Advice needed on replacing a rotten patio door cill

Hi all,
Can anyone give me advice/tips on how to replace my patio door cill without ripping out the whole patio door? I'm renting in Exeter and the patio door is in Swindon so its a fair trek back and forth to try and fix it so I'd like to get as much info as I can as I haven't done this before.

The wooden cill is rotten from the inside of the building, looks like a breach in the sealant between the cill and door let water and woodlice in (wondered where they were coming from) for years.

Scraping out some of the cill (from the inside) shows that the whole cill will probably need replacing. About a third of the cill under the patio doors has been scraped out, as I only had the weekend I wedged a stone under the void to hold the door up and temporarily sealed the exterior of the cill. You can see the mortar base with the damp proof coarse under it, some of the mortar on top of the damp proof coarse is breaking up as well.

I was going to try and chop out the old cill in sections wedging it as I went along, then get a new cill and tap it in from the interior to exterior and push the wedges out as I go along.

Though I am completely unaware of the size of cill etc, went to jewsons, they quoted a softwood cill 6"x3" at £21/m and it looked kinda chunky. The only other stuff they had was hardwood, in 6"x3 and 6"x2" at around £55/m !ouch! over £110 for a piece of wood!

I'd appreciate any advice, an idiots guide type steps would be even better, I intend to make the trip up this weekend to make a start.

Thanks in advance for any help

I don't know how you'd do this without removing the D/G from the subframe. If it's a standard 2 panel door with one fixed and the other sliding, you should be able to lift them out without too much trouble, but I wouldn't try it on your own - they weigh a ton(ish). All you'll have to deal with then will be the light D/G outer frame in the wooden subframe. the bottom cill is usually left to 'float' so cutting it out shouldn't be too hard ( you can drill it away with a spade but to cut through it). Things to watch out for :- rotton bottoms to the upright posts where they join the cill. Ditto for timbers in the sub-foor where they abut the cill.

I really wouldn't stint on the replacement timber . hardwood will serve you better thand soft. See what a proper timber merchant has to offer rather than a general builders merchant like Jewsons (Most cills I've seen ar 6x2).
I think the best you can hope for on this job is an upmarket bodge, so good luck!

Cheers for the advice cmother1,
I'm not sure of the abbreviation D/G, I assume you mean the Double Glazing units. It looks like it's all one unit, I don't see any obvious means of taking the Double glazing out but then I haven't looked that hard yet.

I'd agree with you about weight of the glass, had some small units for a external door, they were much heavier than they looked!.

I 'd had decided to use a hardwood specialist, they would charge roughly the same as a general builders merchants, though they would cut the profile to fit exactly to measure and had a better range of hardwoods.

Thanks for the tips on keeping an eye out on the rotten uprights, though the sub-floor (I assume you mean the bit that the cill sits on) is not wooden so I think I'm okay there.

Cheers again

Hi and good luck again!

Final tips: Be careful not to bow the new cill upwards in the middle: you won't be able to get the D/G panels back in if you do.

Attach the uprights to the new cill by skew screwing from the inside only. If you go in from the outside you're just inviting the weather to get in.

If you can stand the smell give all the vulnerable timbers a 5 star timber treatment. It'll dry eventually and you can then apply your preferred finish.

You're a brave man!

Weekend just gone, went ahead and replaced the cill.

Treated 3 coats of stain/waterpoof before beginning the fit, used a hardwood cill

When I cleared out the old cill I put wedges in which luckily held the partio door/frame up. Though when taking the the wedges out the centre of the patio door/frame dropped a fraction so that the doors wouldn't slide shut. Also the drop meant that the gap was a wee bit too narrow to allow the new cill in.

Solution:
* Put the wedges back in (from the inside of the building) under the patio door frame so that the doors were able to slide shut.
* Cleared out all the old mortar that was sat ontop of the damp proof course, so the gap was bigger that the new cill.
* Spread a new layer of mortar ontop of the damp proof course where it was between the wedges.
* Then from the outside of the building; tapped/bashed (using a block of would, not the hammer directly) the new cill under the patio doors, making sure to keep it butted up to the top of the gap. As the cill got tapped in, the wedges were pushed out from under the door, ending up on the inside of the building. Any excess mortar was also pushed inside the building and could be cleaned up afterwards.

I found screw holes in the base of the frame so was able to screw down through the frame into the cill to keep it in place, though its a tight fit and I doubt it would have needed them.

Looks good, Looks tight, Sealed the outside. Fingers crossed that It's good, though I reckon if it rots out, it will take years so not bad for a first timer.

Cheers

Well done. Sounds like you've made good as well as you could have hoped for. I'm sure the job will see me out!