Help needed with flat shed roof

[Shabs]

I have just built the walls from concrete block. Now it is time for the roof. What i was planning was to use a 4x2 frame screwed sideways parrallel to the sides of the shed. i was then planning to use 4x2 upright screwed into the parallel frame at 18 inch centres, which is at the centre of each block to form the base for a flat roof. on top of the "joists" i was going to use the chipboard floorboard large sheets that fit together like cladding with sealer and felt on top.

Is this a good way of doing a flat roof and should this last quite a long time or is there another way of doing a flat roof.

Any comments greatly appreciated.

[Grunff]

Can you slope it just a little? 5 degrees slope makes all the difference to a 'flat' roof. If you do slope it, make sure the slope is parallel to the felt joins.

As for material, exterior grade ply would be a much better choice than flooring grade chipboard.

[Pete C]

Hi,

EPDM rubber is worth a look, also 'OSB' would be better than chipboard/compressed weetabix type stuff.

cheers, Pete.

[Shabs]

For the slope and it being parallel to the felt joints, if we take the keyboard for example as it slopes, ie higher at the top than the bottom.

Does the felt have to therefore run sideways, as the keys do, and not from top to bottom?

[Grunff]

No, the felt would run from top to bottom. So you'd stand at the top, with your roll of felt, hold onto one end, and unroll with gravity. The problem with running the felt sideways is that there is more chance of water getting in between the felt joins.

You can run it sideways, but if you do make sure you overlap the felt by a couple of inches at least, and that the upper strip of felt (the one covering your qwerty row) sits *on top of* the lower strip (the one covering the asdfgh row).

I personally hate felt roofs. Box profile steel is so much nicer to work with, and lasts 25-40 years without any maintenance. You can use it either on its own, straight onto the timber frame, or on top of ply to reduce condensation.

[N. Thornton]

chip is fine until the roof covering leaks, then by the time you get round to fixing it its had it. OTOH its very cheap.

NT

[Shabs]

The size of the roof for the shed as i have measured it is approx 18ft x 7.5ft. I will be using 2 inch of the 4x2 on one end and 4inch of the 4x2 on the parallel end to create the slope.

Excluding the timber frame which i have already bought, does anyone have any idea of the likely costings together with felt if needed with regards to the different materials as suggested by various users.

Thanks in advance

Chipboard - £

Exterior grade ply - £

OSB - £

Box profile steel - £

EPDM rubber - £

[Grunff]

You don't ask much, do you? ;-)

You need 5 sheets of 8'x4' if going for sheet/felt, or 3 sheets of 1mx6m box profile.

Don't know about cost of felt, haven't bought any in 10 years. Don't forget the sealant.

[Pete C]

Hi,

Thinking about it EPDM might be a bit overkill for a shed if the contents aren't that valuable, and you're likely to move within 10 years. If that's the case nomal felt over OSB or shuttering ply would do.

cheers, Pete.