DPC corner windows

jimmytom

Hi All,

I'm currently constructing house and am at wall plate level. I have 3 corner windows which each have a steel corner lintel above - typical catnic type corner lintel and post system. I have noticed however that no DPC was installed above the lintels in question. Will the lintels which have a splayed section satisfy the dpc tray which is normally required above window.

any thoughts much appreciated

sydthebeat

personally i wouldnt accept that. Where does the moisture which may run down the face of the inner leaf go? there needs to be a continuous step from inner leaf to outer.

depends on the type though, mostly we use the 'open back' type here where the inner block starts behind the lintel... with the 'box' type the inner block starts over the lintel, and in that case it may be ok.

jimmytom

sydthebeat wrote: »

personally i wouldnt accept that. Where does the moisture which may run down the face of the inner leaf go? there needs to be a continuous step from inner leaf to outer.

depends on the type though, mostly we use the 'open back' type here where the inner block starts behind the lintel... with the 'box' type the inner block starts over the lintel, and in that case it may be ok.

cheers for that. Its the open back type alright - inner leaf behind lintel, insulated steel lintel and then outer leaf to front. Ya I'm concerned about moisture ingressing along the inner leaf. Could an impermeable membrane be fixed on internal wall behind lintel and lapped under window head to outside to eliminate mositure ingressing? only other option i suppose is to knock out blocks above lintel and put in a dpc tray although how easy that will be is another matter

sydthebeat

any chance of a pic?

can a dpc be introduced at this stage? in theory all it has to do is to be fixed to the sloped section of the lintel

jimmytom

sydthebeat wrote: »

any chance of a pic?

can a dpc be introduced at this stage? in theory all it has to do is to be fixed to the sloped section of the lintel

i've attached pic. I'm ready to accept hollowcore on Thursday so walls have been built up to this level, thats why I have issue with now introducing DPC at this stage. I've also attached a section of the lintel as per suppliers detail - only difference being that my external leaf is block and that the cavity will be pumped. I am also fixing a 2 inch insulated plasterboard to internal leaf.

sydthebeat

What width of cavity have you? what type of insulation are you installing?

is that a cavity closer or concrete soap bar two courses over the head on the RHS? In other words, how accessible is the lintel?

jimmytom

sydthebeat wrote: »

What width of cavity have you? what type of insulation are you installing?

is that a cavity closer or concrete soap bar two courses over the head on the RHS? In other words, how accessible is the lintel?

Width of cavity is 100mm to be pumped. That is a brick two courses over the head on the RHS. Hollowcore will be spanning from this side of house. Cavity is accessible at the moment

esox28

have you found a way to insulate that pole, from what the steel lintel supplier say you can drill and insert expanding foam into the pole which will only prevent condensation appearing on internal pole side, but this dosent get away from a large thermal bridge as far as I know the windows just abut to the pole.
I have the same lintel sitting on the ground awaiting further instructions and blockwork:)

sydthebeat

knock top layer of block / brick off and drop dpc down ontop lintel. Keep in place with wedges of insulation, relay blockwork.

judging by the pic i assume this is in the west somewhere... more of a reason not to take a chance.

worst case scenario wind driven rain causes moisture on inner leaf, which drains down to internal window head and shows a constant wet spot... over 3 window heads... i wouldnt be a happy customer to see that.

jimmytom

esox28 wrote: »

have you found a way to insulate that pole, from what the steel lintel supplier say you can drill and insert expanding foam into the pole which will only prevent condensation appearing on internal pole side, but this dosent get away from a large thermal bridge as far as I know the windows just abut to the pole.
I have the same lintel sitting on the ground awaiting further instructions and blockwork:)

best solution at present for me is to box out around pole with 25mm high density insulation. Pole is 75mm shs so this will work re cavity for me. I don't see benefit of drilling column and pumping expanding foam as condensation will occur due to cold wrapping around pole and then reacting to warmer air inside. my box solution will have to suffice for me

esox28

yes I see what you are doing, but my pole had to be 100mm so no room really to box the internal section in.


I think pumping it is based on the same principle of the insulated lintel that the steel is warmed to the same temp as room and which dosent create a due point (condensation) on the pole.

will you get the window guys to box the external part of the insulation or have you something elce in mind?

jimmytom

esox28 wrote: »

yes I see what you are doing, but my pole had to be 100mm so no room really to box the internal section in.


I think pumping it is based on the same principle of the insulated lintel that the steel is warmed to the same temp as room and which dosent create a due point (condensation) on the pole.

will you get the window guys to box the external part of the insulation or have you something elce in mind?

my window suppliers will box around insulation with PVC cladding similar to window frames - I prob will drill and pump post also.

esox28

thanks guys... just got the he-b-ge-bees and am heading to site to see that I have a dpc over the steel lintels:eek:

jimmytom

esox28 wrote: »

thanks guys... just got the he-b-ge-bees and am heading to site to see that I have a dpc over the steel lintels:eek:

do and quick! best of luck

mickdw

On a seperate note, I would recommend that great car is taken when fitting the cill dpc considering the pole location.

jimmytom

sydthebeat wrote: »

knock top layer of block / brick off and drop dpc down ontop lintel. Keep in place with wedges of insulation, relay blockwork.

judging by the pic i assume this is in the west somewhere... more of a reason not to take a chance.

worst case scenario wind driven rain causes moisture on inner leaf, which drains down to internal window head and shows a constant wet spot... over 3 window heads... i wouldnt be a happy customer to see that.

cheers for the advice

jimmytom

sydthebeat wrote: »

knock top layer of block / brick off and drop dpc down ontop lintel. Keep in place with wedges of insulation, relay blockwork.

judging by the pic i assume this is in the west somewhere... more of a reason not to take a chance.

worst case scenario wind driven rain causes moisture on inner leaf, which drains down to internal window head and shows a constant wet spot... over 3 window heads... i wouldnt be a happy customer to see that.

hollowcore is on so no go with taking off that block/brick. Was thinking of using butyl sealant tape/membrane as adhesive to allow me to fix DPC to inner leaf and then drop DPC onto lintel with wedge of insulation as you had mentioned. might work