie]

I don't see any problems in getting the joists up there, but I don't see why building regs would get involved as it's not going to be used as a habitable room as such.

 

[Mikefromlondon]

I have same situation as yours, I store lots of junk up in my loft. luckily my joists are 4"x2" and run every 16" to 18" interval, these joist are also supported by an internal load bearing wall, so my maximum span for joist is 12' and for most purpose these are coping well so far, and bear my weight easily. It could even support one other person as well without too much bother. The deflection is barely minimum.

I am also planning to reinforce existing joists, or alternatively go for a proper steel girder (RSJ) and new joists above the existing joists. You need to find out the span of your current joists and if there is any support underneath by any internal load bearing walls.

 

[Doggit]

Sorry to give the wrong impression, they are just the standard that you work towards. I converted my loft, and they wanted 6x3, but as the existing joists were only 12" apart, I managed to negotiate them down to 6x2, and then wished I hadn't - I was left with far too much spring. It was a 4.4m span, and I should have gone for at least 7x2.

 

[securitynewbie]

I have same situation as yours, I store lots of junk up in my loft. luckily my joists are 4"x2" and run every 16" to 18" interval, these joist are also supported by an internal load bearing wall, so my maximum span for joist is 12' and for most purpose these are coping well so far, and bear my weight easily. It could even support one other person as well without too much bother. The deflection is barely minimum.

I am also planning to reinforce existing joists, or alternatively go for a proper steel girder (RSJ) and new joists above the existing joists. You need to find out the span of your current joists and if there is any support underneath by any internal load bearing walls.

Sorry to give the wrong impression, they are just the standard that you work towards. I converted my loft, and they wanted 6x3, but as the existing joists were only 12" apart, I managed to negotiate them down to 6x2, and then wished I hadn't - I was left with far too much spring. It was a 4.4m span, and I should have gone for at least 7x2.

Thanks for your replies.

My loft also has a load bearing internal wall in the middle, so I can only assume that it would require shorter joists (approx 10-12ft??).

Doggit, don't be sorry, you haven't given a wrong impression.

I will try and take some photos and post on here. Now questions regarding joists:

1. If I got steel girder, how many would I need and approx how much would it cost?

2. How does one replace the old joists? Do you take out the smaller joist and then make a larger opening in the brickwork to slot the larger joint into or do you simply leave the old joist in and screw the new joist next to it/onto it? Any pictures or examples would be greatly appreciated.

 

[Mikefromlondon]

Unfortunately you cannot take out old joists even if you did it one by one, it would ruin your ceiling attached to it underneath. Unless you were prepared to put up new ceilings. You could run new joists parallel to existing joists, resting on top of the wall plate, (wall plate is a piece of timber that runs along the top of the wall, on which joists usually rest) However as you will be using bigger size joist e.g. 6x2 or 7x2, against your 2.5 or 3x2, the new joists may interfere with the bottom of your roof line, so you may either taper them off near the wall end as tapering it near this wall end where it rests on your wall plate may be OK and should not effect their strength, but this depends exactly how your wall plate and joists and rafters are arranged. In my place I have joists resting on wall plate, and then there is another piece of timber that runs across on top of the joists (so you may call it joist plate) unless it is known by other name, on which rests my rafters, so in my case if I were going for bigger joists, my joists will have to be narrowed down to 4" as the 6" joist won't tuck under this upper plate. In other words my joist will need to be cut down to 4" near wall end. Again this should not effect its overall strength. You could taper yours in line with your roof pitch angle towards the wall plate. You could also bolt new joist with existing joists as well but it is not essential though it would further strengthen its capacity and help distribute weight better.

As for your 2nd point, it is not how you described that a joist ends up going into the wall, it may do so on smaller things like sheds and garages, but on houses they use so called wall plate, that bears the weight of joists and rafters. This so called wall plate ( a long piece of timber runs on top of the wall and can be 2" high by 4" wide, it is almost same size as a joist but runs on its side hence the height is shallower than its width.

 

[Doggit]

If you have a load bearing wall in the middle of the house, then the jobs a simple (ish) one. You need to wedge a 4x3 beam with the 4" side upright down into the angle where the roof joists meet the ceiling joists, and fix it in place. You then fix joist hangers on to this to take the new joists. Set the hangers so that you leave about 1 or 1.5" above the ceiling floor, and as you put in the joists, you then need to set in wedges on the load bearing wall in the middle to level up the joists up as you go. Set the new joists alongside the old ones. And you should be fine. Depending on how good you are at leveling a floor - or depending on how long your spirit level is, set every fifth joist, and then the intermediary ones.

 

[securitynewbie]

Thanks very much for the help guys. I'm currently at work, but I'll get some pictures uploaded for you to take a look at.

Can you post any pictures/diagrams/guides of what you are describing as it would be of g great help for me to understand.

 

[securitynewbie]

Hi everyone,

Sorry for the delay. As promised, here are the photos of the loft. A few things to note:-

• The loft is approx 25 metres in length.

• You will notice that there are new joists (4x2) going across on top of the old floor joists. These are only in one section of the loft and the rest of the lof has only the 3x2 joists.

• There is a staircase running in the middle of the loft. One side of the staircase is what seems to be a load-bearing (solid) wall and the other is a hollow plasterboard version.

• The 3x2 joists seem to be going the whole length of the loft (25 metres), but I can't check because there are large chipboard flooring pieces screwed down. However I think that the joists most likely end at the point of the staircase, where there is an internal load bearing wall. If this is the case, then this would mean they are actually approx 12 metres.

 

[tony1851]

• The loft is approx 25 metres in length.

How big is your house??

 

[Doggit]

Having seen the pictures, I think I'd be out of my depth giving any more advice without being on site.

 

[Mikefromlondon]

I am sure you didn't mean to quote your dimensions in meters, they look more like in feet, than in meters .

Any ways the pictures aren't telling us any better. you also have a lot of black dust which i took all the trouble to hoover out, because of the dust we cannot really tell see much detail. the width on one of them is 2.5"(inches)

those new joist at 90deg across sitting on top of the existing 3x2 don't say much because we cannot see if these are being supported at each end, or just bearing more weight on the existing joists.

 

[securitynewbie]

Really sorry guys, as I was half asleep. Yes it's in feet and not meters.

The new joists are simply sat on top of the old ones. They have been screwed to the old ones and if you look at the first photo the are not attached to any wall or anything at each end.

The first measuring photo is of the new joists which are sat on top of the old ones, which is 4in by 2in.

The second measuring photo is of the old joists supporting the floor. It is measuring the height/depth of the old joist, which is 3 inches.

The third photo is again of the old joists supporting the floor and this time it's measuring the width which is definitely 2in and not 2.5in.

Please could you tell me exactly what you don't understand and what type of photos to take and I'll do these ASAP as well as provide you with a breakdown of any explanations.

 

[Mikefromlondon]

I will post some drawings later on I did on Paint, as I have also been looking into my loft space for heavier items for long term storage, and did not want to take a chance with ceilings bowing due to extra weight, a 4x2 joist running at every 14-16" with a span of 12 foot, is definitely not going to snap in half even if I one were to put a couple of car engines, breaking capacity of such beams is enormous, just one single 4x2 and 12 foot long joist could support a weight of a whole small car before it snaps, I have been looking on internet for breaking capacity of such timber beams, but have not found any information other than what is recommended by BC guidelines like what size to use and how far apart and over what length of span. The biggest problem is the deflection that can cause ceilings attached to it to crack and fall off.

Other things to watch out are weight of the roof tiles supported by props resting on joists, and the foundations, since all weight gets transmitted into the foundations, existing foundations may not be adequate, I also have a bay window, which don't transmit a lot of the weight, which means most of the weight from my loft floor goes into adjacent walls adjoining the bay window, so again if steel girders were used these can be hooked to side walls instead of the front and back walls thus shifting the weight of the new floor totally away from the front and rear foundations and placing it on side walls (walls between the terraced houses)